PT-symmetry of coupled fiber lasers

NASA Astrophysics Data System (ADS)

Smirnov, Sergey V.; Churkin, Dmitry V.; Makarenko, Maxim; Vatnik, Ilya; Suchkov, Sergey V.; Sukhorukov, Andrey A.

2017-10-01

In this work, we propose a concept of a coupled fiber laser exhibiting PT-symmetry properties. We consider a system operated via Raman gain. The scheme comprises two identical fiber loops (ring cavities) connected by means of two fiber couplers with variable phase shift between them. We show that by changing the phase shift one can switch between generation regimes, realizing either PT-symmetric or PT-broken solution. Furthermore, the paper investigates some peculiarities of the system such as power oscillations and the role of nonlinear phase shift in fiber rings.

An Extrinsic Fabry-Perot Interferometric Sensor using Intermodal Phase Shifting and Demultiplexing of the Propagating Modes in a Few-Mode Fiber

NASA Astrophysics Data System (ADS)

Chatterjee, Julius

This dissertation demonstrates a fiber-optic phase shifted Fabry-Perot interferometer (PS-FPI) as a sensor using modal demultiplexing. Single wavelength Fabry-Perot interferometers suffer from fringe ambiguity and loss of sensitivity at fringe extremes. These hindrances cause it to be a secondary choice when being selected for a measurement task at hand, and more often than not, white light based sensors are selected in favor of the single wavelength Fabry-Perot sensors. This work aims to introduce a technique involving the demultiplexing of the propagating linearly polarized (LP) modes in few mode fibers to obtain two fringe systems from the same sensing cavity. This results in a few-mode interferometer that effectively has two to three orders of magnitude higher perturbation sensitivity than a conventional few mode interferometer for the same sensing region. In this work, two different modal demultiplexing techniques (MD) are used to demodulate the propagating modes and to obtain two fringe sets. These output fringe sets are shifted in phase with respect to each other by a phase shift due to the propagation of the modes in the fiber-optic layout. A method of controlling this phase shift by straining a length of a two mode fiber located separate from the PS-FPI cavity is demonstrated and corresponding changes in phase shifts are shown. The results show a controllable phase shift for both the MD techniques, which is useful in sensing by permitting quadrature demodulation of interferometric fringes and also results in a novel few-mode sensing system having more than two orders of magnitude sensitivity than conventional few-mode devices.

Demonstration of differential phase-shift keying demodulation at 10 Gbit/s optimal fiber Bragg grating filters.

PubMed

Gatti, Davide; Galzerano, Gianluca; Laporta, Paolo; Longhi, Stefano; Janner, Davide; Guglierame, Andrea; Belmonte, Michele

2008-07-01

Optimal demodulation of differential phase-shift keying signals at 10 Gbit/s is experimentally demonstrated using a specially designed structured fiber Bragg grating composed by Fabry-Perot coupled cavities. Bit-error-rate measurements show that, as compared with a conventional Gaussian-shaped filter, our demodulator gives approximately 2.8 dB performance improvement.

Advanced simulation study on bunch gap transient effect

NASA Astrophysics Data System (ADS)

Kobayashi, Tetsuya; Akai, Kazunori

2016-06-01

Bunch phase shift along the train due to a bunch gap transient is a concern in high-current colliders. In KEKB operation, the measured phase shift along the train agreed well with a simulation and a simple analytical form in most part of the train. However, a rapid phase change was observed at the leading part of the train, which was not predicted by the simulation or by the analytical form. In order to understand the cause of this observation, we have developed an advanced simulation, which treats the transient loading in each of the cavities of the three-cavity system of the accelerator resonantly coupled with energy storage (ARES) instead of the equivalent single cavities used in the previous simulation, operating in the accelerating mode. In this paper, we show that the new simulation reproduces the observation, and clarify that the rapid phase change at the leading part of the train is caused by a transient loading in the three-cavity system of ARES. KEKB is being upgraded to SuperKEKB, which is aiming at 40 times higher luminosity than KEKB. The gap transient in SuperKEKB is investigated using the new simulation, and the result shows that the rapid phase change at the leading part of the train is much larger due to higher beam currents. We will also present measures to mitigate possible luminosity reduction or beam performance deterioration due to the rapid phase change caused by the gap transient.

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

Scheinker, Alexander

A recently developed form of extremum seeking for time-varying systems is implemented in hardware for the resonance control of radio-frequency cavities without phase measurements. Normal conducting RF cavity resonance control is performed via a slug tuner, while superconducting TESLA-type cavity resonance control is performed via piezo actuators. The controller maintains resonance by minimizing reflected power by utilizing model-independent adaptive feedback. Unlike standard phase-measurement-based resonance control, the presented approach is not sensitive to arbitrary phase shifts of the RF signals due to temperature-dependent cable length or phasemeasurement hardware changes. The phase independence of this method removes common slowly varying drifts andmore » required periodic recalibration of phase-based methods. A general overview of the adaptive controller is presented along with the proof of principle experimental results at room temperature. Lastly, this method allows us to both maintain a cavity at a desired resonance frequency and also to dynamically modify its resonance frequency to track the unknown time-varying frequency of an RF source, thereby maintaining maximal cavity field strength, based only on power-level measurements.« less

Multimode excitation-induced phase shifts in intrinsic Fabry-Perot interferometric fiber sensor spectra.

PubMed

Ma, Cheng; Wang, Anbo

2010-09-01

We report the modal analysis of optical fiber single-mode-multimode-single-mode intrinsic Fabry-Perot interferometer sensors. The multimode nature of the Fabry-Perot cavity gives rise to an additional phase term in the spectrogram due to intermodal dispersion-induced wavefront distortion, which could significantly affect the cavity length demodulation accuracy. By using an exact model to analyze the modal behavior, this phase term is explained by employing a rotating vector approach. Comparison of the theoretical analysis with experimental results is presented.

Testing of cavity attenuation phase shift technology for siting near-road NO2 monitors.

DOT National Transportation Integrated Search

2015-07-01

Recent research has identified the public health importance of air pollution exposures : near busy roadways. As a result, EPA significantly revised its NO2 air quality standard in 2010. : The current regulatory focus has shifted from assessment of lo...

Femtosecond-pulse inscription of fiber Bragg gratings with single or multiple phase-shifts in the structure

NASA Astrophysics Data System (ADS)

Wolf, Alexey; Dostovalov, Alexandr; Skvortsov, Mikhail; Raspopin, Kirill; Parygin, Alexandr; Babin, Sergey

2018-05-01

In this work, long high-quality fiber Bragg gratings with phase shifts in the structure are inscribed directly in the optical fiber by point-by-point technique using femtosecond laser pulses. Phase shifts are introduced during the inscription process with a piezoelectric actuator, which rapidly shifts the fiber along the direction of its movement in a chosen point of the grating with a chosen shift value. As examples, single and double π phase shifts are introduced in fiber Bragg gratings with a length up to 34 mm in passive fibers, which provide corresponding transmission peaks with bandwidth less than 1 pm. It is shown that 37 mm π -phase-shifted grating inscribed in an active Er-doped fiber forms high-quality DFB laser cavity generating single-frequency radiation at 1550 nm with bandwidth of 20 kHz and signal-to-noise ratio of >70 dB. The inscription technique has a high degree of performance and flexibility and can be easily implemented in fibers of various types.

Measuring the complex admittance and tunneling rate of a germanium hut wire hole quantum dot

NASA Astrophysics Data System (ADS)

Li, Yan; Li, Shu-Xiao; Gao, Fei; Li, Hai-Ou; Xu, Gang; Wang, Ke; Liu, He; Cao, Gang; Xiao, Ming; Wang, Ting; Zhang, Jian-Jun; Guo, Guo-Ping

2018-05-01

We investigate the microwave reflectometry of an on-chip reflection line cavity coupled to a Ge hut wire hole quantum dot. The amplitude and phase responses of the cavity can be used to measure the complex admittance and evaluate the tunneling rate of the quantum dot, even in the region where transport signal through the quantum dot is too small to be measured by conventional direct transport means. The experimental observations are found to be in good agreement with a theoretical model of the hybrid system based on cavity frequency shift and linewidth shift. Our experimental results take the first step towards fast and sensitive readout of charge and spin states in Ge hut wire hole quantum dot.

Silicon graphene waveguide tunable broadband microwave photonics phase shifter.

PubMed

Capmany, José; Domenech, David; Muñoz, Pascual

2014-04-07

We propose the use of silicon graphene waveguides to implement a tunable broadband microwave photonics phase shifter based on integrated ring cavities. Numerical computation results show the feasibility for broadband operation over 40 GHz bandwidth and full 360° radiofrequency phase-shift with a modest voltage excursion of 0.12 volt.

An Ultra-Sensitive Electrometer based on the Cavity-Embedded Cooper-Pair Transistor

NASA Astrophysics Data System (ADS)

Li, Juliang; Miller, Marco; Rimberg, Alex

2015-03-01

We discuss use of a cavity-embedded Cooper-pair transistor (cCPT) as a potentially quantum-limited electrometer. The cCPT consists of a Cooper pair transistor placed at the voltage antinode of a 5.7 GHz shorted quarter-wave resonator so that the CPT provides a galvanic connection between the cavity's central conductor and ground plane. The quantum inductance of the CPT, which appears in parallel with the effective inductance of the cavity resonance, can be modulated by application of either a gate voltage to the CPT island or a flux bias to the CPT/cavity loop. Changes in the CPT inductance shift the cavity resonant frequency, and therefore the phase of a microwave signal reflected from the cavity. The reflected wave is amplified by both SLUG and HEMT amplifiers before its phase is measured. Results of recent measurements on the cCPT electrometer will be compared with theoretical predictions. This work was supported by the NSF under Grant No. DMR-1104821, by the ARO under Contract No, W911NF-13-1-0377 and by AFOSR/DARPA under Agreement No. FA8750-12-2-0339.

Nanometric holograms based on a topological insulator material.

PubMed

Yue, Zengji; Xue, Gaolei; Liu, Juan; Wang, Yongtian; Gu, Min

2017-05-18

Holography has extremely extensive applications in conventional optical instruments spanning optical microscopy and imaging, three-dimensional displays and metrology. To integrate holography with modern low-dimensional electronic devices, holograms need to be thinned to a nanometric scale. However, to keep a pronounced phase shift modulation, the thickness of holograms has been generally limited to the optical wavelength scale, which hinders their integration with ultrathin electronic devices. Here, we break this limit and achieve 60 nm holograms using a topological insulator material. We discover that nanometric topological insulator thin films act as an intrinsic optical resonant cavity due to the unequal refractive indices in their metallic surfaces and bulk. The resonant cavity leads to enhancement of phase shifts and thus the holographic imaging. Our work paves a way towards integrating holography with flat electronic devices for optical imaging, data storage and information security.

Cavity-enhanced optical bottle beam as a mechanical amplifier

NASA Astrophysics Data System (ADS)

Freegarde, Tim; Dholakia, Kishan

2002-07-01

We analyze the resonant cavity enhancement of a hollow ``optical bottle beam'' for the dipole-force trapping of dark-field-seeking species. We first improve upon the basic bottle beam by adding further Laguerre-Gaussian components to deepen the confining potential. Each of these components itself corresponds to a superposition of transverse cavity modes, which are then enhanced simultaneously in a confocal cavity to produce a deep optical trap needing only a modest incident power. The response of the trapping field to displacement of the cavity mirrors offers an unusual form of mechanical amplifier in which the Gouy phase shift produces an optical Vernier scale between the Laguerre-Gaussian beam components.

Measuring atmospheric visibility cavity attenuated phase shift spectroscopy

NASA Astrophysics Data System (ADS)

Jie, Guo; Ye, Shan-Shan; Yang, Xiao; Han, Ye-Xing; Tang, Huai-Wu; Yu, Zhi-Wei

2016-10-01

In the paper, an accurate and sensitive cavity attenuated phase shift spectroscopy (CAPS) system was used to monitor the atmospheric visibility coefficient in urban areas. The CAPS system, which detects the atmospheric visibility within a 10 nm bandpass centered at 532 nm, comprises a green LED with center wavelength in 532nm, a resonant optical cavity (36 cm length), a Photo Multiplier Tube detector and a lock in amplifier. The performance of the CAPS system was evaluated by measuring of the stability and response of the system. The minima ( 0.06 Mm-1) in the Allan plots show the optimum average time( 80s) for optimum detection performance of the CAPS system. The 2L/min flow rate, the CAPS system rise and fall response time is about 15 s, so as to realize the fast measurement of visibility. By comparing the forward scatter visibility meter measurement results, the CAPS system measurement results are verified reliably, and have high precision measurement. These figures indicate that this method has the potential to become one of the most sensitive on-line analytical techniques for atmospheric visibility detection.

Phase stable RF transport system

DOEpatents

Curtin, Michael T.; Natter, Eckard F.; Denney, Peter M.

1992-01-01

An RF transport system delivers a phase-stable RF signal to a load, such as an RF cavity of a charged particle accelerator. A circuit generates a calibration signal at an odd multiple frequency of the RF signal where the calibration signal is superimposed with the RF signal on a common cable that connects the RF signal with the load. Signal isolating diplexers are located at both the RF signal source end and load end of the common cable to enable the calibration to be inserted and extracted from the cable signals without any affect on the RF signal. Any phase shift in the calibration signal during traverse of the common cable is then functionally related to the phase shift in the RF signal. The calibration phase shift is used to control a phase shifter for the RF signal to maintain a stable RF signal at the load.

Manipulating Nonlinear Emission and Cooperative Effect of CdSe/ZnS Quantum Dots by Coupling to a Silver Nanorod Complex Cavity

PubMed Central

Nan, Fan; Cheng, Zi-Qiang; Wang, Ya-Lan; Zhang, Qing; Zhou, Li; Yang, Zhong-Jian; Zhong, Yu-Ting; Liang, Shan; Xiong, Qihua; Wang, Qu-Quan

2014-01-01

Colloidal semiconductor quantum dots have three-dimensional confined excitons with large optical oscillator strength and gain. The surface plasmons of metallic nanostructures offer an efficient tool to enhance exciton-exciton coupling and excitation energy transfer at appropriate geometric arrangement. Here, we report plasmon-mediated cooperative emissions of approximately one monolayer of ensemble CdSe/ZnS quantum dots coupled with silver nanorod complex cavities at room temperature. Power-dependent spectral shifting, narrowing, modulation, and amplification are demonstrated by adjusting longitudinal surface plasmon resonance of silver nanorods, reflectivity and phase shift of silver nanostructured film, and mode spacing of the complex cavity. The underlying physical mechanism of the nonlinear excitation energy transfer and nonlinear emissions are further investigated and discussed by using time-resolved photoluminescence and finite-difference time-domain numerical simulations. Our results suggest effective strategies to design active plasmonic complex cavities for cooperative emission nanodevices based on semiconductor quantum dots. PMID:24787617

Nanometric holograms based on a topological insulator material

PubMed Central

Yue, Zengji; Xue, Gaolei; Liu, Juan; Wang, Yongtian; Gu, Min

2017-01-01

Holography has extremely extensive applications in conventional optical instruments spanning optical microscopy and imaging, three-dimensional displays and metrology. To integrate holography with modern low-dimensional electronic devices, holograms need to be thinned to a nanometric scale. However, to keep a pronounced phase shift modulation, the thickness of holograms has been generally limited to the optical wavelength scale, which hinders their integration with ultrathin electronic devices. Here, we break this limit and achieve 60 nm holograms using a topological insulator material. We discover that nanometric topological insulator thin films act as an intrinsic optical resonant cavity due to the unequal refractive indices in their metallic surfaces and bulk. The resonant cavity leads to enhancement of phase shifts and thus the holographic imaging. Our work paves a way towards integrating holography with flat electronic devices for optical imaging, data storage and information security. PMID:28516906

Coherent Rabi Dynamics of a Superradiant Spin Ensemble in a Microwave Cavity

NASA Astrophysics Data System (ADS)

Rose, B. C.; Tyryshkin, A. M.; Riemann, H.; Abrosimov, N. V.; Becker, P.; Pohl, H.-J.; Thewalt, M. L. W.; Itoh, K. M.; Lyon, S. A.

2017-07-01

We achieve the strong-coupling regime between an ensemble of phosphorus donor spins in a highly enriched 28Si crystal and a 3D dielectric resonator. Spins are polarized beyond Boltzmann equilibrium using spin-selective optical excitation of the no-phonon bound exciton transition resulting in N =3.6 ×1 013 unpaired spins in the ensemble. We observe a normal mode splitting of the spin-ensemble-cavity polariton resonances of 2 g √{N }=580 kHz (where each spin is coupled with strength g ) in a cavity with a quality factor of 75 000 (γ ≪κ ≈60 kHz , where γ and κ are the spin dephasing and cavity loss rates, respectively). The spin ensemble has a long dephasing time (T2*=9 μ s ) providing a wide window for viewing the dynamics of the coupled spin-ensemble-cavity system. The free-induction decay shows up to a dozen collapses and revivals revealing a coherent exchange of excitations between the superradiant state of the spin ensemble and the cavity at the rate g √{N }. The ensemble is found to evolve as a single large pseudospin according to the Tavis-Cummings model due to minimal inhomogeneous broadening and uniform spin-cavity coupling. We demonstrate independent control of the total spin and the initial Z projection of the psuedospin using optical excitation and microwave manipulation, respectively. We vary the microwave excitation power to rotate the pseudospin on the Bloch sphere and observe a long delay in the onset of the superradiant emission as the pseudospin approaches full inversion. This delay is accompanied by an abrupt π -phase shift in the peusdospin microwave emission. The scaling of this delay with the initial angle and the sudden phase shift are explained by the Tavis-Cummings model.

Acceleration Strain Transducer with Increased Sensitivity

DTIC Science & Technology

2009-09-22

utilizing a fiber laser sensor. The fiber laser accelerometer 10 includes a fiber laser 12. Fiber laser 12 can be either a Fabry - Perot type cavity...fiber laser or a distributed feedback fiber laser. In a Fabry - Perot type fiber laser, the laser cavity is a length of erbium- doped optical fiber...designs can produce the same type of signal. A receiver 26 receives the phase shifted signal. Receiver 26 is capable of demodulating and detecting

Ultrathin reflective acoustic metasurface based on the synergetic coupling of resonant cavity and labyrinthine beams

NASA Astrophysics Data System (ADS)

Han, S. K.; Zhang, W.; Ma, G. J.; Wu, C. W.; Chen, Z.

2018-05-01

We propose a reflective acoustic metasurface by taking advantage of the synergetic coupling of two kinds of widely used elements, the resonant cavity and the labyrinthine beam. A full 2π phase shift range can be obtained by varying the neck width. The structure manipulates the reflective waves on a very deep subwavelength scale with the thickness being only 1/50 of the wavelength, which eliminates the enormous obstacle in low frequency applications. The synergetic coupling of the resonant cavity and the inner labyrinthine beams provide a useful guide for the design of acoustic metasurfaces.

Overlapping double potential wells in a single optical microtube cavity with vernier-scale-like tuning effect

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

Madani, A.; Schmidt, O. G.; Material Systems for Nanoelectronics, Chemnitz University of Technology, Reichenhainer Str. 70, 09107 Chemnitz

2016-04-25

Spatially and temporally overlapping double potential wells are realized in a hybrid optical microtube cavity due to the coexistence of an aggregate of luminescent quantum dots embedded in the tube wall and the cone-shaped tube's geometry. The double potential wells produce two independent sets of optical modes with different sets of mode numbers, indicating phase velocity separation for the modes overlapping at the same frequency. The overlapping mode position can be tuned by modifying the tube cavity, where these mode sets shift with different magnitudes, allowing for a vernier-scale-like tuning effect.

Fiber Optic Laser Accelerometer

DTIC Science & Technology

2007-11-06

embodiment of a fiber laser accelerometer 10. The fiber laser accelerometer 10 includes a fiber laser 12. Fiber laser 12 can be either a Fabry - Perot type...cavity fiber laser or a distributed feedback fiber laser. In a 4 Attorney Docket No. 97966 Fabry - Perot type fiber laser, the laser cavity is a length...type of signal. A receiver 26 receives the phase shifted signal. Receiver 26 is capable of demodulating and detecting the signal from the fiber laser by

Acceleration Strain Transducer

DTIC Science & Technology

2007-11-05

accelerometer 10 includes a fiber laser 12. Fiber laser 12 can be either a Fabry - Perot type cavity fiber laser or a distributed feedback fiber laser. In a... Fabry - Perot type fiber laser, the laser cavity is a length of erbium- doped optical fiber with a Bragg grating written in the fiber core at either end of...the phase shifted signal. Receiver 26 is capable of demodulating and detecting the signal from the fiber laser by various methods well known in the

Dispersive bi-stability in a vertical microcavity-based saturable absorber due to photo-thermal effect and initial phase-detuning

NASA Astrophysics Data System (ADS)

Pradhan, R.; Saha, S.; Datta, P. K.

2013-01-01

Round-trip phase-shifts with intensity of an input signal due to saturable index change and optically induced thermal effects in a vertical cavity semiconductor (quantum wells) saturable absorber (VCSSA) are investigated analytically to observe counter-clockwise bi-stability in transmission mode and clockwise bi-stability in reflection mode. Simultaneous effects of Kerr nonlinearity and cavity heating on resonance wavelength-shift of the VCSSA micro-cavity are investigated. It is found that these bi-stable characteristics are possible to the absorption edge of nonlinear material for long wavelength side operations of low intensity resonance wavelength of the micro-cavity, where dispersion of absorption and refraction are neglected over a small range of optical wavelength tuning (δλ˜10 nm). Simulations are carried out to find out optimized parameters of the device for bi-stable characteristics. Operations are demonstrated for InGaAs/InP quantum wells based VCSSA with low intensity resonance wavelength of 1570 nm. For counter-clockwise bi-stable switching at working wavelength of 1581 nm, an input intensity variation of 0.79IS is required with top (Rt) and back DBR reflectivity (Rb) of 91% and 93%, respectively, where IS represents the absorption saturation intensity of nonlinear medium. Whereas, the clockwise bi-stability occurs at 0.22IS for working wavelength of 1578 nm with Rt of 90% and Rb of 98%, respectively.

Fiber optic extrinsic Fabry-Perot accelerometer using laser emission frequency modulated phase generated carrier demodulation scheme

NASA Astrophysics Data System (ADS)

Wang, Dai-Hua; Jia, Ping-Gang

2013-05-01

The principle of a fiber optic Fabry-Perot (F-P) accelerometer (FOFPA) system using the laser emission frequency modulated phase generated carrier (FMPGC) demodulation scheme is first described and experimentally demonstrated. The F-P cavity, which is constituted by placing the end face of a gradient-index lens in parallel with the reflector on the inertial mass, directly translates the inertial mass's displacement generated by the measured acceleration into phase shifts of the interference output from the F-P cavity. An FMPGC demodulation scheme based on the arctangent (Arctan) algorithm is adapted to demodulate the phase shifts. The sensing model for the FOFPA system using the FMPGC-Arctan demodulation scheme is established and the sensing characteristics are theoretically analyzed. On these bases, the FOFPA is designed and fabricated and a prototyping system is built and tested. The results indicate that: (1) the nonlinearity of the FOFPA system using the FMPGC-Arctan demodulation scheme is less than 0.58%, (2) the resonant frequency, on-axial sensitivity, and resolution are 393 Hz, 13.11 rad/g, and 450 μ, respectively, and (3) the maximum deviation of the phase sensitivity of the FOFPA within the temperature range of 30 to 80°C is 0.49 dB re 1 rad/g.

Theoretical Investigation of Tunable Goos-Hänchen Shifts in a Four-Level Quantum System

NASA Astrophysics Data System (ADS)

Jafarzadeh, Hossein; Payravi, Mohammad

2018-05-01

Goos-Hänchen (GH) shifts in the reflected and transmitted light have been discussed in a cavity with four-level quantum system. It is realized that the refraction index of intracavity medium can be negative by manipulating the external coherent laser fields. For the negative refraction index of intracavity medium, the GH shifts of reflected and transmitted light beams have been analyzed in a parametric condition. It is found that due to modulation of laser signals and relative phase between applied fields, large and tunable GH shifts in reflected and transmitted light beams can be obtained.

Resonant tunneling of surface plasmon polariton in the plasmonic nano-cavity.

PubMed

Park, Junghyun; Kim, Hwi; Lee, Il-Min; Kim, Seyoon; Jung, Jaehoon; Lee, Byoungho

2008-10-13

We investigate the reflection and transmission characteristics of the low-dielectric constant cut off barrier in the metal-insulator-metal (MIM) waveguide and propose a novel plasmonic nano-cavity made of two cut off barriers and the waveguide between them. It is shown that the anti-symmetric mode in the MIM waveguide with the core of the low dielectric constant below the specific value cannot be supported and this region can be regarded as a cut off barrier with high stability. The phase shift due to the reflection at the finite-length cut off barrier is calculated and the design scheme of the cavity length for the resonant tunneling is presented. The transmission spectra through the proposed nano-cavity are also discussed.

Optical bistability in a single-sided cavity coupled to a quantum channel

NASA Astrophysics Data System (ADS)

Payravi, M.; Solookinejad, Gh; Jabbari, M.; Nafar, M.; Ahmadi Sangachin, E.

2018-06-01

In this paper, we discuss the long wavelength optical reflection and bistable behavior of an InGaN/GaN quantum dot nanostructure coupled to a single-sided cavity. It is found that due to the presence of a strong coupling field, the reflection coefficient can be controlled at long wavelength, which is essential for adjusting the threshold of reflected optical bistability. Moreover, the phase shift features of the reflection pulse inside an electromagnetically induced transparency window are also discussed.

Ultrasensitive Electrometry with a Cavity-Embedded Cooper Pair Transistor

NASA Astrophysics Data System (ADS)

Rimberg, A. J.; Li, Juliang

In this experiment a cavity-embedded Cooper-pair transistor (cCPT) is used as a potentially quantum-limited electrometer. The cCPT consists of a Cooper pair transistor placed at the voltage antinode of a 5.7 GHz shorted quarter-wave resonator so that the CPT provides a galvanic connection between the cavity's central conductor and ground plane. The quantum inductance of the CPT, which appears in parallel with the effective inductance of the cavity resonance, can be modulated by application of either a gate voltage to the CPT island or a flux bias to the CPT/cavity loop. Changes in the CPT inductance shift the cavity resonant frequency, and therefore the phase of a microwave signal reflected from the cavity. The reflected wave is amplified by both SLUG and HEMT amplifiers before its phase is measured. The cCPT can also be operated as a Josephson parametric amplifier (JPA). A pump tone at 11.4 GHz sent into the flux bias line has been shown to provide about 10dB gain. The possibility of parametrically amplifying the side bands produced by a charge detection measurement, thereby increasing the overall sensitivity of the cCPT, will also be investigated. Supported by Grants ARO W911NF-13-10377 and NSF DMR 1507400.

High sensitivity liquid phase measurements using broadband cavity enhanced absorption spectroscopy (BBCEAS) featuring a low cost webcam based prism spectrometer.

PubMed

Qu, Zhechao; Engstrom, Julia; Wong, Donald; Islam, Meez; Kaminski, Clemens F

2013-11-07

Cavity enhanced techniques enable high sensitivity absorption measurements in the liquid phase but are typically more complex, and much more expensive, to perform than conventional absorption methods. The latter attributes have so far prevented a wide spread use of these methods in the analytical sciences. In this study we demonstrate a novel BBCEAS instrument that is sensitive, yet simple and economical to set up and operate. We use a prism spectrometer with a low cost webcam as the detector in conjunction with an optical cavity consisting of two R = 0.99 dielectric mirrors and a white light LED source for illumination. High sensitivity liquid phase measurements were made on samples contained in 1 cm quartz cuvettes placed at normal incidence to the light beam in the optical cavity. The cavity enhancement factor (CEF) with water as the solvent was determined directly by phase shift cavity ring down spectroscopy (PS-CRDS) and also by calibration with Rhodamine 6G solutions. Both methods yielded closely matching CEF values of ~60. The minimum detectable change in absorption (αmin) was determined to be 6.5 × 10(-5) cm(-1) at 527 nm and was limited only by the 8 bit resolution of the particular webcam detector used, thus offering scope for further improvement. The instrument was used to make representative measurements on dye solutions and in the determination of nitrite concentrations in a variation of the widely used Griess Assay. Limits of detection (LOD) were ~850 pM for Rhodamine 6G and 3.7 nM for nitrite, respectively. The sensitivity of the instrument compares favourably with previous cavity based liquid phase studies whilst being achieved at a small fraction of the cost hitherto reported, thus opening the door to widespread use in the community. Further means of improving sensitivity are discussed in the paper.

Carrier-envelope phase control by a composite plate.

PubMed

Ell, Richard; Birge, Jonathan R; Araghchini, Mohammad; Kärtner, Franz X

2006-06-12

We demonstrate a new concept to vary the carrier-envelope phase of a mode-locked laser by a composite plate while keeping all other pulse parameters practically unaltered. The effect is verified externally in an interferometric autocorrelator, as well as inside the cavity of an octave-spanning femtosecond oscillator. The carrier-envelope frequency can be shifted by half the repetition rate with negligible impact on pulse spectrum and energy.

Two-pass-internal second-harmonic generation using a prism coupler.

NASA Technical Reports Server (NTRS)

Gonzalez, D. G.; Nieh, S. T. K.; Steier, W. H.

1973-01-01

A dispersive quartz prism is used to couple the total second harmonic generated in both directions by an internal cavity frequency doubler. The study shows that the dispersion of air and mirror reflection phase shifts can be compensated for by a slight nonphase match condition in the doubler.

Synchronization of pulses from mode-locked lasers

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

Harvey, G.T.

A study of the synchronization of mode-locked lasers is presented. In particular, we investigate the timing of the laser output pulses with respect to the radio frequency (RF) signal driving the mode-locking elements in the laser cavity. Two types of mode-locked lasers are considered: a cw loss-modulated mode-locked argon ion laser; and a q-switched active-passive mode-locked Nd:YAG laser. We develop theoretical models for the treatment of laser pulse synchronization in both types of lasers. Experimental results are presented on a combined laser system that synchronizes pulses from both an argon ion and a Nd:YAG laser by using a common RFmore » signal to drive independent mode-lockers in both laser cavities. Shot to shot jitter as low as 18 ps (RMS) was measured between the output pulses from the two lasers. The theory of pulse synchronization for the cw loss-modulated mode-locked argon ion laser is based on the relationship between the timing of the mode-locked laser pulse (with respect to the peak of the RF signal) and the length of the laser cavity. Experiments on the argon laser include the measurement of the phase shift of the mode-locked pulse as a function of cavity length and intracavity intensity. The theory of synchronization of the active-passive mode-locked Nd:YAG laser is an extension of the pulse selection model of the active-passive laser. Experiments on the active-passive Nd:YAG laser include: measurement of the early noise fluctuations; measurement of the duration of the linear build-up stage (time between laser threshold and saturation of the absorber); measurement of jitter as a function of the mode-locker modulation depth; and measurement of the output pulse phase shift as a function of cavity length.« less

In-hardware demonstration of model-independent adaptive tuning of noisy systems with arbitrary phase drift

DOE PAGES

Scheinker, Alexander; Baily, Scott; Young, Daniel; ...

2014-08-01

In this work, an implementation of a recently developed model-independent adaptive control scheme, for tuning uncertain and time varying systems, is demonstrated on the Los Alamos linear particle accelerator. The main benefits of the algorithm are its simplicity, ability to handle an arbitrary number of components without increased complexity, and the approach is extremely robust to measurement noise, a property which is both analytically proven and demonstrated in the experiments performed. We report on the application of this algorithm for simultaneous tuning of two buncher radio frequency (RF) cavities, in order to maximize beam acceptance into the accelerating electromagnetic fieldmore » cavities of the machine, with the tuning based only on a noisy measurement of the surviving beam current downstream from the two bunching cavities. The algorithm automatically responds to arbitrary phase shift of the cavity phases, automatically re-tuning the cavity settings and maximizing beam acceptance. Because it is model independent it can be utilized for continuous adaptation to time-variation of a large system, such as due to thermal drift, or damage to components, in which the remaining, functional components would be automatically re-tuned to compensate for the failing ones. We start by discussing the general model-independent adaptive scheme and how it may be digitally applied to a large class of multi-parameter uncertain systems, and then present our experimental results.« less

Investigation on a fiber optic accelerometer based on FBG-FP interferometer

NASA Astrophysics Data System (ADS)

Lin, Chongyu; Luo, Hong; Xiong, Shuidong; Li, Haitao

2014-12-01

A fiber optic accelerometer based on fiber Bragg grating Fabry-Perot (FBG-FP) interferometer is presented. The sensor is a FBG-FP cavity which is formed with two weak fiber Bragg gratings (FBGs) in a single-mode fiber. The reflectivity of the two FBGs is 9.42% and 7.74% respectively, and the fiber between them is 10 meters long. An optical demodulation system was set up to analyze the reflected light of FBG-FP cavity. Acceleration signals of different frequencies and intensities were demodulated correctly and stably by the system. Based on analyzing the optical spectrum of weak FBG based FBG-FP cavity, we got the equivalent length of FBG-FP cavity. We used a path-matching Michelson interferometer (MI) to demodulate the acceleration signal. The visibility of the interference fringe we got was 41%~42% while the theory limit was 50%. This indicated that the difference of interferometer's two arms and the equivalent length of FBG-FP cavity were matched well. Phase generated carrier (PGC) technology was used to eliminate phase fading caused by random phase shift and Faraday rotation mirrors (FRMs) were used to eliminate polarization-induced phase fading. The accelerometer used a compliant cylinder design and its' sensitivity and frequency response were analyzed and simulated based on elastic mechanics. Experiment result showed that the accelerometer had a flat frequency response over the frequency range of 31-630Hz. The sensitivity was about 31dB (0dB=1rad/g) with fluctuation less than 1.5dB.

Ultra-narrow-linewidth erbium-doped lasers on a silicon photonics platform

NASA Astrophysics Data System (ADS)

Li, Nanxi; Purnawirman, Purnawirman; Magden, E. Salih; Singh, Gurpreet; Singh, Neetesh; Baldycheva, Anna; Hosseini, Ehsan S.; Sun, Jie; Moresco, Michele; Adam, Thomas N.; Leake, Gerald; Coolbaugh, Douglas; Bradley, Jonathan D. B.; Watts, Michael R.

2018-02-01

We report ultra-narrow-linewidth erbium-doped aluminum oxide (Al2O3:Er3+) distributed feedback (DFB) lasers with a wavelength-insensitive silicon-compatible waveguide design. The waveguide consists of five silicon nitride (SiNx) segments buried under silicon dioxide (SiO2) with a layer Al2O3:Er3+ deposited on top. This design has a high confinement factor (> 85%) and a near perfect (> 98%) intensity overlap for an octave-spanning range across near infrared wavelengths (950-2000 nm). We compare the performance of DFB lasers in discrete quarter phase shifted (QPS) cavity and distributed phase shifted (DPS) cavity. Using QPS-DFB configuration, we obtain maximum output powers of 0.41 mW, 0.76 mW, and 0.47 mW at widely spaced wavelengths within both the C and L bands of the erbium gain spectrum (1536 nm, 1566 nm, and 1596 nm). In a DPS cavity, we achieve an order of magnitude improvement in maximum output power (5.43 mW) and a side mode suppression ratio (SMSR) of > 59.4 dB at an emission wavelength of 1565 nm. We observe an ultra-narrow linewidth of ΔνDPS = 5.3 +/- 0.3 kHz for the DPS-DFB laser, as compared to ΔγQPS = 30.4 +/- 1.1 kHz for the QPS-DFB laser, measured by a recirculating self-heterodyne delayed interferometer (RSHDI). Even narrower linewidth can be achieved by mechanical stabilization of the setup, increasing the pump absorption efficiency, increasing the output power, or enhancing the cavity Q.

Gap solitons in a nonlinear quadratic negative-index cavity.

PubMed

Scalora, Michael; de Ceglia, Domenico; D'Aguanno, Giuseppe; Mattiucci, Nadia; Akozbek, Neset; Centini, Marco; Bloemer, Mark J

2007-06-01

We predict the existence of gap solitons in a nonlinear, quadratic Fabry-Pérot negative index cavity. A peculiarity of a single negative index layer is that if magnetic and electric plasma frequencies are different it forms a photonic band structure similar to that of a multilayer stack composed of ordinary, positive index materials. This similarity also results in comparable field localization and enhancement properties that under appropriate conditions may be used to either dynamically shift the band edge, or for efficient energy conversion. We thus report that an intense, fundamental pump pulse is able to shift the band edge of a negative index cavity, and make it possible for a weak second harmonic pulse initially tuned inside the gap to be transmitted, giving rise to a gap soliton. The process is due to cascading, a well-known phenomenon that occurs far from phase matching conditions that limits energy conversion rates, it resembles a nonlinear third-order process, and causes pulse compression due to self-phase modulation. The symmetry of the equations of motion under the action of either an electric or a magnetic nonlinearity suggests that both nonlinear polarization and magnetization, or a combination of both, can lead to solitonlike pulses. More specifically, the antisymmetric localization properties of the electric and magnetic fields cause a nonlinear polarization to generate a dark soliton, while a nonlinear magnetization spawns a bright soliton.

A double-fibre Fabry-Perot sensor based on modified fringe counting and direct phase demodulation

NASA Astrophysics Data System (ADS)

Li, M.; Tong, B.; Arsad, N.; Guo, J. J.

2013-09-01

A modified double-fibre Fabry-Perot cavity is developed for determination of the fringe moving direction and higher sensitivity in applications of liquid level and displacement sensors. Two fibres are integrated into a silica ferrule where the ends of the two fibres in the ferrule serve as the front surfaces of the Fabry-Perot cavities, and a diaphragm, which is replaced by a moving mirror for measurement of displacement, serves as the rear surface for both cavities in liquid level sensing. Our design has no strict requirements for a specific phase difference between the two optical paths, just a constant difference resulting from the processing error between the two fibre end positions rather than a precise optical path difference of λ/8 to judge the pattern shift direction. Experimental results demonstrate the feasibility of this approach to determining the fringe moving direction, a displacement sensitivity of 3 µm and good linearity for both applications.

Quasi-continuous frequency tunable terahertz quantum cascade lasers with coupled cavity and integrated photonic lattice.

PubMed

Kundu, Iman; Dean, Paul; Valavanis, Alexander; Chen, Li; Li, Lianhe; Cunningham, John E; Linfield, Edmund H; Davies, A Giles

2017-01-09

We demonstrate quasi-continuous tuning of the emission frequency from coupled cavity terahertz frequency quantum cascade lasers. Such coupled cavity lasers comprise a lasing cavity and a tuning cavity which are optically coupled through a narrow air slit and are operated above and below the lasing threshold current, respectively. The emission frequency of these devices is determined by the Vernier resonance of longitudinal modes in the lasing and the tuning cavities, and can be tuned by applying an index perturbation in the tuning cavity. The spectral coverage of the coupled cavity devices have been increased by reducing the repetition frequency of the Vernier resonance and increasing the ratio of the free spectral ranges of the two cavities. A continuous tuning of the coupled cavity modes has been realized through an index perturbation of the lasing cavity itself by using wide electrical heating pulses at the tuning cavity and exploiting thermal conduction through the monolithic substrate. Single mode emission and discrete frequency tuning over a bandwidth of 100 GHz and a quasi-continuous frequency coverage of 7 GHz at 2.25 THz is demonstrated. An improvement in the side mode suppression and a continuous spectral coverage of 3 GHz is achieved without any degradation of output power by integrating a π-phase shifted photonic lattice in the laser cavity.

Xenon NMR of liquid crystals confined to cylindrical nanocavities: a simulation study.

PubMed

Karjalainen, Jouni; Vaara, Juha; Straka, Michal; Lantto, Perttu

2015-03-21

Applications of liquid crystals (LCs), such as smart windows and the ubiquitous display devices, are based on controlling the orientational and translational order in a small volume of LC medium. Hence, understanding the effects of confinement to the liquid crystal phase behaviour is essential. The NMR shielding of (129)Xe atoms dissolved in LCs constitutes a very sensitive probe to the details of LC environment. Linking the experimental results to microscopic phenomena calls for molecular simulations. In this work, the NMR shielding of atomic (129)Xe dissolved in a uniaxial thermotropic LC confined to nanosized cylindrical cavities is computed from coarse-grained (CG) isobaric Monte Carlo (MC) simulations with a quantum-chemically (QC) pre-parameterised pairwise-additive model for the Xe nuclear shielding tensor. We report the results for the (129)Xe nuclear shielding and its connection to the structure and order of the LC appropriate to two different cavity sizes, as well as a comparison to the results of bulk (non-confined) simulations. We find that the confinement changes the LC phase structure dramatically and gives rise to the coexistence of varying degrees of LC order, which is reflected in the Xe shielding. Furthermore, we qualitatively reproduce the behaviour of the mean (129)Xe chemical shift with respect to temperature for atomic Xe dissolved in LC confined to controlled-pore glass materials. In the small-radius cavity the nematic - paranematic phase transition is revealed only by the anisotropic component of the (129)Xe nuclear shielding. In the larger cavity, the nematic - paranematic - isotropic transition is clearly seen in the Xe shielding. The simulated (129)Xe NMR shielding is insensitive to the smectic-A - nematic transition, since in the smectic-A phase, the Xe atoms largely occupy the imperfect layer structure near the cavity walls. The direct contribution of the cavity wall to (129)Xe nuclear shielding is dependent on the cavity size but independent of temperature. Our results show that the combination of CG simulations and a QC pre-parameterised (129)Xe NMR shielding allows efficient studies of the phase behaviour and structure of complex systems containing thousands of molecules, and brings us closer to the simulation of NMR experiments.

Mode conversion in metal-insulator-metal waveguide with a shifted cavity

NASA Astrophysics Data System (ADS)

Wang, Yueke; Yan, Xin

2018-01-01

We propose a method, which is utilized to achieve the plasmonic mode conversion in metal-insulator-metal (MIM) waveguide, theoretically. Our proposed structure is composed of bus waveguides and a shifted cavity. The shifted cavity can choose out a plasmonic mode (a- or s-mode) when it is in Fabry-Perot (FP) resonance. The length of the shifted cavity L is carefully chosen, and our structure can achieve the mode conversion between a- and s-mode in the communication region. Besides, our proposed structure can also achieve plasmonic mode-division multiplexing. All the numerical simulations are carried on by the finite element method to verify our design.

Precision requirements and innovative manufacturing for ultrahigh precision laser interferometry of gravitational-wave astronomy

NASA Astrophysics Data System (ADS)

Ni, Wei-Tou; Han, Sen; Jin, Tao

2016-11-01

With the LIGO announcement of the first direct detection of gravitational waves (GWs), the GW Astronomy was formally ushered into our age. After one-hundred years of theoretical investigation and fifty years of experimental endeavor, this is a historical landmark not just for physics and astronomy, but also for industry and manufacturing. The challenge and opportunity for industry is precision and innovative manufacturing in large size - production of large and homogeneous optical components, optical diagnosis of large components, high reflectance dielectric coating on large mirrors, manufacturing of components for ultrahigh vacuum of large volume, manufacturing of high attenuating vibration isolation system, production of high-power high-stability single-frequency lasers, production of high-resolution positioning systems etc. In this talk, we address the requirements and methods to satisfy these requirements. Optical diagnosis of large optical components requires large phase-shifting interferometer; the 1.06 μm Phase Shifting Interferometer for testing LIGO optics and the recently built 24" phase-shifting Interferometer in Chengdu, China are examples. High quality mirrors are crucial for laser interferometric GW detection, so as for ring laser gyroscope, high precision laser stabilization via optical cavities, quantum optomechanics, cavity quantum electrodynamics and vacuum birefringence measurement. There are stringent requirements on the substrate materials and coating methods. For cryogenic GW interferometer, appropriate coating on sapphire or silicon are required for good thermal and homogeneity properties. Large ultrahigh vacuum components and high attenuating vibration system together with an efficient metrology system are required and will be addressed. For space interferometry, drag-free technology and weak-light manipulation technology are must. Drag-free technology is well-developed. Weak-light phase locking is demonstrated in the laboratories while weak-light manipulation technology still needs developments.

Optimal all-optical switching of a microcavity resonance in the telecom range using the electronic Kerr effect.

PubMed

Yüce, Emre; Ctistis, Georgios; Claudon, Julien; Gérard, Jean-Michel; Vos, Willem L

2016-01-11

We have switched GaAs/AlAs and AlGaAs/AlAs planar microcavities that operate in the "Original" (O) telecom band by exploiting the instantaneous electronic Kerr effect. We observe that the resonance frequency reversibly shifts within one picosecond when the nanostructure is pumped with low-energy photons. We investigate experimentally and theoretically the role of several parameters: the material backbone and its electronic bandgap, the quality factor, and the duration of the switch pulse. The magnitude of the frequency shift is reduced when the backbone of the central λ-layer has a greater electronic bandgap compared to the cavity resonance frequency and the frequency of the pump. This observation is caused by the fact that pumping with photon energies near the bandgap resonantly enhances the switched magnitude. We thus find that cavities operating in the telecom O-band are more amenable to ultrafast Kerr switching than those operating at lower frequencies, such as the C-band. Our results indicate that the large bandgap of AlGaAs/AlAs cavity allows to tune both the pump and the probe to the telecom range to perform Kerr switching without detrimental two-photon absorption. We observe that the magnitude of the resonance frequency shift decreases with increasing quality factor of the cavity. Our model shows that the magnitude of the resonance frequency shift depends on the pump pulse duration and is maximized when the duration matches the cavity storage time to within a factor two. In our experiments, we obtain a maximum shift of the cavity resonance relative to the cavity linewidth of 20%. We project that the shift of the cavity resonance can be increased twofold with a pump pulse duration that better matches the cavity storage time. We provide the essential parameter settings for different materials so that the frequency shift of the cavity resonance can be maximized using the electronic Kerr effect.

Pollen-imprinted polyurethanes for QCM allergen sensors.

PubMed

Jenik, Michael; Seifner, Alexandra; Lieberzeit, Peter; Dickert, Franz L

2009-05-01

Molecularly imprinted polymers for detecting plant pollen were designed as artificial recognition materials for quartz crystal microbalances in the gaseous phase. Imprints of birch (diameter, 25 mum) and nettle (diameter, 15 mum) pollen can be generated by polydimethylsiloxane stamping technique as proven by atomic force microscopy. If pollen grains are able to access the cavities and thus are incorporated, the resulting sensors display Sauerbrey-like negative frequency shifts. Non-Sauerbrey behaviour can be observed as soon as pollen is prevented from entering the selective hollows: this results in grain mobility on the electrode surface leading to frequency increases. Access to the cavities is determined by the diameter ratio between pollen grains and imprints as can be revealed during cross-selectivity measurements of nettle and birch pollen imprinted layers. When the amount of pollen grains on the electrode surface exceeds the number of available imprints, the excess particles move freely, resulting in positive, non-Sauerbrey frequency shifts.

Wavelength shift in vertical cavity laser arrays on a patterned substrate

NASA Astrophysics Data System (ADS)

Eng, L. E.; Bacher, K.; Yuen, W.; Larson, M.; Ding, G.; Harris, J. S., Jr.; Chang-Hasnain, C. J.

1995-03-01

The authors demonstrate a spatially chirped emission wavelength in vertical cavity surface emitting laser (VCSEL) arrays grown by molecular beam epitaxy. The wavelength shift is due to a lateral thickness variation in the Al(0.2)Ga(0.8)As cavity, which is induced by a substrate temperature profile during growth. A 20 nm shift in lasing wavelength is obtained in a VCSEL array.

Impedance self-matching ultra-narrow linewidth fiber resonator by use of a tunable π-phase-shifted FBG.

PubMed

Jing, Mingyong; Yu, Bo; Hu, Jianyong; Hou, Huifang; Zhang, Guofeng; Xiao, Liantuan; Jia, Suotang

2017-05-15

In this paper, we present a novel ultra-narrow linewidth fiber resonator formed by a tunable polarization maintaining (PM) π-phase-shifted fiber Bragg grating and a PM uniform fiber Bragg grating with a certain length of PM single mode fiber patch cable between them. Theoretical prediction shows that this resonator has ultra-narrow linewidth resonant peaks and is easy to realize impedance matching. We experimentally obtain 3 MHz narrow linewidth impedance matched resonant peak in a 7.3 m ultra-long passive fiber cavity. The impedance self-matching characteristic of this resonator also makes itself particularly suitable for use in ultra-sensitive sensors, ultra-narrow band rejection optical filters and fiber lasers applications.

Geometrical optics model of Mie resonances

PubMed

Roll; Schweiger

2000-07-01

The geometrical optics model of Mie resonances is presented. The ray path geometry is given and the resonance condition is discussed with special emphasis on the phase shift that the rays undergo at the surface of the dielectric sphere. On the basis of this model, approximate expressions for the positions of first-order resonances are given. Formulas for the cavity mode spacing are rederived in a simple manner. It is shown that the resonance linewidth can be calculated regarding the cavity losses. Formulas for the mode density of Mie resonances are given that account for the different width of resonances and thus may be adapted to specific experimental situations.

Numerical modeling of Stokes flows over a superhydrophobic surface containing gas bubbles

NASA Astrophysics Data System (ADS)

Ageev, A. I.; Golubkina, I. V.; Osiptsov, A. N.

2017-10-01

This paper continues the numerical modeling of Stokes flows near cavities of a superhydrophobic surface, occupied by gas bubbles, based on the Boundary Element Method (BEM). The aim of the present study is to estimate the friction reduction (pressure drop) in a microchannel with a bottom superhydrophobic surface, the texture of which is formed by a periodic system of striped rectangular microcavities containing compressible gas bubbles. The model proposed takes into account the streamwise variation of the bubble shift into the cavities, caused by the longitudinal pressure gradient in the channel flow. The solution for the macroscopic (averaged) flow in the microchannel, constructed using an effective slip boundary condition on the superhydrophobic bottom wall, is matched with the solution of the Stokes problem at the microscale of a single cavity containing a gas bubble. The 2D Stokes problems of fluid flow over single cavities containing curved phase interfaces with the condition of zero shear stress are reduced to the boundary integral equations which are solved using the BEM method.

Cavity-Enhanced Raman Spectroscopy of Natural Gas with Optical Feedback cw-Diode Lasers.

PubMed

Hippler, Michael

2015-08-04

We report on improvements made on our previously introduced technique of cavity-enhanced Raman spectroscopy (CERS) with optical feedback cw-diode lasers in the gas phase, including a new mode-matching procedure which keeps the laser in resonance with the optical cavity without inducing long-term frequency shifts of the laser, and using a new CCD camera with improved noise performance. With 10 mW of 636.2 nm diode laser excitation and 30 s integration time, cavity enhancement achieves noise-equivalent detection limits below 1 mbar at 1 bar total pressure, depending on Raman cross sections. Detection limits can be easily improved using higher power diodes. We further demonstrate a relevant analytical application of CERS, the multicomponent analysis of natural gas samples. Several spectroscopic features have been identified and characterized. CERS with low power diode lasers is suitable for online monitoring of natural gas mixtures with sensitivity and spectroscopic selectivity, including monitoring H2, H2S, N2, CO2, and alkanes.

Goos-Hänchen shifts of partially coherent light beams from a cavity with a four-level Raman gain medium

NASA Astrophysics Data System (ADS)

Ziauddin; Lee, Ray-Kuang; Qamar, Sajid

2016-09-01

We theoretically investigate spatial and angular Goos-Hänchen (GH) shifts (both negative and positive) in the reflected light for a partial coherent light incident on a cavity. A four-level Raman gain atomic medium is considered in a cavity. The effects of spatial coherence, beam width, and mode index of partial coherent light fields on spatial and angular GH shifts are studied. Our results reveal that a large magnitude of negative and positive GH shifts in the reflected light is achievable with the introduction of partial coherent light fields. Furthermore, the amplitude of spatial (negative and positive) GH shifts are sharply affected by the partial coherent light beam as compared to angular (negative and positive) GH shifts in the reflected light.

Fast ferroelectric phase shifters for energy recovery linacs

DOE PAGES

Kazakov, S. Yu; Shchelkunov, S. V.; Yakovlev, V. P.; ...

2010-11-24

Fast phase shifters are described that use a novel barium strontium titanate ceramic that can rapidly change its dielectric constant as an external bias voltage is changed. These phase shifters promise to reduce by ~10 times the power requirements for the rf source needed to drive an energy recovery linac (ERL). Such phase shifters will be coupled with superconducting radiofrequency cavities so as to tune them to compensate for phase instabilities, whether beam-driven or those caused by microphonics. The most promising design is presented, which was successfully cold tested and demonstrated a switching speed of ~30 ns for 77 deg, correspondingmore » to < 0.5 ns per deg of rf phase. As a result, other crucial issues (losses, phase shift values, etc.) are discussed.« less

Homodyne locking of a squeezer.

PubMed

Heurs, M; Petersen, I R; James, M R; Huntington, E H

2009-08-15

We report on the successful implementation of an approach to locking the frequencies of an optical parametric oscillator (OPO)-based squeezed-vacuum source and its driving laser. The technique allows the simultaneous measurement of the phase shifts induced by a cavity, which may be used for the purposes of frequency locking, as well as the simultaneous measurement of the sub-quantum-noise-limited (sub-QNL) phase quadrature output of the OPO. The homodyne locking technique is cheap, easy to implement, and has the distinct advantage that subsequent homodyne measurements are automatically phase locked. The homodyne locking technique is also unique in that it is a sub-QNL frequency discriminator.

Theory of Talbot lasers

NASA Astrophysics Data System (ADS)

Guillet de Chatellus, H.; Lacot, E.; Glastre, W.; Jacquin, O.; Hugon, O.

2013-09-01

We provide a theoretical study of frequency-shifted feedback (FSF) lasers, i.e., lasers with an internal frequency shifter, seeded with a monochromatic wave. The resulting spectrum consists in a set of equidistant modes, labeled by n, whose phases vary quadratically with n. We prove the emergence of a temporal fractional Talbot effect, leading to generation of Fourier-transform-limited pulses at a repetition rate tunable by the parameters of the FSF cavity (cavity length and frequency shift per round trip), and limited by the spectral bandwidth of the laser. We characterize in detail the output field of this so-called “Talbot laser” and emphasize its specific intensity fluctuations. We evidence connections with some aspects of number theory by the appearance of Gauss sums and theta series in the expression of the laser field. Our predictions are in full agreement with the experimental results published in Guillet de Chatellus [Opt. ExpressOPEXFF1094-408710.1364/OE.21.015065 21, 15065 (2013)]. Practical applications and limitations are discussed.

Rotation Sensing with Trapped Ions

DTIC Science & Technology

2016-09-01

Sagnac effect can be used to measure the rotational velocity Ω of a reference frame by observing the phase shift of an interferometer in that frame whose...sensitivity of interferometric gyroscopes. For photons, optical fibers (or ring laser cavities) allow many effective round-trips through the Sagnac...interferometer, thereby increasing the effective area A by 2 times the number of round trips (M) without increasing the actual area of the apparatus. This

Combined dispersive/interference spectroscopy for producing a vector spectrum

DOEpatents

Erskine, David J.

2002-01-01

A method of measuring the spectral properties of broadband waves that combines interferometry with a wavelength disperser having many spectral channels to produce a fringing spectrum. Spectral mapping, Doppler shifts, metrology of angles, distances and secondary effects such as temperature, pressure, and acceleration which change an interferometer cavity length can be measured accurately by a compact instrument using broadband illumination. Broadband illumination avoids the fringe skip ambiguities of monochromatic waves. The interferometer provides arbitrarily high spectral resolution, simple instrument response, compactness, low cost, high field of view and high efficiency. The inclusion of a disperser increases fringe visibility and signal to noise ratio over an interferometer used alone for broadband waves. The fringing spectrum is represented as a wavelength dependent 2-d vector, which describes the fringe amplitude and phase. Vector mathematics such as generalized dot products rapidly computes average broadband phase shifts to high accuracy. A Moire effect between the interferometer's sinusoidal transmission and the illumination heterodynes high resolution spectral detail to low spectral detail, allowing the use of a low resolution disperser. Multiple parallel interferometer cavities of fixed delay allow the instantaneous mapping of a spectrum, with an instrument more compact for the same spectral resolution than a conventional dispersive spectrometer, and not requiring a scanning delay.

Intravital hybrid optical-optoacoustic microscopy based on fiber-Bragg interferometry

NASA Astrophysics Data System (ADS)

Shnaiderman, Rami; Wissmeyer, Georg; Seeger, Markus; Estrada, Hector; Ntziachristos, Vasilis

2018-02-01

Optoacoustic microscopy (OAM) has enabled high-resolution, label-free imaging of tissues at depths not achievable with purely optical microscopy. However, widespread implementation of OAM into existing epi-illumination microscopy setups is often constrained by the performance and size of the commonly used piezoelectric ultrasound detectors. In this work, we introduce a novel acoustic detector based on a π-phase-shifted fiber Bragg grating (π-FBG) interferometer embedded inside an ellipsoidal acoustic cavity. The cavity enables seamless integration of epi-illumination OAM into existing microscopy setups by decoupling the acoustic and optical paths between the microscope objective and the sample. The cavity also acts as an acoustic condenser, boosting the sensitivity of the π-FBG and enabling cost effective CW-laser interrogation technique. We characterize the sensor's sensitivity and bandwidth and demonstrate hybrid OAM and second-harmonic imaging of phantoms and mouse tissue in vivo.

Interaction of a parabolic-shaped pulse pair in a passively mode-locked Yb-doped fiber laser

NASA Astrophysics Data System (ADS)

Wang, Da-Shuai; Wu, Ge; Gao, Bo; Tian, Xiao-Jian

2013-01-01

We numerically investigate the formation and interaction of a parabolic-shaped pulse pair in a passively mode-locked Yb-doped fiber laser. Based on a lumped model, the parabolic-shaped pulse pair is obtained by controlling the inter-cavity average dispersion and gain saturation energy, Moreover, pulse repulsive and attractive motion are also achieved with different pulse separations. Simulation results show that the phase shift plays an important role in pulse interaction, and the interaction is determined by the inter-cavity average dispersion and gain saturation energy, i.e., the strength of the interaction is proportional to the gain saturation energy, a stronger gain saturation energy will result in a higher interaction intensity. On the contrary, the increase of the inter-cavity dispersion will counterbalance some interaction force. The results also show that the interaction of a parabolic-shaped pulse pair has a larger interaction distance compared to conventional solitons.

Geometrically tunable Fabry-Perot filters based on reflection phase shift of high contrast gratings

NASA Astrophysics Data System (ADS)

Fang, Liang; Shi, Zhendong; Cheng, Xin; Peng, Xiang; Zhang, Hui

2016-03-01

We propose tunable Fabry-Perot filters constituted by double high contrast gratings (HCGs) arrays with different periods acting as reflectors separated by a fixed short cavity, based on high reflectivity and the variety reflection phase shift of HCG array which realize dynamic regulation of the filtering condition. Single optimized HCG obtains the reflectivity of higher than 99% in a grating period ranging from 0.68μm to 0.8μm across a bandwidth of 30nm near the 1.55μm wavelength. The filters can achieve the full width at half maximum (FWHM) of spectral line of less than 0.15nm, and the linear relationship of peak wavelengths and grating periods is established. The simulation results indicate a potential new approach to design a tunable narrowband transmission filter.

Spectral tuning of optical coupling between air-mode nanobeam cavities and individual carbon nanotubes

NASA Astrophysics Data System (ADS)

Machiya, Hidenori; Uda, Takushi; Ishii, Akihiro; Kato, Yuichiro K.

Air-mode nanobeam cavities allow for high efficiency coupling to air-suspended carbon nanotubes due to their unique mode profile that has large electric fields in air. Here we utilize heating-induced energy shift of carbon nanotube emission to investigate the cavity quantum electrodynamics effects. In particular, we use laser-induced heating which causes a large blue-shift of the nanotube photoluminescence as the excitation power is increased. Combined with a slight red-shift of the cavity mode at high powers, detuning of nanotube emission from the cavity can be controlled. We estimate the spontaneous emission coupling factor β at different spectral overlaps and find an increase of β factor at small detunings, which is consistent with Purcell enhancement of nanotube emission. Work supported by JSPS (KAKENHI JP26610080, JP16K13613), Asahi Glass Foundation, Canon Foundation, and MEXT (Photon Frontier Network Program, Nanotechnology Platform).

Modeling and Optimization of Optical Half Adder in Two Dimensional Photonic Crystals

NASA Astrophysics Data System (ADS)

Sonth, Mahesh V.; Soma, Savita; Gowre, Sanjaykumar C.; Biradar, Nagashettappa

2018-05-01

The output of photonic integrated devices is enhanced using crystal waveguides and cavities but optimization of these devices is a topic of research. In this paper, optimization of the optical half adder in two-dimensional (2-D) linear photonic crystals using four symmetric T-shaped waveguides with 180° phase shift inputs is proposed. The input section of a T-waveguide acts as a beam splitter, and the output section acts as a power combiner. The constructive and destructive interference phenomenon will provide an output optical power. Output port Cout will receive in-phase power through the 180° phase shifter cavity designed near the junction. The optical half adder is modeled in a 2-D photonic crystal using the finite difference time domain method (FDTD). It consists of a cubic lattice with an array of 39 × 43 silicon rods of radius r 0.12 μm and 0.6 μm lattice constant a. The extinction ratio r e of 11.67 dB and 12.51 dB are achieved at output ports using the RSoft FullWAVE-6.1 software package.

Optical resonators for true-time-delay beam steering

NASA Astrophysics Data System (ADS)

Gesell, Leslie H.; Evanko, Stephen M.

1996-06-01

Conventional true time delay beamforming and steering devices rely on switching between various lengths of delay line. Therefore only discrete delays are possible. Proposed is a new photonics concept for true time delay beamforming which provides a finely controlled continuum of delays with switching speeds on the order of 10's of nanoseconds or faster. The architecture uses an array of waveguide cavities with different resonate frequencies to channelize the signal. Each spectral component of the signal is phase shifted by an amount proportional to the frequency of that component and the desired time delay. These phase shifted spectral components are then summed to obtain the delayed signal. This paper provides an overview of the results of a Phase I SBIR contract where this concept has been refined and analyzed. The parameters for an operational system are determined and indication of the feasibility of this approach is given. Among the issues addressed are the requirements of the resonators and the methods necessary to implement fiber optic Bragg gratings as these resonators.

Laser frequency stabilization and shifting by using modulation transfer spectroscopy

NASA Astrophysics Data System (ADS)

Cheng, Bing; Wang, Zhao-Ying; Wu, Bin; Xu, Ao-Peng; Wang, Qi-Yu; Xu, Yun-Fei; Lin, Qiang

2014-10-01

The stabilizing and shifting of laser frequency are very important for the interaction between the laser and atoms. The modulation transfer spectroscopy for the 87Rb atom with D2 line transition F = 2 → F' = 3 is used for stabilizing and shifting the frequency of the external cavity grating feedback diode laser. The resonant phase modulator with electro—optical effect is used to generate frequency sideband to lock the laser frequency. In the locking scheme, circularly polarized pump- and probe-beams are used. By optimizing the temperature of the vapor, the pump- and probe-beam intensity, the laser linewidth of 280 kHz is obtained. Furthermore, the magnetic field generated by a solenoid is added into the system. Therefore the system can achieve the frequency locking at any point in a range of hundreds of megahertz frequency shifting with very low power loss.

Damping of quasiparticles in a Bose-Einstein condensate coupled to an optical cavity

NASA Astrophysics Data System (ADS)

Kónya, G.; Szirmai, G.; Domokos, P.

2014-07-01

We present a general theory for calculating the damping rate of elementary density-wave excitations in a Bose-Einstein condensate strongly coupled to a single radiation field mode of an optical cavity. Thereby we give a detailed derivation of the huge resonant enhancement in the Beliaev damping of a density-wave mode, predicted recently by Kónya et al. [Phys. Rev. A 89, 051601(R) (2014), 10.1103/PhysRevA.89.051601]. The given density-wave mode constitutes the polaritonlike soft mode of the self-organization phase transition. The resonant enhancement takes place, in both the normal and the ordered phases, outside the critical region. We show that the large damping rate is accompanied by a significant frequency shift of this polariton mode. Going beyond the Born-Markov approximation and determining the poles of the retarded Green's function of the polariton, we reveal a strong coupling between the polariton and a collective mode in the phonon bath formed by the other density-wave modes.

Accuracy evaluation of the LPTF optically pumped primary frequency standard

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

De Clercq, E.; Rovera, G.D.; Clairon, A.

1994-12-31

The optically pumped Cesium beam frequency standard under development in our laboratory was first evaluated in `93. The short term stability was {sigma}{sub y}({tau}) is 5.5 x 10{sup -13}, {tau}{sup -1/2}. The accuracy has been estimated to 1.1 x 10{sup -13}, mainly limited by the distributed phase shift. After modification of the cavity, a new evaluation is in progress and will be presented at the conference.

In-phased second harmonic wave array generation with intra-Talbot-cavity frequency-doubling.

PubMed

Hirosawa, Kenichi; Shohda, Fumio; Yanagisawa, Takayuki; Kannari, Fumihiko

2015-03-23

The Talbot cavity is one promising method to synchronize the phase of a laser array. However, it does not achieve the lowest array mode with the same phase but the highest array mode with the anti-phase between every two adjacent lasers, which is called out-phase locking. Consequently, their far-field images exhibit 2-peak profiles. We propose intra-Talbot-cavity frequency-doubling. By placing a nonlinear crystal in a Talbot cavity, the Talbot cavity generates an out-phased fundamental wave array, which is converted into an in-phase-locked second harmonic wave array at the nonlinear crystal. We demonstrate numerical calculations and experiments on intra-Talbot-cavity frequency-doubling and obtain an in-phase-locked second harmonic wave array for a Nd:YVO₄ array laser.

Analysis and design of tunable wideband microwave photonics phase shifter based on Fabry-Perot cavity and Bragg mirrors in silicon-on-insulator waveguide.

PubMed

Qu, Pengfei; Zhou, Jingran; Chen, Weiyou; Li, Fumin; Li, Haibin; Liu, Caixia; Ruan, Shengping; Dong, Wei

2010-04-20

We designed a microwave (MW) photonics phase shifter, consisting of a Fabry-Perot filter, a phase modulation region (PMR), and distributed Bragg reflectors, in a silicon-on-insulator rib waveguide. The thermo-optics effect was employed to tune the PMR. It was theoretically demonstrated that the linear MW phase shift of 0-2pi could be achieved by a refractive index variation of 0-9.68x10(-3) in an ultrawideband (about 38?GHz-1.9?THz), and the corresponding tuning resolution was about 6.92 degrees / degrees C. The device had a very compact size. It could be easily integrated in silicon optoelectronic chips and expected to be widely used in the high-frequency MW photonics field.

Detection of nitrogen dioxide by CW cavity-enhanced spectroscopy

NASA Astrophysics Data System (ADS)

Jie, Guo; Han, Ye-Xing; Yu, Zhi-Wei; Tang, Huai-Wu

2016-11-01

In the paper, an accurate and sensitive system was used to monitor the ambient atmospheric NO2 concentrations. This system utilizes cavity attenuated phase shift spectroscopy(CAPS), a technology related to cavity ring down spectroscopy(CRDS). Advantages of the CAPS system include such as: (1) cheap and easy to control the light source, (2) high accuracy, and (3) low detection limit. The performance of the CAPS system was evaluated by measuring of the stability and response of the system. The minima ( 0.08 ppb NO2) in the Allan plots show the optimum average time( 100s) for optimum detection performance of the CAPS system. Over a 20-day-long period of the ambient atmospheric NO2 concentrations monitoring, a comparison of the CAPS system with an extremely accurate and precise chemiluminescence-based NOx analyzer showed that the CAPS system was able to reliably and quantitatively measure both large and small fluctuations in the ambient nitrogen dioxide concentration. The experimental results show that the measuring instrument results correlation is 0.95.

Temporal shaping of quantum states released from a superconducting cavity memory

NASA Astrophysics Data System (ADS)

Burkhart, L.; Axline, C.; Pfaff, W.; Zou, C.; Zhang, M.; Narla, A.; Frunzio, L.; Devoret, M. H.; Jiang, L.; Schoelkopf, R. J.

State transfer and entanglement distribution are essential primitives in network-based quantum information processing. We have previously demonstrated an interface between a quantum memory and propagating light fields in the microwave domain: by parametric conversion in a single Josephson junction, we have coherently released quantum states from a superconducting cavity resonator into a transmission line. Protocols for state transfer mediated by propagating fields typically rely on temporal mode-matching of couplings at both sender and receiver. However, parametric driving on a single junction results in dynamic frequency shifts, raising the question of whether the pumps alone provide enough control for achieving this mode-matching. We show, in theory and experiment, that phase and amplitude shaping of the parametric drives allows arbitrary control over the propagating field, limited only by the drives bandwidth and amplitude constraints. This temporal mode shaping technique allows for release and capture of quantum states, providing a credible route towards state transfer and entanglement generation in quantum networks in which quantum states are stored and processed in cavities.

An optical biosensor using MEMS-based V-grooves

NASA Astrophysics Data System (ADS)

Tian, Ye; Ma, Xiaodong; Zou, Xiaotian; Wu, Nan; Wang, Xingwei

2011-05-01

An optical fiber biosensor featuring miniaturization, electromagnetic interference (EMI)-immunity, and flexibility is presented. The sensor was fabricated by aligning two gold-deposited optical single-mode fiber facets inside V-grooves on a silicon chip to form a Fabry-Perot (FP) cavity. The mirrors on the fiber facets were made of deposited gold (Au) films, which provided a high finesse to produce a highly sensitivity. Microelectromechanical systems (MEMS) fabrication techniques were used to precisely control the profile and angle of the V-grooves on the silicon. The biotin-terminated thiol molecule was firstly immobilized on the gold surface. Subsequently, the molecules of Neutravidin were specifically bound to the biotin-terminated self-assembled monolayers (SAMs). The induced changes of cavity length and refractive index (RI) upon the gold surface lead to an optical path difference (OPD) of the FP cavity, which was detected by demodulating the transmission spectrum phase shift. By taking advantage of MEMS techniques, multiple biosensors can be integrated into one small silicon chip for detecting various biomolecule targets simultaneously.

Mass sensing based on a circuit cavity electromechanical system

NASA Astrophysics Data System (ADS)

Jiang, Cheng; Chen, Bin; Li, Jin-Jin; Zhu, Ka-Di

2011-10-01

We present a scheme for mass sensing based on a circuit cavity electromechanical system where a free-standing, flexible aluminium membrane is capacitively coupled to a superconducting microwave cavity. Integration with the microwave cavity enables capacitive readout of the mechanical resonance directly on the chip. A microwave pump field and a second probe field are simultaneously applied to the cavity. The accreted mass landing on the membrane can be measured conveniently by tracking the mechanical resonance frequency shifts due to mass changes in the probe transmission spectrum. The mass responsivity for the membrane is 0.72 Hz/ag and we demonstrate that frequency shifts induced by adsorption of one hundred 1587 bp DNA molecules can be well resolved in the probe transmission spectrum.

Compact MEMS external cavity tunable laser with ultra-narrow linewidth for coherent detection.

PubMed

Zhang, Di; Zhao, Jianyi; Yang, Qi; Liu, Wen; Fu, Yanfeng; Li, Chao; Luo, Ming; Hu, Shenglei; Hu, Qianggao; Wang, Lei

2012-08-27

A compact and ultra-narrow linewidth tunable laser with an external cavity based on a simple single-axis-MEMS mirror is presented in this paper. We discuss the simulation of this tunable laser using a two-step hybrid analysis method to obtain an optimal design of the device. A wide wavelength tuning range about 40 nm in C-band with a narrow linewidth of less than 50 kHz and wavelength accuracy of ± 1 GHz over the entire tuning range can be achieved experimentally. We also conduct several experiments under different conditions to test the tunable laser. This device shows an excellent performance in both single-carrier polarization-multiplexed quadrature phase-shift keying (PM-QPSK) and multi-carrier orthogonal frequency division multiplexing (OFDM) coherent systems.

High precision slotted cavity measurement of a novel ceramic state polymer electrolyte

NASA Astrophysics Data System (ADS)

Quan, Wei; NurulAfsar, Mohammed

2018-01-01

Thin film materials are already used in a variety of microwave and higher frequency applications such as electrically tunable microwave devices, integrated circuits like MMICs, radomes, and radar absorbing coating. The determination of the dielectric properties of these films is thus of significant importance. The measurement of complex dielectric permittivity of thin films is very difficult at microwave, millimeter, and THz frequencies because both the amplitude change and phase shift are not large enough to evaluate the real part of the dielectric permittivity. A specially designed transverse slotted cavity for X-band microwave measurement has been designed and constructed to employ with a vector network analyzer to evaluate the real part of dielectric permittivity of thin films accurately and conveniently. Commercially available polymer thin films are measured to validate the methods.

Electronic confining effects in Sierpiński triangle fractals

NASA Astrophysics Data System (ADS)

Wang, Hao; Zhang, Xue; Jiang, Zhuoling; Wang, Yongfeng; Hou, Shimin

2018-03-01

Electron confinement in fractal Sierpiński triangles (STs) on Ag(111) is investigated using scanning tunneling spectroscopy and theoretically simulated by employing an improved two-dimensional (2D) multiple scattering theory in which the energy-dependent phase shifts are explicitly calculated from the electrostatic potentials of the molecular building block of STs. Well-defined bound surface states are observed in three kinds of triangular cavities with their sides changing at a scale factor of 2. The decrease in length of the cavities results in an upshift of the resonances that deviates from an expected inverse quadratic dependence on the cavity length due to the less efficient confinement of smaller triangular cavities. Differential conductance maps at some specific biases present a series of alternative bright and dark rounded triangles preserving the symmetry of the boundary. Our improved 2D multiple scattering model reproduces the characteristics of the standing wave patterns and all features in the differential conductance spectra measured in experiments, illustrating that the elastic loss boundary scattering dominates the resonance broadening in these ST quantum corrals. Moreover, the self-similar structure of STs, that a larger central cavity is surrounded by three smaller ones with a half side length, gives rise to interactions of surface states confined in neighboring cavities, which are helpful for the suppression of the linewidth in differential conductance spectra.

United States Air Force Weapons Laboratory Research Scholar Program, 1983-1984.

DTIC Science & Technology

1984-10-01

voltage upon passing through an RC circuit .) The phase shift is given by = tan-Tf (3) * where T is the cavity lifetime and f is the modulation ...spark in air at the external terminals of a filter module has * S. . . . . .. S ** . * * * * Page 8-18 approximately the same effect on the circuit as a... module usually contains a metal oxide varistor(s), and perhaps also 3 an RFI filter circuit . We shall discuss line conditioners and surge protection

Weighted least-square approach for simultaneous measurement of multiple reflective surfaces

NASA Astrophysics Data System (ADS)

Tang, Shouhong; Bills, Richard E.; Freischlad, Klaus

2007-09-01

Phase shifting interferometry (PSI) is a highly accurate method for measuring the nanometer-scale relative surface height of a semi-reflective test surface. PSI is effectively used in conjunction with Fizeau interferometers for optical testing, hard disk inspection, and semiconductor wafer flatness. However, commonly-used PSI algorithms are unable to produce an accurate phase measurement if more than one reflective surface is present in the Fizeau interferometer test cavity. Examples of test parts that fall into this category include lithography mask blanks and their protective pellicles, and plane parallel optical beam splitters. The plane parallel surfaces of these parts generate multiple interferograms that are superimposed in the recording plane of the Fizeau interferometer. When using wavelength shifting in PSI the phase shifting speed of each interferogram is proportional to the optical path difference (OPD) between the two reflective surfaces. The proposed method is able to differentiate each underlying interferogram from each other in an optimal manner. In this paper, we present a method for simultaneously measuring the multiple test surfaces of all underlying interferograms from these superimposed interferograms through the use of a weighted least-square fitting technique. The theoretical analysis of weighted least-square technique and the measurement results will be described in this paper.

Dipole-dipole interaction in cavity QED: The weak-coupling, nondegenerate regime

NASA Astrophysics Data System (ADS)

Donaire, M.; Muñoz-Castañeda, J. M.; Nieto, L. M.

2017-10-01

We compute the energies of the interaction between two atoms placed in the middle of a perfectly reflecting planar cavity, in the weak-coupling nondegenerate regime. Both inhibition and enhancement of the interactions can be obtained by varying the size of the cavity. We derive exact expressions for the dyadic Green's function of the cavity field which mediates the interactions and apply time-dependent quantum perturbation theory in the adiabatic approximation. We provide explicit expressions for the van der Waals potentials of two polarizable atomic dipoles and the electrostatic potential of two induced dipoles. We compute the van der Waals potentials in three different scenarios: two atoms in their ground states, two atoms excited, and two dissimilar atoms with one of them excited. In addition, we calculate the phase-shift rate of the two-atom wave function in each case. The effect of the two-dimensional confinement of the electromagnetic field on the dipole-dipole interactions is analyzed. This effect depends on the atomic polarization. For dipole moments oriented parallel to the cavity plates, both the electrostatic and the van der Waals interactions are exponentially suppressed for values of the cavity width much less than the interatomic distance, whereas for values of the width close to the interatomic distance, the strength of both interactions is higher than their values in the absence of cavity. For dipole moments perpendicular to the plates, the strength of the van der Waals interaction decreases for values of the cavity width close to the interatomic distance, while it increases for values of the width much less than the interatomic distance with respect to its strength in the absence of cavity. We illustrate these effects by computing the dipole-dipole interactions between two alkali atoms in circular Rydberg states.

Ultrafast control of strong light-matter coupling

NASA Astrophysics Data System (ADS)

Lange, Christoph; Cancellieri, Emiliano; Panna, Dmitry; Whittaker, David M.; Steger, Mark; Snoke, David W.; Pfeiffer, Loren N.; West, Kenneth W.; Hayat, Alex

2018-01-01

We dynamically modulate strong light-matter coupling in a GaAs/AlGaAs microcavity using intense ultrashort laser pulses tuned below the interband exciton energy, which induce a transient Stark shift of the cavity polaritons. For 225-fs pulses, shorter than the cavity Rabi cycle period of 1000 fs, this shift decouples excitons and cavity photons for the duration of the pulse, interrupting the periodic energy exchange between photonic and electronic states. For 1500-fs pulses, longer than the Rabi cycle period, however, the Stark shift does not affect the strong coupling. The two regimes are marked by distinctly different line shapes in ultrafast reflectivity measurements—regardless of the Stark field intensity. The crossover marks the transition from adiabatic to diabatic switching of strong light-matter coupling.

Collective Lamb Shift of a Nanoscale Atomic Vapor Layer within a Sapphire Cavity

NASA Astrophysics Data System (ADS)

Peyrot, T.; Sortais, Y. R. P.; Browaeys, A.; Sargsyan, A.; Sarkisyan, D.; Keaveney, J.; Hughes, I. G.; Adams, C. S.

2018-06-01

We measure the near-resonant transmission of light through a dense medium of potassium vapor confined in a cell with nanometer thickness in order to investigate the origin and validity of the collective Lamb shift. A complete model including the multiple reflections in the nanocell reproduces accurately the observed line shape. It allows the extraction of a density-dependent shift and width of the bulk atomic medium resonance, deconvolved from the cavity effect. We observe an additional, unexpected dependence of the shift with the thickness of the medium. This extra dependence demands further experimental and theoretical investigations.

Detecting Axion Dark Matter with Superconducting Qubits

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

Dixit, Akash; Chou, Aaron; Schuster, David

Axion dark matter haloscopes aim to detect dark matter axions converting to single photons in resonant cavities bathed in a uniform magnetic field. A qubit (two level system) operating as a single microwave photon detector is a viable readout system for such detectors and may offer advantages over the quantum limited amplifiers currently used. When weakly coupled to the detection cavity, the qubit transition frequency is shifted by an amount proportional to the cavity photon number. Through spectroscopy of the qubit, the frequency shift is measured and the cavity occupation number is extracted. At low enough temperatures, this would allowmore » sensitivities exceeding that of the standard quantum limit.« less

Thermal dissociation cavity attenuated phase shift spectroscopy for continuous measurement of total peroxy and organic nitrates in the clean atmosphere

NASA Astrophysics Data System (ADS)

Sadanaga, Yasuhiro; Takaji, Ryo; Ishiyama, Ayana; Nakajima, Kazuo; Matsuki, Atsushi; Bandow, Hiroshi

2016-07-01

A thermal dissociation cavity attenuated phase shift spectroscopy (TD-CAPS) instrument was developed for measuring total peroxy nitrates (PNs) and organic nitrates (ONs) concentrations in the clean atmosphere. This instrument is easy to operate and can be applied to continuous measurement of PNs and ONs. A continuously measurable system is convenient to perform observations, especially in remote areas. Three lines (NO2, PNs, and ONs lines) were used for thermal dissociation. The NO2 line contains a quartz tube that is not heated, while the PN and ON lines contain quartz tubes that are heated at 433 K and 633 K, respectively. The concentrations of NO2, NO2 + PNs, and NO2 + PNs + ONs can be obtained from the NO2, PN, and ON lines, respectively. The lower limit values of the detection limit (3σ) for PNs and ONs were estimated to be 21 parts per trillion by volume with an integration time of 2 min. PNs were selectively thermally decomposed in the PNs line and formed NO2 quantitatively. In the ONs line, both PNs and ONs were thermally decomposed to produce NO2 quantitatively, but partial decomposition of HNO3 at 633 K interfered with the ONs measurement. Therefore, a HNO3 scrubber is required before the ONs line. Continuous observations were conducted with the TD-CAPS instrument in a remote area, and the instrument performed well for obtaining PNs and ONs concentrations.

Study of the effective point of measurement for ion chambers in electron beams by Monte Carlo simulation

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

Wang, L. L. W.; Rogers, D. W. O.

In current dosimetry protocols for electron beams, for plane-parallel chambers, the effective point of measurement is at the front face of the cavity, and, for cylindrical chambers, it is at a point shifted 0.5r upstream from the cavity center. In this study, Monte Carlo simulations are employed to study the issue of effective point of measurement for both plane-parallel chambers and cylindrical thimble chambers in electron beams. It is found that there are two ways of determining the position of the effective point of measurement: One is to match the calculated depth-ionization curve obtained from a modeled chamber to amore » calculated depth-dose curve; the other is to match the electron fluence spectrum in the chamber cavity to that in the phantom. For plane-parallel chambers, the effective point of measurement determined by the first method is generally not at the front face of the chamber cavity, which is obtained by the second method, but shifted downstream toward the cavity center by an amount that could be larger than one-half a millimeter. This should not be ignored when measuring depth-dose curves in electron beams. For cylindrical chambers, these two methods also give different positions of the effective point of measurement: The first gives a shift of 0.5r, which is in agreement with measurements for high-energy beams and is the same as the value currently used in major dosimetry protocols; the latter gives a shift of 0.8r, which is closer to the value predicted by a theoretical calculation assuming no-scatter conditions. The results also show that the shift of 0.8r is more appropriate if the cylindrical chamber is to be considered as a Spencer-Attix cavity. In electron beams, since the water/air stopping-power ratio changes with depth in a water phantom, the difference of the two shifts (0.3r) will lead to an incorrect evaluation of the water/air stopping-power ratio at the point of measurement, thus resulting in a systematic error in determining the absorbed dose by cylindrical chambers. It is suggested that a shift of 0.8r be used for electron beam calibrations with cylindrical chambers and a shift of 0.4r-0.5r be used for depth-dose measurements.« less

Study of the effective point of measurement for ion chambers in electron beams by Monte Carlo simulation.

PubMed

Wang, L L W; Rogers, D W O

2009-06-01

In current dosimetry protocols for electron beams, for plane-parallel chambers, the effective point of measurement is at the front face of the cavity, and, for cylindrical chambers, it is at a point shifted 0.5r upstream from the cavity center. In this study, Monte Carlo simulations are employed to study the issue of effective point of measurement for both plane-parallel chambers and cylindrical thimble chambers in electron beams. It is found that there are two ways of determining the position of the effective point of measurement: One is to match the calculated depth-ionization curve obtained from a modeled chamber to a calculated depth-dose curve; the other is to match the electron fluence spectrum in the chamber cavity to that in the phantom. For plane-parallel chambers, the effective point of measurement determined by the first method is generally not at the front face of the chamber cavity, which is obtained by the second method, but shifted downstream toward the cavity center by an amount that could be larger than one-half a millimeter. This should not be ignored when measuring depth-dose curves in electron beams. For cylindrical chambers, these two methods also give different positions of the effective point of measurement: The first gives a shift of 0.5r, which is in agreement with measurements for high-energy beams and is the same as the value currently used in major dosimetry protocols; the latter gives a shift of 0.8r, which is closer to the value predicted by a theoretical calculation assuming no-scatter conditions. The results also show that the shift of 0.8r is more appropriate if the cylindrical chamber is to be considered as a Spencer-Attix cavity. In electron beams, since the water/air stopping-power ratio changes with depth in a water phantom, the difference of the two shifts (0.3r) will lead to an incorrect evaluation of the water/air stopping-power ratio at the point of measurement, thus resulting in a systematic error in determining the absorbed dose by cylindrical chambers. It is suggested that a shift of 0.8r be used for electron beam calibrations with cylindrical chambers and a shift of 0.4r-0.5r be used for depth-dose measurements.

Mass sensor based on split-nanobeam optomechanical oscillator

NASA Astrophysics Data System (ADS)

Zhang, Yeping; Ai, Jie; Xiang, Yanjun; He, Qinghua; Li, Tao; Ma, Jingfang

2016-03-01

Mass sensing based on monitoring the frequency shifts induced by added mass in oscillators is a well-known and widely used technique. The optomechanical crystal cavity has strong interaction between optical mode and mechanical mode. Radiation pressure driven optomechanical crystal cavity are excellent candidates for mass detection due to their simplicity, sensitivity and all optical operation. In an optomechanical crystal cavity, a high quality factor optical mode simultaneously serves as an efficient actuator and a sensitive probe for precise monitoring the mechanical frequency change of the cavity structure. Here, a split-nanobeam optomechanical crystal cavity is proposed, the sensing resolution as small as 0.33ag (1ag=10-21kg) and the frequency shift is more than 30MHz. This is important and promising for achieve ultimate-precision mass sensing including proteins and other molecules.

Assessment by Monte Carlo computer simulations of the phase behavior of hard spherocylinders confined within cylindrical cavities.

PubMed

Viveros-Méndez, Perla X; Gil-Villegas, Alejandro; Aranda Espinoza, Said

2017-12-21

The phase behavior of hard spherocylinders (HSCs) confined in cylindrical cavities is studied using Monte Carlo simulations in the canonical ensemble. Results are presented for different values of the particles' aspect ratio l/σ, where l and σ are the length and diameter of the cylinder and hemispherical caps, respectively. Finite cavities with periodic boundary conditions along the principal axis of the cavities have been considered, where the cavity's principal axis is along the z-direction. We first focus our study in the structure induced by varying the degree of confinement, determining the HSC phase diagram for aspect ratios l/σ = 3, 5, 7, and 9, at a fixed packing fraction η = 0.071. By compressing the cavities along the radial direction, the isotropic phase becomes stable before the nematic phase as the length of the cavities is increased, resulting in a second-order transition. The occurrence of phase transitions has also been determined by varying η for constant values of the cavity's length L. Systems with low aspect ratios, l/σ = 3, 5, 7, and 9, exhibit first-order transitions with chiral, paranematic, and isotropic phases, whereas for larger HSCs, l/σ = 50, 70, and 100, the transitions are second order with paranematic, nematic, and isotropic phases, in contrast with the behavior of non-confined systems, with first-order transitions for isotropic, nematic, smectic-A, and solid phases.

Superradiant phase transition with graphene embedded in one dimensional optical cavity

NASA Astrophysics Data System (ADS)

Li, Benliang; Liu, Tao; Hewak, Daniel W.; Wang, Qi Jie

2018-01-01

We theoretically investigate the cavity QED of graphene embedded in an optical cavity under perpendicular magnetic field. We consider the coupling of cyclotron transition and a multimode cavity described by a multimode Dicke model. This model exhibits a superradiant quantum phase transition, which we describe exactly in an effective Hamiltonian approach. The complete excitation spectrum in both the normal phase and superradiant phase regimes is given. In contrast to the single mode case, multimode coupling of cavity photon and cyclotron transition can greatly reduce the critical vacuum Rabi frequency required for quantum phase transition, and dramatically enhance the superradiant emission by fast modulating the Hamiltonian. Our work paves a way to experimental explorations of quantum phase transitions in solid state systems.

Femtosecond Fiber Lasers

NASA Astrophysics Data System (ADS)

Bock, Katherine J.

This thesis focuses on research I have done on ytterbium-doped femtosecond fiber lasers. These lasers operate in the near infrared region, lasing at 1030 nm. This wavelength is particularly important in biomedical applications, which includes but is not limited to confocal microscopy and ablation for surgical incisions. Furthermore, fiber lasers are advantageous compared to solid state lasers in terms of their cost, form factor, and ease of use. Solid state lasers still dominate the market due to their comparatively high energy pulses. High energy pulse generation in fiber lasers is hindered by either optical wave breaking or by multipulsing. One of the main challenges for fiber lasers is to overcome these limitations to achieve high energy pulses. The motivation for the work done in this thesis is increasing the output pulse peak power and energy. The main idea of the work is that decreasing the nonlinearity that acts on the pulse inside the cavity will prevent optical wave breaking, and thus will generate higher energy pulses. By increasing the output energy, ytterbium-doped femtosecond fiber lasers can be competitive with solid state lasers which are used commonly in research. Although fiber lasers tend to lack the wavelength tuning ability of solid state lasers, many biomedical applications take advantage of the 1030 microm central wavelength of ytterbium-doped fiber lasers, so the major limiting factor of fiber lasers in this field is simply the output power. By increasing the output energy without resorting to external amplification, the cavity is optimized and cost can remain low and economical. During verification of the main idea, the cavity was examined for possible back-reflections and for components with narrow spectral bandwidths which may have contributed to the presence of multipulsing. Distinct cases of multipulsing, bound pulse and harmonic mode-locking, were observed and recorded as they may be of more interest in the future. The third-order dispersion contribution from the diffraction gratings inside the laser cavity was studied, as it was also considered to be an energy-limiting factor. No significant effect was found as a result of third-order dispersion; however, a region of operation was observed where two different pulse regimes were found at the same values of net cavity group velocity dispersion. Results verify the main idea and indicate that a long length of low-doped gain fiber is preferable to a shorter, more highly doped one. The low-doped fiber in an otherwise equivalent cavity allows the nonlinear phase shift to grow at a slower rate, which results in the pulse achieving a higher peak power before reaching the nonlinear phase shift threshold at which optical wave breaking occurs. For a range of net cavity group velocity dispersion values, the final result is that the low doped fiber generates pulses of approximately twice the value of energy of the highly-doped gain fiber. Two techniques of mode-locking cavities were investigated to achieve this result. The first cavity used NPE mode-locking which masked the results, and the second used a SESAM for mode-locking which gave clear results supporting the hypothesis.

Intertwined and vestigial order with ultracold atoms in multiple cavity modes

NASA Astrophysics Data System (ADS)

Gopalakrishnan, Sarang; Shchadilova, Yulia E.; Demler, Eugene

2017-12-01

Atoms in transversely pumped optical cavities "self-organize" by forming a density wave and emitting superradiantly into the cavity mode(s). For a single-mode cavity, the properties of this self-organization transition are well characterized both theoretically and experimentally. Here, we explore the self-organization of a Bose-Einstein condensate in the presence of two cavity modes—a system that recently was realized experimentally [Léonard et al., Nature (London) 543, 87 (2017), 10.1038/nature21067]. We argue that this system can exhibit a "vestigially ordered" phase in which neither cavity mode exhibits superradiance but the cavity modes are mutually phase locked by the atoms. We argue that this vestigially ordered phase should generically be present in multimode cavity geometries.

Acousto-optical interaction of surface acoustic and optical waves in a two-dimensional phoxonic crystal hetero-structure cavity.

PubMed

Ma, Tian-Xue; Zou, Kui; Wang, Yue-Sheng; Zhang, Chuanzeng; Su, Xiao-Xing

2014-11-17

Phoxonic crystal is a promising material for manipulating sound and light simultaneously. In this paper, we theoretically demonstrate the propagation of acoustic and optical waves along the truncated surface of a two-dimensional square-latticed phoxonic crystal. Further, a phoxonic crystal hetero-structure cavity is proposed, which can simultaneously confine surface acoustic and optical waves. The interface motion and photoelastic effects are taken into account in the acousto-optical coupling. The results show obvious shifts in eigenfrequencies of the photonic cavity modes induced by different phononic cavity modes. The symmetry of the phononic cavity modes plays a more important role in the single-phonon exchange process than in the case of the multi-phonon exchange. Under the same deformation, the frequency shift of the photonic transverse electric mode is larger than that of the transverse magnetic mode.

Modeling and experimental investigation of an integrated optical microheater in silicon-on-insulator.

PubMed

Kaushal, Saket; Das, Bijoy Krishna

2016-04-10

A linear piecewise model has been formulated to analyze the performance of a metallic microheater integrated with single-mode waveguides (λ∼1550  nm) in silicon-on-insulator (SOI). The model has been used to evaluate integrated optical microheaters fabricated in a SOI substrate with 2 µm device layer thickness. The Fabry-Perot modulation technique has been used to extract the effective thermo-optic phase shift and response time. The effective thermal power budget of P_eff,π∼500  µW (out of actually consumed power P_π=1.1  mW) for a π phase shift and a switching time of τ∼9  µs, have been recorded for a typical Ti heater stripe of length L_H=50  µm, width W_H=2  µm, and thickness t_H∼150  nm, integrated with a Fabry-Perot waveguide cavity of length ∼20  mm. It has been shown that the performance of a heater improves (in terms of power budget) as the length of a microheater decreases. However, smaller heater size requires higher joule heating to obtain a desired phase shift, which is again found to be dependent on polarization of the guided mode because of thermal stress.

Modulation characteristics of a high-power semiconductor Master Oscillator Power Amplifier (MOPA)

NASA Technical Reports Server (NTRS)

Cornwell, Donald Mitchell, Jr.

1992-01-01

A semiconductor master oscillator-power amplifier was demonstrated using an anti-reflection (AR) coated broad area laser as the amplifier. Under CW operation, diffraction-limited single-longitudinal-mode powers up to 340 mW were demonstrated. The characteristics of the far-field pattern were measured and compared to a two-dimensional reflective Fabry-Perot amplifier model of the device. The MOPA configuration was modulated by the master oscillator. Prior to injection into the amplifier, the amplitude and frequency modulation properties of the master oscillator were characterized. The frequency response of the MOPA configuration was characterized for an AM/FM modulated injection beam, and was found to be a function of the frequency detuning between the master oscillator and the resonant amplifier. A shift in the phase was also observed as a function of frequency detuning; this phase shift is attributed to the optical phase shift imparted to a wave reflected from a Fabry-Perot cavity. Square-wave optical pulses were generated at 10 MHz and 250 MHz with diffraction-limited peak powers of 200 mW and 250 mW. The peak power for a given modulation frequency is found to be limited by the injected power and the FM modulation at that frequency. The modulation results make the MOPA attractive for use as a transmitter source in applications such as free-space communications and ranging/altimetry.

A resonance shift prediction based on the Boltzmann-Ehrenfest principle for cylindrical cavities with a rigid sphere.

PubMed

Santillan, Arturo O; Cutanda-Henríquez, Vicente

2008-11-01

An investigation on the resonance frequency shift for a plane-wave mode in a cylindrical cavity produced by a rigid sphere is reported in this paper. This change of the resonance frequency has been previously considered as a cause of oscillational instabilities in single-mode acoustic levitation devices. It is shown that the use of the Boltzmann-Ehrenfest principle of adiabatic invariance allows the derivation of an expression for the resonance frequency shift in a simpler and more direct way than a method based on a Green's function reported in literature. The position of the sphere can be any point along the axis of the cavity. Obtained predictions of the resonance frequency shift with the deduced equation agree quite well with numerical simulations based on the boundary element method. The results are also confirmed by experiments. The equation derived from the Boltzmann-Ehrenfest principle appears to be more general, and for large spheres, it gives a better approximation than the equation previously reported.

Infiltrated bunch of solitons in Bi-doped frequency-shifted feedback fibre laser operated at 1450 nm

PubMed Central

Rissanen, Joona; Korobko, Dmitry A.; Zolotovsky, Igor O.; Melkumov, Mikhail; Khopin, Vladimir F.; Gumenyuk, Regina

2017-01-01

Mode-locked fibre laser as a dissipative system is characterized by rich forms of soliton interaction, which take place via internal energy exchange through noisy background in the presence of dispersion and nonlinearity. The result of soliton interaction was either stationary-localized or chaotically-oscillated soliton complexes, which have been shown before as stand-alone in the cavity. Here we report on a new form of solitons complex observed in Bi-doped mode-locked fibre laser operated at 1450 nm. The solitons are arranged in two different group types contemporizing in the cavity: one pulse group propagates as bound solitons with fixed phase relation and interpulse position eventuated in 30 dB spectrum modulation depth; while the other pulses form a bunch with continuously and chaotically moving solitons. The article describes both experimental and theoretical considerations of this effect. PMID:28281677

Tunable Graphene Metasurface Reflectarray for Cloaking, Illusion, and Focusing

NASA Astrophysics Data System (ADS)

Biswas, Sudipta Romen; Gutiérrez, Cristian E.; Nemilentsau, Andrei; Lee, In-Ho; Oh, Sang-Hyun; Avouris, Phaedon; Low, Tony

2018-03-01

This paper is a contribution to the Physical Review Applied collection in memory of Mildred S. Dresselhaus. We present a graphene-based metasurface that can be actively tuned between different regimes of operation, such as anomalous beam steering and focusing, cloaking, and illusion optics, by applying electrostatic gating without modifying the geometry of the metasurface. The metasurface is designed by placing graphene ribbons on a dielectric cavity resonator, where interplay between geometric plasmon resonances in the ribbons and Fabry-Perot resonances in the cavity is used to achieve a 2 π phase shift. As a proof of concept, we demonstrate that the wave front of the field reflected from a triangular bump covered by the metasurface can be tuned by applying electric bias so as to resemble that of a bare plane and of a spherical object. Moreover, reflective focusing and the change of the reflection direction for the above mentioned cases are also shown.

Transverse Pupil Shifts for Adaptive Optics Non-Common Path Calibration

NASA Technical Reports Server (NTRS)

Bloemhof, Eric E.

2011-01-01

A simple new way of obtaining absolute wavefront measurements with a laboratory Fizeau interferometer was recently devised. In that case, the observed wavefront map is the difference of two cavity surfaces, those of the mirror under test and of an unknown reference surface on the Fizeau s transmission flat. The absolute surface of each can be determined by applying standard wavefront reconstruction techniques to two grids of absolute surface height differences of the mirror under test, obtained from pairs of measurements made with slight transverse shifts in X and Y. Adaptive optics systems typically provide an actuated periscope between wavefront sensor (WFS) and commonmode optics, used for lateral registration of deformable mirror (DM) to WFS. This periscope permits independent adjustment of either pupil or focal spot incident on the WFS. It would be used to give the required lateral pupil motion between common and non-common segments, analogous to the lateral shifts of the two phase contributions in the lab Fizeau. The technique is based on a completely new approach to calibration of phase. It offers unusual flexibility with regard to the transverse spatial frequency scales probed, and will give results quite quickly, making use of no auxiliary equipment other than that built into the adaptive optics system. The new technique may be applied to provide novel calibration information about other optical systems in which the beam may be shifted transversely in a controlled way.

Selective tuning of high-Q silicon photonic crystal nanocavities via laser-assisted local oxidation.

PubMed

Chen, Charlton J; Zheng, Jiangjun; Gu, Tingyi; McMillan, James F; Yu, Mingbin; Lo, Guo-Qiang; Kwong, Dim-Lee; Wong, Chee Wei

2011-06-20

We examine the cavity resonance tuning of high-Q silicon photonic crystal heterostructures by localized laser-assisted thermal oxidation using a 532 nm continuous wave laser focused to a 2.5 μm radius spot-size. The total shift is consistent with the parabolic rate law. A tuning range of up to 8.7 nm is achieved with ∼ 30 mW laser powers. Over this tuning range, the cavity Qs decreases from 3.2×10(5) to 1.2×10(5). Numerical simulations model the temperature distributions in the silicon photonic crystal membrane and the cavity resonance shift from oxidation.

Phase transition studies in barium and strontium titanates at microwave frequencies

NASA Technical Reports Server (NTRS)

Dahiya, Jai N.

1993-01-01

The objectives were the following: to understand the phase transformations in barium and strontium titanates as the crystals go from one temperature to the other; and to study the dielectric behavior of barium and strontium titanate crystals at a microwave frequency of 9.12 GHz and as a function of temperature. Phase transition studies in barium and strontium titanate are conducted using a cylindrical microwave resonant cavity as a probe. The cavity technique is quite successful in establishing the phase changes in these crystals. It appears that dipole relaxation plays an important role in the behavior of the dielectric response of the medium loading the cavity as phase change takes place within the sample. The method of a loaded resonant microwave cavity as applied in this work has proven to be sensitive enough to monitor small phase changes of the cavity medium.

Mode suppression means for gyrotron cavities

DOEpatents

Chodorow, Marvin; Symons, Robert S.

1983-08-09

In a gyrotron electron tube of the gyro-klystron or gyro-monotron type, having a cavity supporting an electromagnetic mode with circular electric field, spurious resonances can occur in modes having noncircular electric field. These spurious resonances are damped and their frequencies shifted by a circular groove in the cavity parallel to the electric field.

Analog detection for cavity lifetime spectroscopy

DOEpatents

Zare, Richard N.; Harb, Charles C.; Paldus, Barbara A.; Spence, Thomas G.

2001-05-15

An analog detection system for determining a ring-down rate or decay rate 1/.tau. of an exponentially decaying ring-down beam issuing from a lifetime or ring-down cavity during a ring-down phase. Alternatively, the analog detection system determines a build-up rate of an exponentially growing beam issuing from the cavity during a ring-up phase. The analog system can be employed in continuous wave cavity ring-down spectroscopy (CW CRDS) and pulsed CRDS (P CRDS) arrangements utilizing any type of ring-down cavity including ring-cavities and linear cavities.

Analog detection for cavity lifetime spectroscopy

DOEpatents

Zare, Richard N.; Harb, Charles C.; Paldus, Barbara A.; Spence, Thomas G.

2003-01-01

An analog detection system for determining a ring-down rate or decay rate 1/.tau. of an exponentially decaying ring-down beam issuing from a lifetime or ring-down cavity during a ring-down phase. Alternatively, the analog detection system determines a build-up rate of an exponentially growing beam issuing from the cavity during a ring-up phase. The analog system can be employed in continuous wave cavity ring-down spectroscopy (CW CRDS) and pulsed CRDS (P CRDS) arrangements utilizing any type of ring-down cavity including ring-cavities and linear cavities.

Acoustic levitation and the Boltzmann-Ehrenfest principle

NASA Technical Reports Server (NTRS)

Putterman, S.; Rudnick, Joseph; Barmatz, M.

1989-01-01

The Boltzmann-Ehrenfest principle of adiabatic invariance relates the acoustic potential acting on a sample positioned in a single-mode cavity to the shift in resonant frequency caused by the presence of this sample. This general and simple relation applies to samples and cavities of arbitrary shape, dimension, and compressibility. Positioning forces and torques can, therefore, be determined from straightforward measurements of frequency shifts. Applications to the Rayleigh disk phenomenon and levitated cylinders are presented.

All-optical on-chip sensor for high refractive index sensing

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

Liu, Yazhao; Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ, Delft; Salemink, H. W. M., E-mail: H.Salemink@science.ru.nl

2015-01-19

A highly sensitive sensor design based on two-dimensional photonic crystal cavity is demonstrated. The geometric structure of the cavity is modified to gain a high quality factor, which enables a sensitive refractive index sensing. A group of slots with optimized parameters is created in the cavity. The existence of the slots enhances the light-matter interactions between confined photons and analytes. The interactions result in large wavelength shifts in the transmission spectra and are denoted by high sensitivities. Experiments show that a change in refractive index of Δn ∼ 0.12 between water and oil sample 1 causes a spectral shift of 23.5 nm, andmore » the spectral shift between two oil samples is 5.1 nm for Δn ∼ 0.039. These results are in good agreement with simulations, which are 21.3 and 7.39 nm for the same index changes.« less

FPGA-Based Optical Cavity Phase Stabilization for Coherent Pulse Stacking

DOE PAGES

Xu, Yilun; Wilcox, Russell; Byrd, John; ...

2017-11-20

Coherent pulse stacking (CPS) is a new time-domain coherent addition technique that stacks several optical pulses into a single output pulse, enabling high pulse energy from fiber lasers. We develop a robust, scalable, and distributed digital control system with firmware and software integration for algorithms, to support the CPS application. We model CPS as a digital filter in the Z domain and implement a pulse-pattern-based cavity phase detection algorithm on an field-programmable gate array (FPGA). A two-stage (2+1 cavities) 15-pulse stacking system achieves an 11.0 peak-power enhancement factor. Each optical cavity is fed back at 1.5kHz, and stabilized at anmore » individually-prescribed round-trip phase with 0.7deg and 2.1deg rms phase errors for Stages 1 and 2, respectively. Optical cavity phase control with nanometer accuracy ensures 1.2% intensity stability of the stacked pulse over 12 h. The FPGA-based feedback control system can be scaled to large numbers of optical cavities.« less

FPGA-Based Optical Cavity Phase Stabilization for Coherent Pulse Stacking

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

Xu, Yilun; Wilcox, Russell; Byrd, John

Coherent pulse stacking (CPS) is a new time-domain coherent addition technique that stacks several optical pulses into a single output pulse, enabling high pulse energy from fiber lasers. We develop a robust, scalable, and distributed digital control system with firmware and software integration for algorithms, to support the CPS application. We model CPS as a digital filter in the Z domain and implement a pulse-pattern-based cavity phase detection algorithm on an field-programmable gate array (FPGA). A two-stage (2+1 cavities) 15-pulse stacking system achieves an 11.0 peak-power enhancement factor. Each optical cavity is fed back at 1.5kHz, and stabilized at anmore » individually-prescribed round-trip phase with 0.7deg and 2.1deg rms phase errors for Stages 1 and 2, respectively. Optical cavity phase control with nanometer accuracy ensures 1.2% intensity stability of the stacked pulse over 12 h. The FPGA-based feedback control system can be scaled to large numbers of optical cavities.« less

Optical gyroscope with controllable dispersion in four wave mixing regime.

NASA Astrophysics Data System (ADS)

Mikhailov, Eugeniy; Wolfe, Owen; Du, Shuangli; Rochester, Simon; Budker, Dmitry; Novikova, Irina

2016-05-01

We present our work towards realization of the fast-light gyroscope prototype, in which the sensitivity enhancement (compared to a regular laser gyroscopes) is achieved by adjusting the intra-cavity dispersion. We discuss schematics and underlying nonlinear effects leading to the negative dispersion in Rb vapor: level structure, optically addressed transitions, and configuration of the resonant cavity. We investigate dependence of the pulling factor (i.e., the ratio of the lasing frequency shift with the change of the cavity length to the equivalent resonance frequency shift in the empty cavity) on pump lasers detunings, power, and density of the atomic vapor. The observation of the pulling factor exceeding unity implies the gyroscope sensitivity improvement over the regular system This work is supported by Naval Air Warfare Center STTR program N68335-11-C-0428.

Automatic Phase Calibration for RF Cavities using Beam-Loading Signals

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

Edelen, J. P.; Chase, B. E.

Precise calibration of the cavity phase signals is necessary for the operation of any particle accelerator. For many systems this requires human in the loop adjustments based on measurements of the beam parameters downstream. Some recent work has developed a scheme for the calibration of the cavity phase using beam measurements and beam-loading however this scheme is still a multi-step process that requires heavy automation or human in the loop. In this paper we analyze a new scheme that uses only RF signals reacting to beam-loading to calculate the phase of the beam relative to the cavity. This technique couldmore » be used in slow control loops to provide real-time adjustment of the cavity phase calibration without human intervention thereby increasing the stability and reliability of the accelerator.« less

Phase-locking of an axisymmetric-fold combination cavity CO2 laser using the back surface of the output-mirror

NASA Astrophysics Data System (ADS)

Xu, Yonggen; Li, Yude; Feng, Ting; Qiu, Yi

2009-12-01

The principle of phase-locking of an axisymmetric fold combination cavity CO2 laser, fulfilled by the reflection-injection of the back surface of the output-mirror, has been studied in detail. Variation of the equiphase surface and the influence of some characteristic parameters on phase-locking are analyzed—for example, phase error, changes in the cavity length and curvature radius, line-width and temperature. It is shown that the injected beam can excite a stable mode in the cavities, and the value of the energy coupling coefficient directly reflects the degree of phase-locking. Therefore, the output beams have a fixed phase relation between each other, and good coherent beams can be obtained by using the phase-locking method.

Active material, optical mode and cavity impact on nanoscale electro-optic modulation performance

NASA Astrophysics Data System (ADS)

Amin, Rubab; Suer, Can; Ma, Zhizhen; Sarpkaya, Ibrahim; Khurgin, Jacob B.; Agarwal, Ritesh; Sorger, Volker J.

2017-10-01

Electro-optic modulation is a key function in optical data communication and possible future optical compute engines. The performance of modulators intricately depends on the interaction between the actively modulated material and the propagating waveguide mode. While a variety of high-performance modulators have been demonstrated, no comprehensive picture of what factors are most responsible for high performance has emerged so far. Here we report the first systematic and comprehensive analytical and computational investigation for high-performance compact on-chip electro-optic modulators by considering emerging active materials, model considerations and cavity feedback at the nanoscale. We discover that the delicate interplay between the material characteristics and the optical mode properties plays a key role in defining the modulator performance. Based on physical tradeoffs between index modulation, loss, optical confinement factors and slow-light effects, we find that there exist combinations of bias, material and optical mode that yield efficient phase or amplitude modulation with acceptable insertion loss. Furthermore, we show how material properties in the epsilon near zero regime enable reduction of length by as much as by 15 times. Lastly, we introduce and apply a cavity-based electro-optic modulator figure of merit, Δλ/Δα, relating obtainable resonance tuning via phase shifting relative to the incurred losses due to the fundamental Kramers-Kronig relations suggesting optimized device operating regions with optimized modulation-to-loss tradeoffs. This work paves the way for a holistic design rule of electro-optic modulators for high-density on-chip integration.

Research Progress on F-P Interference—Based Fiber-Optic Sensors

PubMed Central

Huang, Yi Wen; Tao, Jin; Huang, Xu Guang

2016-01-01

We review our works on Fabry-Perot (F-P) interferometric fiber-optic sensors with various applications. We give a general model of F-P interferometric optical fiber sensors including diffraction loss caused by the beam divergence and the Gouy phase shift. Based on different structures of an F-P cavity formed on the end of a single-mode fiber, the F-P interferometric optical sensor has been extended to measurements of the refractive index (RI) of liquids and solids, temperature as well as small displacement. The RI of liquids and solids can be obtained by monitoring the fringe contrast related to Fresnel reflections, while the ambient temperature and small displacement can be obtained by monitoring the wavelength shift of the interference fringes. The F-P interferometric fiber-optic sensors can be used for many scientific and technological applications. PMID:27598173

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

Dubey, Manvendra; Aiken, Allison; Berg, Larry K.

We deployed Aerodyne Research Inc.’s first Cavity Attenuated Phase Shift extinction (CAPS PMex) monitor (built by Aerodyne) that measures light extinction by using a visible-light-emitting diode (LED) as a light source, a sample cell incorporating two high-reflectivity mirrors centered at the wavelength of the LED, and a vacuum photodiode detector in Cape Cod in 2012/13 for the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility’s Two-Column Aerosol Project (TCAP). The efficacy of this instrument is based on the fact that aerosols are broadband scatterers and absorbers of light. The input LED is square-wave modulated and passedmore » through the sample cell that distorts it due to exponential decay by aerosol light absorption and scattering; this is measured at the detector. The amount of phase shift of the light at the detector is used to determine the light extinction. This extinction measurement provides an absolute value, requiring no calibration. The goal was to compare the CAPS performance with direct measurements of absorption with ARM’s baseline photoacoustic soot spectrometer (PASS-3) and nephelometer instruments to evaluate its performance.« less

Micrometer-Scale Ballistic Transport of Electron Pairs in LaAlO_{3}/SrTiO_{3} Nanowires.

PubMed

Tomczyk, Michelle; Cheng, Guanglei; Lee, Hyungwoo; Lu, Shicheng; Annadi, Anil; Veazey, Joshua P; Huang, Mengchen; Irvin, Patrick; Ryu, Sangwoo; Eom, Chang-Beom; Levy, Jeremy

2016-08-26

High-mobility complex-oxide heterostructures and nanostructures offer new opportunities for extending the paradigm of quantum transport beyond the realm of traditional III-V or carbon-based materials. Recent quantum transport investigations with LaAlO_{3}/SrTiO_{3}-based quantum dots reveal the existence of a strongly correlated phase in which electrons form spin-singlet pairs without becoming superconducting. Here, we report evidence for the micrometer-scale ballistic transport of electron pairs in quasi-1D LaAlO_{3}/SrTiO_{3} nanowire cavities. In the paired phase, Fabry-Perot-like quantum interference is observed, in sync with conductance oscillations observed in the superconducting regime (at a zero magnetic field). Above a critical magnetic field B_{p}, the electron pairs unbind and the conductance oscillations shift with the magnetic field. These experimental observations extend the regime of ballistic electronic transport to strongly correlated phases.

Phase demodulation of Fabry-Perot interferometer-based acoustic sensor utilizing tunable filter with two quadrature wavelengths

NASA Astrophysics Data System (ADS)

Liao, Hao; Lu, Ping; Liu, Li; Liu, Deming; Zhang, Jiangshan

2017-02-01

A phase demodulation method for short-cavity extrinsic Fabry-Perot interferometer (EFPI) based on two orthogonal wavelengths via a tunable optical filter is proposed in this paper. A broadband light is launched into the EFPI sensor and two monochromatic beams with 3dB bandwidth of 0.2nm are selected out from the reflected light of the EFPI sensor. A phase bias is induced between the two interferential signals due to the wavelength difference of the two beams. The wavelength difference will have an affect on the sensitivity of demodulated signal, which has been theoretically and experimentally demonstrated. The maximum sensitivity can be obtained when the phase bias is 0.5π corresponding to the wavelength difference of 1/4 FSR of the EFPI spectrum. The acoustic wave induced phase variation can be interrogated through an optimized differential cross multiplication (DCM) method. A normalization process is induced into the traditional DCM method to eliminate the influence of ambient temperature and pressure fluctuation induced spectrum shift on output signal. This means that, once the wavelength difference is fixed, the wavelength variation of each individual beam will have little influence on the amplitude of demodulated signal. The EFPI sensing head is formed by a 3μm-thick aluminum diaphragm, which has a SNR of more than 53dB. Through the proposed demodulation scheme, a large dynamic range and good linearity is acquired and Q-point drift problem of traditional EFPI sensor can be solved. The demodulation scheme can be applied to other kinds of short-cavity EFPI based acoustic sensors.

Computational Study of Fluidic Thrust Vectoring using Separation Control in a Nozzle

NASA Technical Reports Server (NTRS)

Deere, Karen; Berrier, Bobby L.; Flamm, Jeffrey D.; Johnson, Stuart K.

2003-01-01

A computational investigation of a two- dimensional nozzle was completed to assess the use of fluidic injection to manipulate flow separation and cause thrust vectoring of the primary jet thrust. The nozzle was designed with a recessed cavity to enhance the throat shifting method of fluidic thrust vectoring. The structured-grid, computational fluid dynamics code PAB3D was used to guide the design and analyze over 60 configurations. Nozzle design variables included cavity convergence angle, cavity length, fluidic injection angle, upstream minimum height, aft deck angle, and aft deck shape. All simulations were computed with a static freestream Mach number of 0.05. a nozzle pressure ratio of 3.858, and a fluidic injection flow rate equal to 6 percent of the primary flow rate. Results indicate that the recessed cavity enhances the throat shifting method of fluidic thrust vectoring and allows for greater thrust-vector angles without compromising thrust efficiency.

High sensitivity rotation sensing based on tunable asymmetrical double-ring structure

NASA Astrophysics Data System (ADS)

Gu, Hong; Liu, Xiaoqing

2017-05-01

A very high sensitivity rotation sensor comprising a tunable asymmetrical double-ring structure (TADRS) coupled by a 3 × 3 coupler is presented. The phase difference caused by the TADRS between the counter-propagating waves is derived and discussed. At the resonant frequency, the phase shift difference has the maximum value when the light power in one cavity is amplified about 1.85 times while attenuated 79% in another. The maximum sensitivity of the TADRS sensor is two times larger than that of a single-ring structure. An experimental system is designed to verify the theoretical results and introduce the method of demodulation. The rotation sensor based on TADRS can enhance the sensitivity of the detection of the angular velocity by more than three orders of magnitude.

Stimulated Brillouin scattering in ultra-long distributed feedback Bragg gratings in standard optical fiber.

PubMed

Loranger, Sébastien; Lambin-Iezzi, Victor; Wahbeh, Mamoun; Kashyap, Raman

2016-04-15

Distributed feedback (DFB) fiber Bragg gratings (FBG) are widely used as narrow-band filters and single-mode cavities for lasers. Recently, a nonlinear generation has been shown in 10-20 cm DFB gratings in a highly nonlinear fiber. First, we show in this Letter a novel fabrication technique of ultra-long DFBs in a standard fiber (SMF-28). Second, we demonstrate nonlinear generation in such gratings. A particular inscription technique was used to fabricate all-in-phase ultra-long FBG and to implement reproducible phase shift to form a DFB mode. We demonstrate stimulated Brillouin scattering (SBS) emission from this DFB mode and characterize the resulting laser. It seems that such a SBS based DFB laser stabilizes a pump's jittering and reduces its linewidth.

Phase difference in modulated signals of two orthogonally polarized outputs of a Nd:YAG microchip laser with anisotropic optical feedback.

PubMed

Zhang, Peng; Tan, Yi-Dong; Liu, Ning; Wu, Yun; Zhang, Shu-Lian

2013-11-01

We present an experimental observation of the output responses of a Nd:YAG microchip laser with an anisotropic external cavity under weak optical feedback. The feedback mirror is stationary during the experiments. A pair of acousto-optic modulators is used to produce a frequency shift in the feedback light with respect to the initial light. The laser output is a beat signal with 40 kHz modulation frequency and is separated into two orthogonal directions by a Wollaston prism. Phase differences between the two intensity curves are observed as the laser works in two orthogonal modes, and vary with the external birefringence element and the pump power. Theoretical analyses are given, and the simulated results are consistent with the experimental phenomena.

Multi-target-qubit unconventional geometric phase gate in a multi-cavity system

NASA Astrophysics Data System (ADS)

Liu, Tong; Cao, Xiao-Zhi; Su, Qi-Ping; Xiong, Shao-Jie; Yang, Chui-Ping

2016-02-01

Cavity-based large scale quantum information processing (QIP) may involve multiple cavities and require performing various quantum logic operations on qubits distributed in different cavities. Geometric-phase-based quantum computing has drawn much attention recently, which offers advantages against inaccuracies and local fluctuations. In addition, multiqubit gates are particularly appealing and play important roles in QIP. We here present a simple and efficient scheme for realizing a multi-target-qubit unconventional geometric phase gate in a multi-cavity system. This multiqubit phase gate has a common control qubit but different target qubits distributed in different cavities, which can be achieved using a single-step operation. The gate operation time is independent of the number of qubits and only two levels for each qubit are needed. This multiqubit gate is generic, e.g., by performing single-qubit operations, it can be converted into two types of significant multi-target-qubit phase gates useful in QIP. The proposal is quite general, which can be used to accomplish the same task for a general type of qubits such as atoms, NV centers, quantum dots, and superconducting qubits.

Multi-target-qubit unconventional geometric phase gate in a multi-cavity system.

PubMed

Liu, Tong; Cao, Xiao-Zhi; Su, Qi-Ping; Xiong, Shao-Jie; Yang, Chui-Ping

2016-02-22

Cavity-based large scale quantum information processing (QIP) may involve multiple cavities and require performing various quantum logic operations on qubits distributed in different cavities. Geometric-phase-based quantum computing has drawn much attention recently, which offers advantages against inaccuracies and local fluctuations. In addition, multiqubit gates are particularly appealing and play important roles in QIP. We here present a simple and efficient scheme for realizing a multi-target-qubit unconventional geometric phase gate in a multi-cavity system. This multiqubit phase gate has a common control qubit but different target qubits distributed in different cavities, which can be achieved using a single-step operation. The gate operation time is independent of the number of qubits and only two levels for each qubit are needed. This multiqubit gate is generic, e.g., by performing single-qubit operations, it can be converted into two types of significant multi-target-qubit phase gates useful in QIP. The proposal is quite general, which can be used to accomplish the same task for a general type of qubits such as atoms, NV centers, quantum dots, and superconducting qubits.

Novel design of electrical sensing interface for prosthetic limbs using optical micro cavities

NASA Astrophysics Data System (ADS)

Ali, Amir R.; Kamel, Mohamed A.

2018-04-01

This paper uses optical whispering galley modes (WGM) cavities to construct a new electrical sensing interface between prosthetic limb and the brain. The sensing element will detect the action potential signal in the neural membrane and the prosthetic limb will be actuated accordingly. The element is a WGM dielectric polymeric cavity. WGM based optical cavities can achieve very high values of sensitivity and quality factor; thus, any minute perturbations in the morphology of the cavity can be captured and measured. The action potential signal will produce an applied external electric field on the dielectric cavity causing it to deform due to the electrostriction effect. The resulting deformation will cause WGM shifts in the transmission spectrum of the cavity. Thus, the action potential or the applied electric field can be measured using these shifts. In this paper the action potential signal will be simulated through the use of a function generator and two metal electrodes. The sensing element will be situated between these electrodes to detect the electrical signal passing through. The achieved sensitivity is 27.5 pm/V in measuring the simulated action potential signal; and 0.32 pm/V.m-1 in measuring the applied electric field due to the passage of the simulated signal.

RF kicker cavity to increase control in common transport lines

DOEpatents

Douglas, David R.; Ament, Lucas J. P.

2017-04-18

A method of controlling e-beam transport where electron bunches with different characteristics travel through the same beam pipe. An RF kicker cavity is added at the beginning of the common transport pipe or at various locations along the common transport path to achieve independent control of different bunch types. RF energy is applied by the kicker cavity kicks some portion of the electron bunches, separating the bunches in phase space to allow independent control via optics, or separating bunches into different beam pipes. The RF kicker cavity is operated at a specific frequency to enable kicking of different types of bunches in different directions. The phase of the cavity is set such that the selected type of bunch passes through the cavity when the RF field is at a node, leaving that type of bunch unaffected. Beam optics may be added downstream of the kicker cavity to cause a further separation in phase space.

Intracavity brillouin scattering from passive Q-spoiling cells.

PubMed

Wick, R V; Guenther, A H

1968-01-01

Stimulated Brillouin scattering from the methanol solvent used in conjunction with cryptocyanine bleachable dye in a ruby laser cavity has been observed at low megawatt output powers. The frequency shifts of the Brillouin scattered radiation produced within the laser cavity are slightly less than frequency shifts produced in an external methanol cell. The Brillouin radiation was eliminated even at output power levels in excess of 250 MW when a 3-mm length cell was used in place of the 25.4-mm commercial cell.

Resonance-shifting luminescent solar concentrators

DOEpatents

Giebink, Noel Christopher; Wiederrecht, Gary P; Wasielewski, Michael R

2014-09-23

An optical system and method to overcome luminescent solar concentrator inefficiencies by resonance-shifting, in which sharply directed emission from a bi-layer cavity into a glass substrate returns to interact with the cavity off-resonance at each subsequent reflection, significantly reducing reabsorption loss en route to the edges. In one embodiment, the system comprises a luminescent solar concentrator comprising a transparent substrate, a luminescent film having a variable thickness; and a low refractive index layer disposed between the transparent substrate and the luminescent film.

Resonance-shifting luminescent solar concentrators

DOEpatents

Giebink, Noel Christopher; Wiederrecht, Gary P.; Wasielewski, Michael R.

2018-01-23

An optical system and method to overcome luminescent solar concentrator inefficiencies by resonance-shifting, in which sharply directed emission from a bi-layer cavity into a glass substrate returns to interact with the cavity off-resonance at each subsequent reflection, significantly reducing reabsorption loss en route to the edges. In one embodiment, the system comprises a luminescent solar concentrator comprising a transparent substrate, a luminescent film having a variable thickness; and a low refractive index layer disposed between the transparent substrate and the luminescent film.

Electric-optic resonant phase modulator

NASA Technical Reports Server (NTRS)

Chen, Chien-Chung (Inventor); Robinson, Deborah L. (Inventor); Hemmati, Hamid (Inventor)

1994-01-01

An electro-optic resonant cavity is used to achieve phase modulation with lower driving voltages. Laser damage thresholds are inherently higher than with previously used integrated optics due to the utilization of bulk optics. Phase modulation is achieved at higher speeds with lower driving voltages than previously obtained with non-resonant electro-optic phase modulators. The instant scheme uses a data locking dither approach as opposed to the conventional sinusoidal locking schemes. In accordance with a disclosed embodiment, a resonant cavity modulator has been designed to operate at a data rate in excess of 100 Mbps. By carefully choosing the cavity finesse and its dimension, it is possible to control the pulse switching time to within 4 ns and to limit the required switching voltage to within 10 V. Experimentally, the resonant cavity can be maintained on resonance with respect to the input laser signal by monitoring the fluctuation of output intensity as the cavity is switched. This cavity locking scheme can be applied by using only the random data sequence, and without the need of additional dithering of the cavity. Compared to waveguide modulators, the resonant cavity has a comparable modulating voltage requirement. Because of its bulk geometry, resonant cavity modulator has the potential of accommodating higher throughput power. Furthermore, mode matching into a bulk device is easier and typically can be achieved with higher efficiency. On the other hand, unlike waveguide modulators which are essentially traveling wave devices, the resonant cavity modulator requires that the cavity be maintained in resonance with respect to the incoming laser signal. An additional control loop is incorporated into the modulator to maintain the cavity on resonance.

Phase control and fast start-up of a magnetron using modulation of an addressable faceted cathode

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

Browning, J., E-mail: JimBrowning@BoiseState.edu; Fernandez-Gutierrez, S.; Lin, M. C.

The use of an addressable, faceted cathode has been proposed as a method of modulating current injection in a magnetron to improve performance and control phase. To implement the controllable electron emission, five-sided and ten-sided faceted planar cathodes employing gated field emitters are considered as these emitters could be fabricated on flat substrates. For demonstration, the conformal finite-difference time-domain particle-in-cell simulation, as implemented in VORPAL, has been used to model a ten-cavity, rising sun magnetron using the modulated current sources and benchmarked against a typical continuous current source. For the modulated, ten-sided faceted cathode case, the electrons are injected frommore » three emitter elements on each of the ten facets. Each emitter is turned ON and OFF in sequence at the oscillating frequency with five emitters ON at one time to drive the five electron spokes of the π-mode. The emitter duty cycle is then 1/6th the Radio-Frequency (RF) period. Simulations show a fast start-up time as low as 35 ns for the modulated case compared to 100 ns for the continuous current cases. Analysis of the RF phase using the electron spoke locations and the RF magnetic field components shows that the phase is controlled for the modulated case while it is random, as typical, for the continuous current case. Active phase control during oscillation was demonstrated by shifting the phase of the electron injection 180° after oscillations started. The 180° phase shift time was approximately 25 RF cycles.« less

Low-power, ultrafast, and dynamic all-optical tunable plasmon induced transparency in two stub resonators side-coupled with a plasmonic waveguide system

NASA Astrophysics Data System (ADS)

Wang, Boyun; Zeng, Qingdong; Xiao, Shuyuan; Xu, Chen; Xiong, Liangbin; Lv, Hao; Du, Jun; Yu, Huaqing

2017-11-01

We theoretically and numerically investigate a low-power, ultrafast, and dynamic all-optical tunable plasmon induced transparency (PIT) in two stub resonators side-coupled with a metal-dielectric-metal (MDM) plasmonic waveguide system. The optical Kerr effect is enhanced by the local electromagnetic field of surface plasmon polaritons (SPPs) and the plasmonic waveguide based on graphene-Ag composite material structures with large effective Kerr nonlinear coefficient. An ultrafast response time of the order of 1 ps is reached because of ultrafast carrier relaxation dynamics of graphene. With dynamically tuning the propagation phase of the plasmonic waveguide, π-phase shift of the transmission spectrum in the PIT system is achieved under excitation of a pump light with an intensity as low as 5.8 MW cm-2. The group delay is controlled between 0.14 and 0.67 ps. Moreover, the tunable bandwidth of about 42 nm is obtained. For the indirect coupling between two stub cavities or the phase coupling scheme, the phase shift multiplication effect of the PIT effect is found. All observed schemes are analyzed rigorously through finite-difference time-domain simulations and coupled-mode formalism. This work not only paves the way towards the realization of on-chip integrated nanophotonic devices but also opens the possibility of the construction of ultrahigh-speed information processing chips based on plasmonic circuits.

Thermal analysis of void cavity for heat pipe receiver under microgravity

NASA Astrophysics Data System (ADS)

Gui, Xiaohong; Song, Xiange; Nie, Baisheng

2017-04-01

Based on theoretical analysis of PCM (Phase Change Material) solidification process, the model of improved void cavity distribution tending to high temperature region is established. Numerical results are compared with NASA (National Aeronautics and Space Administration) results. Analysis results show that the outer wall temperature, the melting ratio of PCM and the temperature gradient of PCM canister, have great difference in different void cavity distribution. The form of void distribution has a great effect on the process of phase change. Based on simulation results under the model of improved void cavity distribution, phase change heat transfer process in thermal storage container is analyzed. The main goal of the improved designing for PCM canister is to take measures in reducing the concentration distribution of void cavity by adding some foam metal into phase change material.

Carrier-Envelope Phase Effects in Plasma-Based Electron Acceleration with Few-Cycle Laser Pulses

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

Nerush, E. N.; Kostyukov, I. Yu.

2009-07-17

Carrier-envelope phase effects during the interaction of relativistically intense few-cycle laser pulses with a plasma are studied in the 'bubble' regime when an electron cavity (bubble) is formed behind the pulse. We show that for few-cycle laser pulses the cavity shape becomes asymmetric and depends strongly on the carrier-envelope phase. The carrier-envelope phase varies when the laser pulse propagates in plasma, which causes transverse oscillations of the cavity. Furthermore, the beam of electrons trapped by the cavity becomes modulated in the polarization plane. To describe these effects we derive an analytical model extended beyond the ponderomotive approximation. The degree ofmore » plasma cavity asymmetry as a function of the laser-plasma parameters is calculated. The obtained results are verified by particle-in-cell simulations.« less

Brillouin lasing in coupled silica toroid microcavities

NASA Astrophysics Data System (ADS)

Honda, Yoshihiro; Yoshiki, Wataru; Tetsumoto, Tomohiro; Fujii, Shun; Furusawa, Kentaro; Sekine, Norihiko; Tanabe, Takasumi

2018-05-01

We demonstrate stimulated Brillouin scattering lasing in a strongly coupled microcavity system. By coupling two silica toroid microcavities, we achieve large mode splitting of 11 GHz, whose frequency separation matches the Brillouin frequency shift of silica. The stimulated Brillouin scattering light is resonantly amplified by pumping at the higher frequency side of the supermode splitting resonance. Since the mode splitting is adjusted by changing the gap distance between the two cavities, our system does not require precise control of a mm-sized cavity diameter to match the free-spectral spacing with the Brillouin frequency shift. It also allows us to use a small cavity, and hence, our system has the potential to achieve the lasing threshold at a very low power.

Vacuum Bloch-Siegert shift in Landau polaritons with ultra-high cooperativity

NASA Astrophysics Data System (ADS)

Li, Xinwei; Bamba, Motoaki; Zhang, Qi; Fallahi, Saeed; Gardner, Geoff C.; Gao, Weilu; Lou, Minhan; Yoshioka, Katsumasa; Manfra, Michael J.; Kono, Junichiro

2018-06-01

A two-level system resonantly interacting with an a.c. magnetic or electric field constitutes the physical basis of diverse phenomena and technologies. However, Schrödinger's equation for this seemingly simple system can be solved exactly only under the rotating-wave approximation, which neglects the counter-rotating field component. When the a.c. field is sufficiently strong, this approximation fails, leading to a resonance-frequency shift known as the Bloch-Siegert shift. Here, we report the vacuum Bloch-Siegert shift, which is induced by the ultra-strong coupling of matter with the counter-rotating component of the vacuum fluctuation field in a cavity. Specifically, an ultra-high-mobility two-dimensional electron gas inside a high-Q terahertz cavity in a quantizing magnetic field revealed ultra-narrow Landau polaritons, which exhibited a vacuum Bloch-Siegert shift up to 40 GHz. This shift, clearly distinguishable from the photon-field self-interaction effect, represents a unique manifestation of a strong-field phenomenon without a strong field.

Electro-optic resonant phase modulator

NASA Technical Reports Server (NTRS)

Chen, Chien-Chung (Inventor); Hemmati, Hamid (Inventor); Robinson, Deborah L. (Inventor)

1992-01-01

An electro-optic resonant cavity is used to achieve phase modulation with lower driving voltages. Laser damage thresholds are inherently higher than with previously used integrated optics due to the utilization of bulk optics. Phase modulation is achieved at higher speeds with lower driving voltages than previously obtained with non-resonant electro-optic phase modulators. The instant scheme uses a data locking dither approach as opposed to the conventional sinusoidal locking schemes. In accordance with a disclosed embodiment, a resonant cavity modulator has been designed to operate at a data rate in excess of 100 megabits per sec. By carefully choosing the cavity finesse and its dimension, it is possible to control the pulse switching time to within 4 nano-sec. and to limit the required switching voltage to within 10 V. This cavity locking scheme can be applied by using only the random data sequence, and without the need of dithering of the cavity. Compared to waveguide modulators, the resonant cavity has a comparable modulating voltage requirement. Because of its bulk geometry, the resonant cavity modulator has the potential of accommodating higher throughput power. Mode matching into the bulk device is easier and typically can be achieved with higher efficiency. An additional control loop is incorporated into the modulator to maintain the cavity on resonance.

Tunable-cavity QED with phase qubits

NASA Astrophysics Data System (ADS)

Whittaker, Jed D.; da Silva, Fabio; Allman, Michael Shane; Lecocq, Florent; Cicak, Katarina; Sirois, Adam; Teufel, John; Aumentado, Jose; Simmonds, Raymond W.

2014-03-01

We describe a tunable-cavity QED architecture with an rf SQUID phase qubit inductively coupled to a single-mode, resonant cavity with a tunable frequency that allows for both tunneling and dispersive measurements. Dispersive measurement is well characterized by a three-level model, strongly dependent on qubit anharmonicity, qubit-cavity coupling and detuning. The tunable cavity frequency provides dynamic control over the coupling strength and qubit-cavity detuning helping to minimize Purcell losses and cavity-induced dephasing during qubit operation. The maximum decay time T1 = 1 . 5 μs is limited by dielectric losses from a design geometry similar to planar transmon qubits. This work supported by NIST and NSA grant EAO140639.

Spontaneous dressed-state polarization in the strong driving regime of cavity QED.

PubMed

Armen, Michael A; Miller, Anthony E; Mabuchi, Hideo

2009-10-23

We utilize high-bandwidth phase-quadrature homodyne measurement of the light transmitted through a Fabry-Perot cavity, driven strongly and on resonance, to detect excess phase noise induced by a single intracavity atom. We analyze the correlation properties and driving-strength dependence of the atom-induced phase noise to establish that it corresponds to the long-predicted phenomenon of spontaneous dressed-state polarization. Our experiment thus provides a demonstration of cavity quantum electrodynamics in the strong-driving regime in which one atom interacts strongly with a many-photon cavity field to produce novel quantum stochastic behavior.

Diaphragm based long cavity Fabry-Perot fiber acoustic sensor using phase generated carrier

NASA Astrophysics Data System (ADS)

Liu, Bin; Lin, Jie; Liu, Huan; Ma, Yuan; Yan, Lei; Jin, Peng

2017-01-01

A diaphragm based long cavity Fabry-Perot interferometric fiber acoustic sensor is proposed. The Fabry-Perot cavity is formed by a flat fiber facet and an ultra-thin silver diaphragm with a 6-meter long fiber inserted in the cavity. A narrow-linewidth ring-cavity erbium-doped fiber laser is applied to demodulate the sensing signal in the phase generated carrier algorithm. Experimental results have demonstrated that the phase sensitivity is about -140 dB re 1 rad/μPa at 2 kHz. The noise equivalent acoustic signal level is 60.6 μPa/Hz1/2 and the dynamic range is 65.1 dB-SPL at 2 kHz. The sensor is suitable for sensing of weak acoustic signals.

ELECTRONIC PHASE CONTROL CIRCUIT

DOEpatents

Salisbury, J.D.; Klein, W.W.; Hansen, C.F.

1959-04-21

An electronic circuit is described for controlling the phase of radio frequency energy applied to a multicavity linear accelerator. In one application of the circuit two cavities are excited from a single radio frequency source, with one cavity directly coupled to the source and the other cavity coupled through a delay line of special construction. A phase detector provides a bipolar d-c output signal proportional to the difference in phase between the voltage in the two cavities. This d-c signal controls a bias supply which provides a d-c output for varying the capacitnce of voltage sensitive capacitors in the delay line. The over-all operation of the circuit is completely electronic, overcoming the time response limitations of the electromechanical control systems, and the relative phase relationship of the radio frequency voltages in the two caviiies is continuously controlled to effect particle acceleration.

Resonant Frequency Shifts of a Fluid Filled Cavity Caused by a Bubble

NASA Astrophysics Data System (ADS)

Zhang, Hailan; Wang, Xiuming; Chen, Dehua; Che, Chengxuan

2009-03-01

In the previous studies for estimating acoustic wave velocities and attenuations of a rock specimen in a low frequency range using an acoustic resonance spectroscopy method, it was found that bubbles in a fluid filled cavity reduce the resonant frequency of the cavity significantly, which makes the measurement unstable. In this paper, this phenomenon is explained by using a simple model of a spherical fluid filled cavity with a single air bubble. It is pointed out that air bubble effects are caused by the vibration of the bubble coupled with the vibration of the cavity and, therefore, the measurement must be carefully prepared to prevent any air bubbles from entering the cavity.

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

Pegg, David T.

We extend and generalize previous work on the interference of light from independent cavities that began with the suggestion of Pfleegor and Mandel [Phys. Rev. 159, 1084 (1967)] that their observed interference of laser beams should not be associated too closely with particular states of the beams but more with the detection process itself. In particular we examine how the detection of interference induces a nonrandom-phase difference between internal cavity states with initial random phases for a much broader range of such states than has previously been considered. We find that a subsequent interference measurement should give results consistent withmore » the induced phase difference. The inclusion of more cavities in the interference measurements enables the construction in principle of a laboratory in the sense used by Aharonov and Susskind, made up of cavity fields that can serve as frames of phase reference. We also show reasonably simply how intrinsic phase coherence of a beam of light leaking from a single cavity arises for any internal cavity state, even a photon number state. Although the work presented here may have some implications for the current controversy over whether or not a typical laboratory laser produces a coherent state, it is not the purpose of this paper to enter this controversy; rather it is to examine the interesting quantum physics that arises for cavities with more general internal states.« less

Cavity Ring-Down Absorption of O2 in Air as a Temperature Sensor for an Open and a Cryogenic Optical Cavity.

PubMed

Nyaupane, Parashu R; Perez-Delgado, Yasnahir; Camejo, David; Wright, Lesley M; Manzanares, Carlos E

2017-05-01

The A-band of oxygen has been measured at low resolution at temperatures between 90 K and 373 K using the phase shift cavity ring down (PS-CRD) technique. For temperatures between 90 K and 295 K, the PS-CRD technique presented here involves an optical cavity attached to a cryostat. The static cell and mirrors of the optical cavity are all inside a vacuum chamber at the same temperature of the cryostat. The temperature of the cell can be changed between 77 K and 295 K. For temperatures above 295 K, a hollow glass cylindrical tube without windows has been inserted inside an optical cavity to measure the temperature of air flowing through the tube. The cavity consists of two highly reflective mirrors which are mounted parallel to each other and separated by a distance of 93 cm. In this experiment, air is passed through a heated tube. The temperature of the air flowing through the tube is determined by measuring the intensity of the oxygen absorption as a function of the wavenumber. The A-band of oxygen is measured between 298 K and 373 K, with several air flow rates. To obtain the temperature, the energy of the lower rotational state for seven selected rotational transitions is linearly fitted to a logarithmic function that contains the relative intensity of the rotational transition, the initial and final rotational quantum numbers, and the energy of the transition. Accuracy of the temperature measurement is determined by comparing the calculated temperature from the spectra with the temperature obtained from a calibrated thermocouple inserted at the center of the tube. This flowing air temperature sensor will be used to measure the temperatures of cooling air at the input (cold air) and output (hot air) after cooling the blades of a laboratory gas turbine. The results could contribute to improvements in turbine blade cooling design.

Sound absorption and transmission through flexible micro-perforated panels backed by an air layer and a thin plate.

PubMed

Bravo, Teresa; Maury, Cédric; Pinhède, Cédric

2012-05-01

This paper describes theoretical and experimental investigations into the sound absorption and transmission properties of micro-perforated panels (MPP) backed by an air cavity and a thin plate. A fully coupled modal approach is proposed to calculate the absorption coefficient and the transmission loss of finite-sized micro-perforated panels-cavity-panel (MPPCP) partitions with conservative boundary conditions. It is validated against infinite partition models and experimental data. A practical methodology is proposed using collocated pressure-velocity sensors to evaluate in an anechoic environment the transmission and absorption properties of conventional MPPCPs. Results show under which conditions edge scattering effects should be accounted for at low frequencies. Coupled mode analysis is also performed and analytical approximations are derived from the resonance frequencies and mode shapes of a flexible MPPCP. It is found that the Helmholtz-type resonance frequency is deduced from the one associated to the rigidly backed MPPCP absorber shifted up by the mass-air mass resonance of the flexible non-perforated double-panel. Moreover, it is shown analytically and experimentally that the absorption mechanisms at the resonances are governed by a large air-frame relative velocity over the MPP surface, with either in-phase or out-of-phase relationships, depending on the MPPCP parameters.

A multichannel amplitude and relative-phase controller for active sound quality control

NASA Astrophysics Data System (ADS)

Mosquera-Sánchez, Jaime A.; Desmet, Wim; de Oliveira, Leopoldo P. R.

2017-05-01

The enhancement of the sound quality of periodic disturbances for a number of listeners within an enclosure often confronts difficulties given by cross-channel interferences, which arise from simultaneously profiling the primary sound at each error sensor. These interferences may deteriorate the original sound among each listener, which is an unacceptable result from the point of view of sound quality control. In this paper we provide experimental evidence on controlling both amplitude and relative-phase functions of stationary complex primary sounds for a number of listeners within a cavity, attaining amplifications of twice the original value, reductions on the order of 70 dB, and relative-phase shifts between ± π rad, still in a free-of-interference control scenario. To accomplish such burdensome control targets, we have designed a multichannel active sound profiling scheme that bases its operation on exchanging time-domain control signals among the control units during uptime. Provided the real parts of the eigenvalues of persistently excited control matrices are positive, the proposed multichannel array is able to counterbalance cross-channel interferences, while attaining demanding control targets. Moreover, regularization of unstable control matrices is not seen to prevent the proposed array to provide free-of-interference amplitude and relative-phase control, but the system performance is degraded, as a function of the amount of regularization needed. The assessment of Loudness and Roughness metrics on the controlled primary sound proves that the proposed distributed control scheme noticeably outperforms current techniques, since active amplitude- and/or relative-phase-based enhancement of the auditory qualities of a primary sound no longer implies in causing interferences among different positions. In this regard, experimental results also confirm the effectiveness of the proposed scheme on stably enhancing the sound qualities of periodic sounds for multiple listeners within a cavity.

Behavior of a Light Solid in a Rotating Horizontal Cylinder with Liquid Under Vibration

NASA Astrophysics Data System (ADS)

Karpunin, I. E.; Kozlova, A. N.; Kozlov, N. V.

2018-06-01

Dynamics of a cylindrical body in a rotating cavity is experimentally studied under transversal translational vibrations of the cavity rotation axis. Experiments are run at high rotation rate, when under the action of centrifugal force the body shifts to the rotation axis (the centrifuged state). In the absence of vibrations, the lagging rotation of the body is observed, due to the body radial shift from the axis of rotation caused by gravity. The body average rotation regime depends on the cavity rotation rate. The vibrations lead to the excitation of different regimes of body differential rotation (leading or lagging) associated with the excitation of its inertial oscillations. The dependence of the differential speed of the body rotation on the vibration frequency is investigated. The body dynamics has a complex character depending on the dimensionless vibration frequency. The analysis of body oscillation trajectory revealed that the body oscillatory motion consists of several modes, which contribute to the averaged dynamics of the body and the flows in the cavity.

Thermally stable surface-emitting tilted wave laser

NASA Astrophysics Data System (ADS)

Shchukin, V. A.; Ledentsov, N. N.; Kalosha, V. P.; Ledentsov, N.; Agustin, M.; Kropp, J. R.; Maximov, M. V.; Zubov, F. I.; Shernyakov, Yu. M.; Payusov, A. S.; Gordeev, N. Yu; Kulagina, M. M.; Zhukov, A. E.

2018-02-01

Novel lasing modes in a vertical-cavity surface-emitting laser (VCSEL)-type structure based on an antiwaveguding cavity are studied. Such a VCSEL cavity has an effective refractive index in the cavity region lower than the average index of the distributed Bragg reflectors (DBRs). Such device in a stripe geometry does not support in-plane waveguiding mode, and all modes with a high Q-factor are exclusively VCSEL-like modes with similar near field profile in the vertical direction. A GaAlAs-based VCSEL structure studied contains a resonant cavity with multiple GaInAs quantum wells as an active region. The VCSEL structure is processed as an edge-emitting laser with cleaved facets and top contact representing a non-alloyed metal grid. Rectangular-shaped 400x400 µm pieces are cleaved with perpendicular facets. The contact grid region has a total width of 70 μm. 7 μm-wide metal stripes serve as non-alloyed metal contact and form periodic rectangular openings having a size of 10x40 μm. Surface emission through the windows on top of the chip is measured at temperatures from 90 to 380 K. Three different types of modes are observed. The longest wavelength mode (mode A) is a VCSEL-like mode at 854 nm emitting normal to the surface with a full width at half maximum (FWHM) of the far field 10°. Accordingly the lasing wavelength demonstrates a thermal shift of the wavelength of 0.06 nm/K. Mode B is at shorter wavelengths of 840 nm at room temperature, emitting light at two symmetric lobes at tilt angles 40° with respect to the normal to the surface in the directions parallel to the stripe. The emission wavelength of this mode shifts at a rate 0.22 nm/K according to the GaAs bandgap shift. The angle of mode B with respect to the normal reduces as the wavelength approaches the vertical cavity etalon wavelength and this mode finally merges with the VCSEL mode. Mode B hops between different lateral modes of the VCSEL forming a dense spectrum due to significant longitudinal cavity length, and the thermal shift of its wavelength is governed by the shift of the gain spectrum. The most interesting observation is Mode C, which shifts at a rate 0.06 nm/K and has a spectral width of 1 nm. Mode C matches the wavelength of the critical angle for total internal reflection for light impinging from semiconductor chip on semiconductor/air interface and propagates essentially as an in-plane mode. According to modeling data we conclude that the lasing mode represents a coupled state between the TM-polarized surface-trapped optical mode and the VCSEL cavity mode. The resulting mode has an extended near field zone and low propagation losses. The intensity of the mode drastically enhances once is appears at resonance with Mode B. A clear threshold is revealed in the L-I curves of all modes and there is a strong competition of the lasing mechanisms once the gain maximum is scanned over the related wavelength range by temperature change.

On the tunneling time of ultracold atoms through a system of two mazer cavities.

PubMed

Badshah, Fazal; Ge, Guo-Qin; Irfan, Muhammad; Qamar, Sajid; Qamar, Shahid

2018-01-30

We study the resonant tunneling of ultraslow atoms through a system of high quality microwave cavities. We find that the phase tunneling time across the two coupled cavities exhibits more frequent resonances as compared to the single cavity interaction. The increased resonances are instrumental in the display of an alternate sub and superclassical character of the tunneling time along the momentum axis with increasing energies of the incident slow atoms. Here, the intercavity separation appears as an additional controlling parameter of the system that provides an efficient control of the superclassical behavior of the phase tunneling time. Further, we find that the phase time characteristics through two cavity system has the combined features of the tunneling through a double barrier and a double well arrangements.

Realizing a partial general quantum cloning machine with superconducting quantum-interference devices in a cavity QED

NASA Astrophysics Data System (ADS)

Fang, Bao-Long; Yang, Zhen; Ye, Liu

2009-05-01

We propose a scheme for implementing a partial general quantum cloning machine with superconducting quantum-interference devices coupled to a nonresonant cavity. By regulating the time parameters, our system can perform optimal symmetric (asymmetric) universal quantum cloning, optimal symmetric (asymmetric) phase-covariant cloning, and optimal symmetric economical phase-covariant cloning. In the scheme the cavity is only virtually excited, thus, the cavity decay is suppressed during the cloning operations.

Development of an X-Band 50 MW Multiple Beam Klystron

NASA Astrophysics Data System (ADS)

Song, Liqun; Ferguson, Patrick; Ives, R. Lawrence; Miram, George; Marsden, David; Mizuhara, Max

2003-12-01

Calabazas Creek Research, Inc. is developing an X-band 50 MW multiple beam klystron (MBK) on a DOE SBIR Phase II grant. The electrical design and preliminary mechanical design were completed on the Phase I. This MBK consists of eight discrete klystron circuits driven by eight electron beams located symmetrically on a circle with a radius of 6.3 cm. Each beam operates at 190 kV and 66 A. The eight beam electron gun is in development on a DOE SBIR Phase II grant. Each circuit consists of an input cavity, two gain cavities, three penultimate cavities, and a three cavity output circuit operating in the PI/2 mode. Ring resonators were initially proposed for the complete circuit; however, low beam — wave interaction resulted in the necessity to use discrete cavities for all eight circuits. The input cavities are coupled via hybrid waveguides to ensure constant drive power amplitude and phase. The output circuits can either be combined using compact waveguide twists driving a TE01 high power window or combined into a TM04 mode converter driving the same TE01 window. The gain and efficiency for a single circuit has been optimized using KLSC, a 2 1/2D large signal klystron code. Simulations for a single circuit predict an efficiency of 53% for a single output cavity and 55% for the three cavity output resonator. The total RF output power for this MBK is 55 MW. During the Phase II emphasis will be given to cost reduction techniques resulting in a robust — high efficient — long life high power amplifier.

Two-Column Aerosol Project: Aerosol Light Extinction Measurements Field Campaign Report

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

Dubey, Manvendra; Aiken, Allison; Berg, Larry

We deployed Aerodyne Research Inc.’s first Cavity Attenuated Phase Shift extinction (CAPS PMex) monitor (built by Aerodyne) that measures light extinction by using a visible-light-emitting diode (LED) as a light source, a sample cell incorporating two high-reflectivity mirrors centered at the wavelength of the LED, and a vacuum photodiode detector in Cape Cod in 2012/13 for the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility’s Two-Column Aerosol Project (TCAP). The efficacy of this instrument is based on the fact that aerosols are broadband scatterers and absorbers of light. The input LED is square-wave modulated and passedmore » through the sample cell that distorts it due to exponential decay by aerosol light absorption and scattering; this is measured at the detector. The amount of phase shift of the light at the detector is used to determine the light extinction. This extinction measurement provides an absolute value, requiring no calibration. The goal was to compare the CAPS performance with direct measurements of absorption with ARM’s baseline photoacoustic soot spectrometer (PASS-3) and nephelometer instruments to evaluate its performance.« less

Characteristics research on self-amplified distributed feedback fiber laser

NASA Astrophysics Data System (ADS)

Song, Zhiqiang; Qi, Haifeng; Guo, Jian; Wang, Chang; Peng, Gangding

2014-09-01

A distributed feedback (DFB) fiber laser with a ratio of the backward to forward output power of 1:100 was composed by a 45-mm-length asymmetrical phase-shifted fiber grating fabricated on the 50-mm erbium-doped photosensitive fiber. Forward output laser was amplified using a certain length of Nufern EDFL-980-Hp erbium-doped fiber to absorb the surplus pump power after the active phase-shifted fiber grating and get population inversion. By using OptiSystem software, the best fiber length of the EDFL to get the highest gain was simulated. In order to keep the amplified laser with the narrow line-width and low noise, a narrow-band light filter consisting of a fiber Bragg grating (FBG) with the same Bragg wavelength as the laser and an optical circulator was used to filter the amplified spontaneous emission (ASE) noise of the out-cavity erbium-doped fiber. The designed laser structure sufficiently utilized the pump power, and a DFB fiber laser with the 32.5-mW output power, 11.5-kHz line width, and -87-dB/Hz relative intensity noise (RIN) at 300 mW of 980 nm pump power was brought out.

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

NASA Astrophysics Data System (ADS)

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

2010-06-01

We present an advanced approach to describing low-power trains of bright picosecond optical dissipative solitary pulses with an internal frequency modulation in practically important case of exploiting semiconductor heterolaser operating in near-infrared range in the active mode-locking regime. In the chosen schematic arrangement, process of the active mode-locking is caused by a hybrid nonlinear cavity consisting of this heterolaser and an external rather long single-mode optical fiber exhibiting square-law dispersion, cubic Kerr nonlinearity, and small linear optical losses. Our analysis of shaping dissipative solitary pulses includes three principal contributions associated with the modulated gain, total optical losses, as well as with linear and nonlinear phase shifts. In fact, various trains of the non-interacting to one another optical dissipative solitons appear within simultaneous balance between the second-order dispersion and cubic-law Kerr nonlinearity as well as between active medium gain and linear optical losses in a hybrid cavity. Our specific approach makes possible taking the modulating signals providing non-conventional composite regimes of a multi-pulse active mode-locking. Within our model, a contribution of the appearing nonlinear Ginzburg-Landau operator to the parameters of dissipative solitary pulses is described via exploiting an approximate variational procedure involving the technique of trial functions.

Oscillatory mode transition for supersonic open cavity flows

NASA Astrophysics Data System (ADS)

Kumar, Mayank; Vaidyanathan, Aravind

2018-02-01

The transition in the primary oscillatory mode in an open cavity has been experimentally investigated and the associated characteristics in a Mach 1.71 flow has been analyzed. The length-to-depth (L/D) ratios of the rectangular cavities are varied from 1.67 to 3.33. Unsteady pressure measurement and flow visualization are employed to understand the transitional flow physics. Flow visualization revealed the change in oscillation pattern from longitudinal mode to transverse mode and is also characterized by the presence of two bow shocks at the trailing edge instead of one. The transition is found to occur between L/D 1.67 and 2, marked by a change in the feedback mechanism, resulting in a shift from the vortex circulation driven transverse feedback mode to the oscillating shear layer driven longitudinal feedback mode. Cavities oscillating in the transition mode exhibit multiple tones of comparable strength. Correlation analysis indicated the shift in the feedback mechanism. Wavelet analysis revealed the temporal behaviour of tones during transition. Tone switching is observed in deeper cavities and is attributed to the occurrence of two bow shocks as evident from the temporo-spectral characteristics of transition that affects the shear layer modal shape.

Cavity-induced artificial gauge field in a Bose-Hubbard ladder

NASA Astrophysics Data System (ADS)

Halati, Catalin-Mihai; Sheikhan, Ameneh; Kollath, Corinna

2017-12-01

We consider theoretically ultracold interacting bosonic atoms confined to quasi-one-dimensional ladder structures formed by optical lattices and coupled to the field of an optical cavity. The atoms can collect a spatial phase imprint during a cavity-assisted tunneling along a rung via Raman transitions employing a cavity mode and a transverse running wave pump beam. By adiabatic elimination of the cavity field we obtain an effective Hamiltonian for the bosonic atoms, with a self-consistency condition. Using the numerical density-matrix renormalization-group method, we obtain a rich steady-state diagram of self-organized steady states. Transitions between superfluid to Mott-insulating states occur, on top of which we can have Meissner, vortex liquid, and vortex lattice phases. Also a state that explicitly breaks the symmetry between the two legs of the ladder, namely, the biased-ladder phase, is dynamically stabilized. We investigate the influence that a trapping potential has on the stability of the self-organized phases.

Faithful state transfer between two-level systems via an actively cooled finite-temperature cavity

NASA Astrophysics Data System (ADS)

Sárkány, Lőrinc; Fortágh, József; Petrosyan, David

2018-03-01

We consider state transfer between two qubits—effective two-level systems represented by Rydberg atoms—via a common mode of a microwave cavity at finite temperature. We find that when both qubits have the same coupling strength to the cavity field, at large enough detuning from the cavity mode frequency, quantum interference between the transition paths makes the swap of the excitation between the qubits largely insensitive to the number of thermal photons in the cavity. When, however, the coupling strengths are different, the photon-number-dependent differential Stark shift of the transition frequencies precludes efficient transfer. Nevertheless, using an auxiliary cooling system to continuously extract the cavity photons, we can still achieve a high-fidelity state transfer between the qubits.

Coherent addition of high power broad-area laser diodes with a compact VBG V-shaped external Talbot cavity

DOE PAGES

Liu, Bo; Braiman, Yehuda

2018-02-06

In this paper, we introduced a compact V-shaped external Talbot cavity for phase locking of high power broad-area laser diodes. The length of compact cavity is ~25 mm. Near diffraction-limit coherent addition of 10 broad-area laser diodes indicated that high quality phase locking was achieved. We measured the near-field emission mode of each individual broad-area laser diode with different feedback, such as a volume Bragg grating and a high reflection mirror. Finally, we found out that the best result of phase locking broad-area laser diodes was achieved by the compact V-shaped external Talbot cavity with volume Bragg grating feedback.

Coherent addition of high power broad-area laser diodes with a compact VBG V-shaped external Talbot cavity

NASA Astrophysics Data System (ADS)

Liu, Bo; Braiman, Yehuda

2018-05-01

We introduced a compact V-shaped external Talbot cavity for phase locking of high power broad-area laser diodes. The length of compact cavity is ∼25 mm. Near diffraction-limit coherent addition of 10 broad-area laser diodes indicated that high quality phase locking was achieved. We measured the near-field emission mode of each individual broad-area laser diode with different feedback, such as a volume Bragg grating and a high reflection mirror. We found out that the best result of phase locking broad-area laser diodes was achieved by the compact V-shaped external Talbot cavity with volume Bragg grating feedback.

Coherent addition of high power broad-area laser diodes with a compact VBG V-shaped external Talbot cavity

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

Liu, Bo; Braiman, Yehuda

In this paper, we introduced a compact V-shaped external Talbot cavity for phase locking of high power broad-area laser diodes. The length of compact cavity is ~25 mm. Near diffraction-limit coherent addition of 10 broad-area laser diodes indicated that high quality phase locking was achieved. We measured the near-field emission mode of each individual broad-area laser diode with different feedback, such as a volume Bragg grating and a high reflection mirror. Finally, we found out that the best result of phase locking broad-area laser diodes was achieved by the compact V-shaped external Talbot cavity with volume Bragg grating feedback.

Absolute-length determination of a long-baseline Fabry-Perot cavity by means of resonating modulation sidebands.

PubMed

Araya, A; Telada, S; Tochikubo, K; Taniguchi, S; Takahashi, R; Kawabe, K; Tatsumi, D; Yamazaki, T; Kawamura, S; Miyoki, S; Moriwaki, S; Musha, M; Nagano, S; Fujimoto, M K; Horikoshi, K; Mio, N; Naito, Y; Takamori, A; Yamamoto, K

1999-05-01

A new method has been demonstrated for absolute-length measurements of a long-baseline Fabry-Perot cavity by use of phase-modulated light. This method is based on determination of a free spectral range (FSR) of the cavity from the frequency difference between a carrier and phase-modulation sidebands, both of which resonate in the cavity. Sensitive response of the Fabry-Perot cavity near resonant frequencies ensures accurate determination of the FSR and thus of the absolute length of the cavity. This method was applied to a 300-m Fabry-Perot cavity of the TAMA gravitational wave detector that is being developed at the National Astronomical Observatory, Tokyo. With a modulation frequency of approximately 12 MHz, we successfully determined the absolute cavity length with resolution of 1 microm (3 x 10(-9) in strain) and observed local ground strain variations of 6 x 10(-8).

Supermode-density-wave-polariton condensation with a Bose–Einstein condensate in a multimode cavity

PubMed Central

Kollár, Alicia J.; Papageorge, Alexander T.; Vaidya, Varun D.; Guo, Yudan; Keeling, Jonathan; Lev, Benjamin L.

2017-01-01

Phase transitions, where observable properties of a many-body system change discontinuously, can occur in both open and closed systems. By placing cold atoms in optical cavities and inducing strong coupling between light and excitations of the atoms, one can experimentally study phase transitions of open quantum systems. Here we observe and study a non-equilibrium phase transition, the condensation of supermode-density-wave polaritons. These polaritons are formed from a superposition of cavity photon eigenmodes (a supermode), coupled to atomic density waves of a quantum gas. As the cavity supports multiple photon spatial modes and because the light–matter coupling can be comparable to the energy splitting of these modes, the composition of the supermode polariton is changed by the light–matter coupling on condensation. By demonstrating the ability to observe and understand density-wave-polariton condensation in the few-mode-degenerate cavity regime, our results show the potential to study similar questions in fully multimode cavities. PMID:28211455

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

Fang Baolong; Department of Mathematics and Physics, Hefei University, Hefei 230022; Yang Zhen

We propose a scheme for implementing a partial general quantum cloning machine with superconducting quantum-interference devices coupled to a nonresonant cavity. By regulating the time parameters, our system can perform optimal symmetric (asymmetric) universal quantum cloning, optimal symmetric (asymmetric) phase-covariant cloning, and optimal symmetric economical phase-covariant cloning. In the scheme the cavity is only virtually excited, thus, the cavity decay is suppressed during the cloning operations.

Cavity Self-Stabilization and Enhancement of Laser Gyroscopes by (Coupled) Optical Resonators

NASA Technical Reports Server (NTRS)

Smith, David D.

2006-01-01

We analyze the effect of a highly dispersive element placed inside a modulated optical cavity on the frequency and amplitude of the modulation to determine the conditions for cavity self-stabilization and enhanced gyroscopic sensitivity. Hence, we model cavity rotation or instability by an arbitrary AM/FM modulation, and the dispersive element as a phase and amplitude filter. We find that anomalous dispersion may be used to self-stabilize a laser cavity, provided the magnitude of the group index of refraction is smaller than the phase index of refraction in the cavity. The optimal stabilization is found to occur when the group index is zero. Group indices with magnitudes larger than the phase index (both normal and anomalous dispersion) are found to enhance the sensitivity of a laser gyroscope to rotation. Furthermore, our results indicate that atomic media, even coherent superpositions in multilevel atoms, are not useful for these applications, because the amplitude and phase filters work against one another, i.e., decreasing the modulation frequency increases its amplitude and vice versa, with one exception: negative group indices whose magnitudes are larger than the phase index result in negative, but enhanced, beat frequencies. On the other hand, for optical resonators the dispersion reversal associated with critical coupling enables the amplitude and phase filters to work together under a greater variety of circumstances than for atomic media. We find that for single over-coupled resonators, or in the case of under-coupled coupled-resonator-induced absorption, the absorption and normal dispersion on-resonance increase the contrast and frequency of the beat-note, respectively, resulting in a substantial enhancement of the gyroscopic response. Moreover, for cavity self-stabilization, we propose the use of a variety of coupled-resonator induced transparency that is accompanied by anomalous dispersion.

Design of a high-power Nd:YAG Q-switched laser cavity

NASA Astrophysics Data System (ADS)

Singh, Ikbal; Kumar, Avinash; Nijhawan, O. P.

1995-06-01

An electro-optically Q-switched Nd:YAG laser resonator that uses two end prisms placed orthogonally perpendicular to each other has been designed. This configuration improves the stability of the resonator and does not alter the characteristics of the electro-optical Q switch. The outcoupling ratio of the cavity is optimized by a change in the azimuthal angle of a phase-matched Porro prism placed at one end of the cavity. The prism placed at the other end of the cavity is designed so that it introduces a phase change of Pi , regardless of its orientation and index of refraction, resulting in a more efficient and stable cavity.

Disorder-induced transparency in a one-dimensional waveguide side coupled with optical cavities

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

Zhang, Yongyou, E-mail: yyzhang@bit.edu.cn; Dong, Guangda; Zou, Bingsuo

2014-05-07

Disorder influence on photon transmission behavior is theoretically studied in a one-dimensional waveguide side coupled with a series of optical cavities. For this sake, we propose a concept of disorder-induced transparency appearing on the low-transmission spectral background. Two kinds of disorders, namely, disorders of optical cavity eigenfrequencies and relative phases in the waveguide side coupled with optical cavities are considered to show the disorder-induced transparency. They both can induce the optical transmission peaks on the low-transmission backgrounds. The statistical mean value of the transmission also increases with increasing the disorders of the cavity eigenfrequencies and relative phases.

Ultra-High Aggregate Bandwidth Two-Dimensional Multiple-Wavelength Diode Laser Arrays

DTIC Science & Technology

1994-04-09

surface temperature across the wafer during the growth of the cavity spacer region using the fact that the molecular beam epitaxy (MBE) growth of GaAs...substrate surface temperature across the wafer during the growth of the cavity spacer region. Using the fact that, during an molecular beam epitaxy (MBE...K. Bacher and J.S. Harris, "Periodically Induced Mode Shift in Vertical Cavity Fabry Perot Etalons Grown by Molecular Beam Epitaxy ," to be presented

Electrically tunable terahertz polarization converter based on overcoupled metal-isolator-metal metamaterials infiltrated with liquid crystals

NASA Astrophysics Data System (ADS)

Vasić, Borislav; Zografopoulos, Dimitrios C.; Isić, Goran; Beccherelli, Romeo; Gajić, Radoš

2017-03-01

Large birefringence and its electrical modulation by means of Fréedericksz transition makes nematic liquid crystals (LCs) a promising platform for tunable terahertz (THz) devices. The thickness of standard LC cells is in the order of the wavelength, requiring high driving voltages and allowing only a very slow modulation at THz frequencies. Here, we first present the concept of overcoupled metal-isolator-metal (MIM) cavities that allow for achieving simultaneously both very high phase difference between orthogonal electric field components and large reflectance. We then apply this concept to LC-infiltrated MIM-based metamaterials aiming at the design of electrically tunable THz polarization converters. The optimal operation in the overcoupled regime is provided by properly selecting the thickness of the LC cell. Instead of the LC natural birefringence, the polarization-dependent functionality stems from the optical anisotropy of ultrathin and deeply subwavelength MIM structures. The dynamic electro-optic control of the LC refractive index enables the spectral shift of the resonant mode and, consequently, the tuning of the phase difference between the two orthogonal field components. This tunability is further enhanced by the large confinement of the resonant electromagnetic fields within the MIM cavity. We show that for an appropriately chosen linearly polarized incident field, the polarization state of the reflected field at the target operation frequency can be continuously swept between the north and south pole of the Poincaré sphere. Using a rigorous Q-tensor model to simulate the LC electro-optic switching, we demonstrate that the enhanced light-matter interaction in the MIM resonant cavity allows the polarization converter to operate at driving voltages below 10 Volt and with millisecond switching times.

Electrically tunable terahertz polarization converter based on overcoupled metal-isolator-metal metamaterials infiltrated with liquid crystals.

PubMed

Vasić, Borislav; Zografopoulos, Dimitrios C; Isić, Goran; Beccherelli, Romeo; Gajić, Radoš

2017-03-24

Large birefringence and its electrical modulation by means of Fréedericksz transition makes nematic liquid crystals (LCs) a promising platform for tunable terahertz (THz) devices. The thickness of standard LC cells is in the order of the wavelength, requiring high driving voltages and allowing only a very slow modulation at THz frequencies. Here, we first present the concept of overcoupled metal-isolator-metal (MIM) cavities that allow for achieving simultaneously both very high phase difference between orthogonal electric field components and large reflectance. We then apply this concept to LC-infiltrated MIM-based metamaterials aiming at the design of electrically tunable THz polarization converters. The optimal operation in the overcoupled regime is provided by properly selecting the thickness of the LC cell. Instead of the LC natural birefringence, the polarization-dependent functionality stems from the optical anisotropy of ultrathin and deeply subwavelength MIM structures. The dynamic electro-optic control of the LC refractive index enables the spectral shift of the resonant mode and, consequently, the tuning of the phase difference between the two orthogonal field components. This tunability is further enhanced by the large confinement of the resonant electromagnetic fields within the MIM cavity. We show that for an appropriately chosen linearly polarized incident field, the polarization state of the reflected field at the target operation frequency can be continuously swept between the north and south pole of the Poincaré sphere. Using a rigorous Q-tensor model to simulate the LC electro-optic switching, we demonstrate that the enhanced light-matter interaction in the MIM resonant cavity allows the polarization converter to operate at driving voltages below 10 Volt and with millisecond switching times.

Designing new classes of high-power, high-brightness VECSELs

NASA Astrophysics Data System (ADS)

Moloney, J. V.; Zakharian, A. R.; Hader, J.; Koch, Stephan W.

2005-10-01

Optically-pumped vertical external cavity semiconductor lasers offer the exciting possibility of designing kW-class solid state lasers that provide significant advantages over their doped YAG, thin-disk YAG and fiber counterparts. The basic VECSEL/OPSL (optically-pumped semiconductor laser) structure consists of a very thin (approximately 6 micron thick) active mirror consisting of a DBR high-reflectivity stack followed by a multiple quantum well resonant periodic (RPG) structure. An external mirror (reflectivity typically between 94%-98%) provides conventional optical feedback to the active semiconductor mirror chip. The "cold" cavity needs to be designed to take into account the semiconductor sub-cavity resonance shift with temperature and, importantly, the more rapid shift of the semiconductor material gain peak with temperature. Thermal management proves critical in optimizing the device for serious power scaling. We will describe a closed-loop procedure that begins with a design of the semiconductor active epi structure. This feeds into the sub-cavity optimization, optical and thermal transport within the active structure and thermal transport though the various heat sinking elements. Novel schemes for power scaling beyond current record performances will be discussed.

Performance of an untethered micro-optical pressure sensor

NASA Astrophysics Data System (ADS)

Ioppolo, Tindaro; Manzo, Maurizio; Krueger, Paul

2012-11-01

We present analytical and computational studies of the performance of a novel untethered micro-optical pressure sensor for fluid dynamics measurements. In particular, resolution and dynamic range will be presented. The sensor concept is based on the whispering galley mode (WGM) shifts that are observed in micro-scale dielectric optical cavities. A micro-spherical optical cavity (liquid or solid) is embedded in a thin polymeric sheet. The applied external pressure perturbs the morphology of the optical cavity leading to a shift in its optical resonances. The optical sensors are interrogated remotely, by embedding quantum dots or fluorescent dye in the micro-optical cavity. This allows a free space coupling of excitation and monitoring of the optical modes without the need of optical fibers or other cabling. With appropriate excitation and monitoring equipment, the micro-scale sensors can be distributed over a surface (e.g., including flexible biological surfaces) to monitor the local pressure field. We acknowledge the financial support from the National Science Foundation through grant CBET-1133876 with Dr. Horst Henning Winter as the program director.

Four-Phase Dendritic Model for the Prediction of Macrosegregation, Shrinkage Cavity, and Porosity in a 55-Ton Ingot

NASA Astrophysics Data System (ADS)

Ge, Honghao; Ren, Fengli; Li, Jun; Han, Xiujun; Xia, Mingxu; Li, Jianguo

2017-03-01

A four-phase dendritic model was developed to predict the macrosegregation, shrinkage cavity, and porosity during solidification. In this four-phase dendritic model, some important factors, including dendritic structure for equiaxed crystals, melt convection, crystals sedimentation, nucleation, growth, and shrinkage of solidified phases, were taken into consideration. Furthermore, in this four-phase dendritic model, a modified shrinkage criterion was established to predict shrinkage porosity (microporosity) of a 55-ton industrial Fe-3.3 wt pct C ingot. The predicted macrosegregation pattern and shrinkage cavity shape are in a good agreement with experimental results. The shrinkage cavity has a significant effect on the formation of positive segregation in hot top region, which generally forms during the last stage of ingot casting. The dendritic equiaxed grains also play an important role on the formation of A-segregation. A three-dimensional laminar structure of A-segregation in industrial ingot was, for the first time, predicted by using a 3D case simulation.

Resonance frequency control of RF normal conducting cavity using gradient estimator of reflected power

NASA Astrophysics Data System (ADS)

Leewe, R.; Shahriari, Z.; Moallem, M.

2017-10-01

Control of the natural resonance frequency of an RF cavity is essential for accelerator structures due to their high cavity sensitivity to internal and external vibrations and the dependency of resonant frequency on temperature changes. Due to the relatively high radio frequencies involved (MHz to GHz), direct measurement of the resonant frequency for real-time control is not possible by using conventional microcontroller hardware. So far, all operational cavities are tuned using phase comparison techniques. The temperature dependent phase measurements render this technique labor and time intensive. To eliminate the phase measurement, reduce man hours and speed up cavity start up time, this paper presents a control theme that relies solely on the reflected power measurement. The control algorithm for the nonlinear system is developed through Lyapunov's method. The controller stabilizes the resonance frequency of the cavity using a nonlinear control algorithm in combination with a gradient estimation method. Experimental results of the proposed system on a test cavity show that the resonance frequency can be tuned to its optimum operating point while the start up time of a single cavity and the accompanied man hours are significantly decreased. A test result of the fully commissioned control system on one of TRIUMF's DTL tanks verifies its performance under real environmental conditions.

Wavelength tunable ultrafast fiber laser via reflective mirror with taper structure.

PubMed

Fang, Li; Huang, Chuyun; Liu, Ting; Gogneau, Noelle; Bourhis, Eric; Gierak, Jacques; Oudar, Jean-Louis

2016-12-20

Laser sources with a controllable flexible wavelength have found widespread applications in optical fiber communication, optical sensing, and microscopy. Here, we report a tunable mode-locked fiber laser using a graphene-based saturable absorber and a tapered mirror as an end mirror in the cavity. The phase layer in the mirror is precisely etched by focused ion beam (FIB) milling technology, and the resonant wavelength of the mirror shifts correspond to the different etch depths. By scanning the tapered mirror mechanically, the center wavelength of a mode-locked fiber laser can be continuously tuned from 1562 to 1532 nm, with a pulse width in the sub-ps level and repetition rate of 27 MHz.

Casimir-Polder shifts on quantum levitation states

NASA Astrophysics Data System (ADS)

Crépin, P.-P.; Dufour, G.; Guérout, R.; Lambrecht, A.; Reynaud, S.

2017-03-01

An ultracold atom above a horizontal mirror experiences quantum reflection from the attractive Casimir-Polder interaction, which holds it against gravity and leads to quantum levitation states. We analyze this system by using a Liouville transformation of the Schrödinger equation and a Langer coordinate adapted to problems with a classical turning point. Reflection on the Casimir-Polder attractive well is replaced by reflection on a repulsive wall, and the problem is then viewed as an ultracold atom trapped inside a cavity with gravity and Casimir-Polder potentials acting, respectively, as top and bottom mirrors. We calculate numerically Casimir-Polder shifts of the energies of the cavity resonances and propose an approximate treatment which is precise enough to discuss spectroscopy experiments aimed at tests of the weak-equivalence principle on antihydrogen. We also discuss the lifetimes by calculating complex energies associated with cavity resonances.

Proof-of-principle Experiment of a Ferroelectric Tuner for the 1.3 GHz Cavity

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

Choi,E.M.; Hahn, H.; Shchelkunov, S. V.

2009-01-01

A novel tuner has been developed by the Omega-P company to achieve fast control of the accelerator RF cavity frequency. The tuner is based on the ferroelectric property which has a variable dielectric constant as function of applied voltage. Tests using a Brookhaven National Laboratory (BNL) 1.3 GHz electron gun cavity have been carried out for a proof-of-principle experiment of the ferroelectric tuner. Two different methods were used to determine the frequency change achieved with the ferroelectric tuner (FT). The first method is based on a S11 measurement at the tuner port to find the reactive impedance change when themore » voltage is applied. The reactive impedance change then is used to estimate the cavity frequency shift. The second method is a direct S21 measurement of the frequency shift in the cavity with the tuner connected. The estimated frequency change from the reactive impedance measurement due to 5 kV is in the range between 3.2 kHz and 14 kHz, while 9 kHz is the result from the direct measurement. The two methods are in reasonable agreement. The detail description of the experiment and the analysis are discussed in the paper.« less

Optically thin hybrid cavity for terahertz photo-conductive detectors

DOE PAGES

Thompson, Robert J.; Siday, T.; Glass, S.; ...

2017-01-23

Here, the efficiency of photoconductive (PC) devices, including terahertz detectors, is constrained by the bulk optical constants of PC materials. Here, we show that optical absorption in a PC layer can be modified substantially within a hybrid cavity containing nanoantennas and a Distributed Bragg Reflector. We find that a hybrid cavity, consisting of a GaAs PC layer of just 50 nm, can be used to absorb >75% of incident photons by trapping the light within the cavity. We provide an intuitive model, which describes the dependence of the optimum operation wavelength on the cavity thickness. We also find that themore » nanoantenna size is a critical parameter, small variations of which lead to both wavelength shifting and reduced absorption in the cavity, suggesting that impedance matching is key for achieving efficient absorption in the optically thin hybrid cavities.« less

Impacts of PM concentrations on visibility impairment

NASA Astrophysics Data System (ADS)

Jie, Guo; Wang, Mei-mei; Han, Ye-Xing; Yu, Zhi-Wei; Tang, Huai-Wu

2016-11-01

In the paper, an accurate and sensitive cavity attenuated phase shift spectroscopy (CAPS) sensor was used to monitor the atmospheric visibility. The CAPS system mainly includes a LED light source, a band-pass filter, an optical resonant cavity (composed of two high mirror, reflectivity is greater than 99.99%), a photoelectric detector and a lock-in amplifier. The 2L/min flow rate, the optical sensor rise and fall response time is about 15 s, so as to realize the fast measurement of visibility. An Allan variance analysis was carried out evaluating the optical system stability (and hence the maximum averaging time for the minimum detection limit) of the CAPS system. The minima ( 0.1 Mm-1) in the Allan plots show the optimum average time ( 100s) for optimum detection performance of the CAPS system. During this period, the extinction coefficient was correlated with PM2.5 mass (0.88), the extinction coefficient was correlated with PM10 mass (0.85). The atmospheric visibility was correlated with PM2.5 mass (0.74). The atmospheric visibility was correlated with PM10 mass (0.66).

Leupeptin reduces impulse noise induced hearing loss

PubMed Central

2011-01-01

Background Exposure to continuous and impulse noise can induce a hearing loss. Leupeptin is an inhibitor of the calpains, a family of calcium-activated proteases which promote cell death. The objective of this study is to assess whether Leupeptin could reduce the hearing loss resulting from rifle impulse noise. Methods A polyethelene tube was implanted into middle ear cavities of eight fat sand rats (16 ears). Following determination of auditory nerve brainstem evoked response (ABR) threshold in each ear, the animals were exposed to the noise of 10 M16 rifle shots. Immediately after the exposure, saline was then applied to one (control) ear and non-toxic concentrations of leupeptin determined in the first phase of the study were applied to the other ear, for four consecutive days. Results Eight days after the exposure, the threshold shift (ABR) in the control ears was significantly greater (44 dB) than in the leupeptin ears (27 dB). Conclusion Leupeptin applied to the middle ear cavity can reduce the hearing loss resulting from exposure to impulse noise. PMID:22206578

Absence of Vacuum Induced Berry Phases without the Rotating Wave Approximation in Cavity QED

NASA Astrophysics Data System (ADS)

Larson, Jonas

2012-01-01

We revisit earlier studies on Berry phases suggested to appear in certain cavity QED settings. It has been especially argued that a nontrivial geometric phase is achievable even in the situation of no cavity photons. We, however, show that such results hinge on imposing the rotating wave approximation (RWA), while without the RWA no Berry phases occur in these schemes. A geometrical interpretation of our results is obtained by introducing semiclassical energy surfaces which in a simple way brings out the phase-space dynamics. With the RWA, a conical intersection between the surfaces emerges and encircling it gives rise to the Berry phase. Without the RWA, the conical intersection is absent and therefore the Berry phase vanishes. It is believed that this is a first example showing how the application of the RWA in the Jaynes-Cummings model may lead to false conclusions, regardless of the mutual strengths between the system parameters.

Analysis of the tunable asymmetric fiber F-P cavity for fiber strain sensor edge-filter demodulation

NASA Astrophysics Data System (ADS)

Chen, Haotao; Liang, Youcheng

2014-12-01

An asymmetric fiber (Fabry-Pérot, F-P) interferometric cavity with the good linearity and wide dynamic range was successfully designed based on the optical thin film characteristic matrix theory; by adjusting the material of two different thin metallic layers, the asymmetric fiber F-P interferometric cavity was fabricated by depositing the multi-layer thin films on the optical fiber's end face. The asymmetric F-P cavity has the extensive potential application. In this paper, the demodulation method for the wavelength shift of the fiber Bragg grating (FBG) sensor based on the F-P cavity is demonstrated, and a theoretical formula is obtained. And the experimental results coincide well with the computational results obtained from the theoretical model.

A new source process for evolving repetitious earthquakes at Ngauruhoe volcano, New Zealand

NASA Astrophysics Data System (ADS)

Jolly, A. D.; Neuberg, J.; Jousset, P.; Sherburn, S.

2012-02-01

Since early 2005, Ngauruhoe volcano has produced repeating low-frequency earthquakes with evolving waveforms and spectral features which become progressively enriched in higher frequency energy during the period 2005 to 2009, with the trend reversing after that time. The earthquakes also show a seasonal cycle since January 2006, with peak numbers of events occurring in the spring and summer period and lower numbers of events at other times. We explain these patterns by the excitation of a shallow two-phase water/gas or water/steam cavity having temporal variations in volume fraction of bubbles. Such variations in two-phase systems are known to produce a large range of acoustic velocities (2-300 m/s) and corresponding changes in impedance contrast. We suggest that an increasing bubble volume fraction is caused by progressive heating of melt water in the resonant cavity system which, in turn, promotes the scattering excitation of higher frequencies, explaining both spectral shift and seasonal dependence. We have conducted a constrained waveform inversion and grid search for moment, position and source geometry for the onset of two example earthquakes occurring 17 and 19 January 2008, a time when events showed a frequency enrichment episode occurring over a period of a few days. The inversion and associated error analysis, in conjunction with an earthquake phase analysis show that the two earthquakes represent an excitation of a single source position and geometry. The observed spectral changes from a stationary earthquake source and geometry suggest that an evolution in both near source resonance and scattering is occurring over periods from days to months.

Analysis of the tunable asymmetric fiber F-P cavity for fiber sensor edge-filter demodulation

NASA Astrophysics Data System (ADS)

Chen, Haitao; Liang, Youcheng

2014-12-01

An asymmetric fiber (Fabry-Pérot,F-P) interferometric cavity with good linearity and wide dynamic range is successfully designed basing on optical thin film characteristic matrix theory; by choosing the material of two different thin metallic layers, the asymmetric fiber F-P interferometric cavity is fabricated by depositing the multi-layer thin films on the optical fiber's end face. The demodulation method for the wavelength shift of fiber Bragg grating (FBG) sensor basing on the F-P cavity is demonstrated and a theoretical formula is obtained. And the experimental results coincide well with computational results obtained from the theoretical model.

Study of phase-locked diode laser array and DFB/DBR surface emitting laser diode

NASA Astrophysics Data System (ADS)

Hsin, Wei

New types of phased-array and surface-emitting lasers are designed. The importance and approaches (or structures) of different phased array and surface emitting laser diodes are reviewed. The following are described: (1) a large optical cavity channel substrate planar laser array with layer thickness chirping; (2) a vertical cavity surface emitter with distributed feedback (DFB) optical cavity and a transverse junction buried heterostructure; (3) a microcavity distributed Bragg reflector (DBR) surface emitter; and (4) two surface emitting laser structures which utilized lateral current injection schemes to overcome the problems occurring in the vertical injection scheme.

Microwave measurement of the mass of frozen hydrogen pellets

DOEpatents

Talanker, Vera; Greenwald, Martin

1990-01-01

A nondestructive apparatus and method for measuring the mass of a moving object, based on the perturbation of the dielectric character of a resonant microwave cavity caused by the object passing through the cavity. An oscillator circuit is formed with a resonant cavity in a positive feedback loop of a microwave power amplifier. The moving object perturbs the resonant characteristics of the cavity causing a shift in the operating frequency of the oscillator proportional to the ratio of the pellet volume to the volume of the cavity. Signals from the cavity oscillation are mixed with a local oscillator. Then the IF frequency from the mixer is measured thereby providing a direct measurement of pellet mass based upon known physical properties and relationships. This apparatus and method is particularly adapted for the measurement of frozen hydrogen pellets.

Tandem resonator reflectance modulator

DOEpatents

Fritz, I.J.; Wendt, J.R.

1994-09-06

A wide band optical modulator is grown on a substrate as tandem Fabry-Perot resonators including three mirrors spaced by two cavities. The absorption of one cavity is changed relative to the absorption of the other cavity by an applied electric field, to cause a change in total reflected light, as light reflecting from the outer mirrors is in phase and light reflecting from the inner mirror is out of phase with light from the outer mirrors. 8 figs.

Cavity Attenuated Phase Shift (CAPS) Method for Airborne Aerosol Light Extinction Measurement: Instrument Validation and First Results from Field Deployment

NASA Astrophysics Data System (ADS)

Petzold, A.; Perim de Faria, J.; Berg, M.; Bundke, U.; Freedman, A.

2015-12-01

Monitoring the direct impact of aerosol particles on climate requires the continuous measurement of aerosol optical parameters like the aerosol extinction coefficient on a regular basis. Remote sensing and ground-based networks are well in place (e.g., AERONET, ACTRIS), whereas the regular in situ measurement of vertical profiles of atmospheric aerosol optical properties remains still an important challenge in quantifying climate change. The European Research Infrastructure IAGOS (In-service Aircraft for a Global Observing System; www.iagos.org) responds to the increasing requests for long-term, routine in situ observational data by using commercial passenger aircraft as measurement platform. However, scientific instrumentation for the measurement of atmospheric constituents requires major modifications before being deployable aboard in-service passenger aircraft. Recently, a compact and robust family of optical instruments based on the cavity attenuated phase shift (CAPS) technique has become available for measuring aerosol light extinction. While this technique was successfully deployed for ground-based atmospheric measurements under various conditions, its suitability for operation aboard aircraft in the free and upper free troposphere still has to be demonstrated. In this work, the modifications of a CAPS PMex instrument for measuring aerosol light extinction on aircraft, the results from subsequent laboratory tests for evaluating the modified instrument prototype, and first results from a field deployment aboard a research aircraft will be covered. In laboratory studies, the instrument showed excellent agreement (deviation < 5%) with theoretical values calculated from Rayleigh scattering cross-sections, when operated on pressurized air and CO2 at ambient and low pressure (~200 hPa). For monodisperse and polydisperse aerosols, reference aerosol extinction coefficients were calculated from measured size distributions and agreed with the CAPS PMex instrument response within 10% deviation. During the field deployment, aerosol extinction coefficients and associated aerosol size distributions have been measured and will be presented as comparison studies between measured and calculated data.

Nanofriction in Cavity Quantum Electrodynamics

NASA Astrophysics Data System (ADS)

Fogarty, T.; Cormick, C.; Landa, H.; Stojanović, Vladimir M.; Demler, E.; Morigi, Giovanna

2015-12-01

The dynamics of cold trapped ions in a high-finesse resonator results from the interplay between the long-range Coulomb repulsion and the cavity-induced interactions. The latter are due to multiple scatterings of laser photons inside the cavity and become relevant when the laser pump is sufficiently strong to overcome photon decay. We study the stationary states of ions coupled with a mode of a standing-wave cavity as a function of the cavity and laser parameters, when the typical length scales of the two self-organizing processes, Coulomb crystallization and photon-mediated interactions, are incommensurate. The dynamics are frustrated and in specific limiting cases can be cast in terms of the Frenkel-Kontorova model, which reproduces features of friction in one dimension. We numerically recover the sliding and pinned phases. For strong cavity nonlinearities, they are in general separated by bistable regions where superlubric and stick-slip dynamics coexist. The cavity, moreover, acts as a thermal reservoir and can cool the chain vibrations to temperatures controlled by the cavity parameters and by the ions' phase. These features are imprinted in the radiation emitted by the cavity, which is readily measurable in state-of-the-art setups of cavity quantum electrodynamics.

A Generalized Multi-Phase Framework for Modeling Cavitation in Cryogenic Fluids

NASA Technical Reports Server (NTRS)

Dorney, Dan (Technical Monitor); Hosangadi, Ashvin; Ahuja, Vineet

2003-01-01

A generalized multi-phase formulation for cavitation in fluids operating at temperatures elevated relative to their critical temperatures is presented. The thermal effects and the accompanying property variations due to phase change are modeled rigorously. Thermal equilibrium is assumed and fluid thermodynamic properties are specified along the saturation line using the NIST-12 databank. Fundamental changes in the physical characteristics of the cavity when thermal effects become pronounced are identified; the cavity becomes more porous, the interface less distinct, and has increased entrainment when temperature variations are present. Quantitative estimates of temperature and pressure depressions in both liquid nitrogen and liquid hydrogen were computed and compared with experimental data of Hord for hydrofoils. Excellent estimates of the leading edge temperature and pressure depression were obtained while the comparisons in the cavity closure region were reasonable. Liquid nitrogen cavities were consistently found to be in thermal equilibrium while liquid hydrogen cavities exhibited small, but distinct, non-equilibrium effects.

Commissioning of the 112 MHz SRF Gun and 500 MHz bunching cavities for the CeC PoP Linac

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

Belomestnykh, S.; Ben-Zvi, I.; Brutus, J. C.

The Coherent electron Cooling Proof-of-Principle (CeC PoP) experiment at BNL includes a short electron linac. During Phase 1, a 112 MHz superconducting RF photo-emission gun and two 500 MHz normal conducting bunching cavities were installed and are under commissioning. The paper describes the Phase1 linac layout and presents commissioning results for the cavities and associated RF, cryogenic and other sub-systems

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

DOEpatents

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

2001-01-01

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

Observation of laser formation inside a laser cavity containing a phase conjugate mirror

NASA Astrophysics Data System (ADS)

Wu, Frank F.

2012-03-01

Adaptive optics (AO) systems are used to compensate atmospheric perturbations on a propagating laser beam. However, AO needs a beacon to obtain the phase information. This paper presents a possible formation of beacon in target-in-theloop (TIL) geometry which is analog to a laser cavity. The TIL laser cavity is formed with a high reflectivity mirror on one end and an optical phase conjugate mirror as the second mirror. The TIL laser is initialized by a single frequency 10 ns Q-switched laser pulse. This is very similar to how an injection seeding or regenerative amplifier scheme starts a laser oscillation. With a cavity length of around 11 meters and an initial laser pulse of 10 ns, we have been able to isolate laser field images related to each round-trip pulse. Furthermore, by replacing the first mirror with a rough-surface target to simulate an uncooperative target and adding phase distortion elements to simulate atmospheric effects, we can observe the image status under such conditions.

Real-time observation of fluctuations in a driven-dissipative quantum many-body system undergoing a phase transition

NASA Astrophysics Data System (ADS)

Donner, Tobias

2015-03-01

A Bose-Einstein condensate whose motional degrees of freedom are coupled to a high-finesse optical cavity via a transverse pump beam constitutes a dissipative quantum many-body system with long range interactions. These interactions can induce a structural phase transition from a flat to a density-modulated state. The transverse pump field simultaneously represents a probe of the atomic density via cavity- enhanced Bragg scattering. By spectrally analyzing the light field leaking out of the cavity, we measure non-destructively the dynamic structure factor of the fluctuating atomic density while the system undergoes the phase transition. An observed asymmetry in the dynamic structure factor is attributed to the coupling to dissipative baths. Critical exponents for both sides of the phase transition can be extracted from the data. We further discuss our progress in adding strong short-range interactions to this system, in order to explore Bose-Hubbard physics with cavity-mediated long-range interactions and self-organization in lower dimensions.

Effects of mode profile on tunneling and traversal of ultracold atoms through vacuum-induced potentials

NASA Astrophysics Data System (ADS)

Badshah, Fazal; Irfan, Muhammad; Qamar, Sajid; Qamar, Shahid

2016-04-01

We consider the resonant interaction of an ultracold two-level atom with an electromagnetic field inside a high-Q micromaser cavity. In particular, we study the tunneling and traversal of ultracold atoms through vacuum-induced potentials for secant hyperbolic square and sinusoidal cavity mode functions. The phase time which may be considered as an appropriate measure of the time required for the atoms to cross the cavity, significantly modifies with the change of cavity mode profile. For example, switching between the sub and superclassical behaviors in phase time can occur due to the mode function. Similarly, negative phase time appears for the transmission of the two-level atoms in both excited and ground states for secant hyperbolic square mode function which is in contrast to the mesa mode case.

Single-drop impingement onto a wavy liquid film and description of the asymmetrical cavity dynamics

NASA Astrophysics Data System (ADS)

van Hinsberg, Nils Paul; Charbonneau-Grandmaison, Marie

2015-07-01

The present paper is devoted to an experimental investigation of the cavity formed upon a single-drop impingement onto a traveling solitary surface wave on a deep pool of the same liquid. The dynamics of the cavity throughout its complete expansion and receding phase are analyzed using high-speed shadowgraphy and compared to the outcomes of drop impingements onto steady liquid surface films having equal thickness. The effects of the surface wave velocity, amplitude and phase, drop impingement velocity, and liquid viscosity on the cavity's diameter and depth evolution are accurately characterized at various time instants. The wave velocity induces a distinct and in time increasing inclination of the cavity in the wave propagation direction. In particular for strong waves an asymmetrical distribution of the radial expansion and retraction velocity along the cavity's circumference is observed. A linear dependency between the absolute Weber number and the typical length and time scales associated with the cavity's maximum depth and maximum diameter is reported.

Sharp phase variations from the plasmon mode causing the Rabi-analogue splitting

NASA Astrophysics Data System (ADS)

Wang, Yujia; Sun, Chengwei; Gan, Fengyuan; Li, Hongyun; Gong, Qihuang; Chen, Jianjun

2017-06-01

The Rabi-analogue splitting in nanostructures resulting from the strong coupling of different resonant modes is of importance for lasing, sensing, switching, modulating, and quantum information processes. To give a clearer physical picture, the phase analysis instead of the strong coupling is provided to explain the Rabi-analogue splitting in the Fabry-Pérot (FP) cavity, of which one end mirror is a metallic nanohole array and the other is a thin metal film. The phase analysis is based on an analytic model of the FP cavity, in which the reflectance and the reflection phase of the end mirrors are dependent on the wavelength. It is found that the Rabi-analogue splitting originates from the sharp phase variation brought by the plasmon mode in the FP cavity. In the experiment, the Rabi-analogue splitting is realized in the plasmonic-photonic coupling system, and this splitting can be continually tuned by changing the length of the FP cavity. These experimental results agree well with the analytic and simulation data, strongly verifying the phase analysis based on the analytic model. The phase analysis presents a clear picture to understand the working mechanism of the Rabi-analogue splitting; thus, it may facilitate the design of the plasmonic-photonic and plasmonic-plasmonic coupling systems.

Liquid hydrogen densitometer utilizes open-ended microwave cavity

NASA Technical Reports Server (NTRS)

Smetana, J.; Wenger, N. C.

1967-01-01

Open-ended microwave cavity directly measures the density of flowing liquid, gaseous, or two-phase hydrogen. Its operation is based on derived relations between the cavity resonant frequency and the dielectric constant and density of hydrogen.

Nanophotonic sensors for oil sensing (Conference Presentation)

NASA Astrophysics Data System (ADS)

Salemink, Huub W.; Liu, Yazhao

2017-02-01

The proof of concept for a photonic cavity sensor for oil, water and gas detection is reported. The optical design employs an optimized photonic crystal cavity with fluidic infiltration of gas, water or (reservoir) oils. The 3D design and simulation is discussed, followed by the nanofabrication in standard silicon on insulator wafers (SoI). Using an optofluidic cicuit with PDMS channels, the fluid flow to the photonic cavity is controlled with syringe pumps. The variations in dielectric value (refractive index) change with the involved media result in a shift of the cavity resonant wavelength. For fluid change from water to typical oil (refractive index difference of 0.12), we report a wavelenght shift of up to 12 nm at the measurement wavelength of 1550 nm, in very good agreement with the simulations. We follow the optical response at a fixed wavelength, when feeding alternate flows or bubbles of oil/water through the optofluidic chip, and observe the flow pattern on camera. Finally we discuss the outlook and antifouling of the sensor with a special design. This work is supported by Shell Global Solutions. Appl.Phys.Lett., 106, 031116 (2015) J.Lightw.Technol., 33, 3672 (2015)

Measurement technology based on laser internal/external cavity tuning

NASA Astrophysics Data System (ADS)

Zhang, Shulian

2011-08-01

For an ordinary laser with two cavity mirrors, if the length of laser cavity changes half wavelength the laser frequency changes one longitudinal mode separation. For a laser with three cavity mirrors, in which a feedback mirror is used to feed part of the laser output beam back into the laser cavity, the external cavity length changes half wavelength the laser intensity fluctuates one period. This presentation gives some research results in measurement field based on changing (tuning) the length of laser internal/external cavity, including 1) HeNe laser cavity-tuning nanometer displacement measurement instruments (laser nanometer rulers), 2) HeNe laser feedback displacement measurement, 3) Nd:YAG laser feedback nanometer displacement measurement, 4) benchmark of waveplate phase retardation measurement based on laser frequency splitting, 5) in-site waveplate phase retardation measurement instruments based on laser feedback and polarization hopping, 6) quasi-common-path microchip Nd:YAG laser feedback interferometer, 7) non-contact Nd:YAG laser feedback surface profile measurement. Some of these instruments have been put into application and display some irreplaceable advantages.

First-principles calculations of niobium hydride formation in superconducting radio-frequency cavities

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

Ford, Denise C.; Cooley, Lance D.; Seidman, David N.

Niobium hydride is suspected to be a major contributor to degradation of the quality factor of niobium superconducting radio-frequency (SRF) cavities. In this study, we connect the fundamental properties of hydrogen in niobium to SRF cavity performance and processing. We modeled several of the niobium hydride phases relevant to SRF cavities and present their thermodynamic, electronic, and geometric properties determined from calculations based on density-functional theory. We find that the absorption of hydrogen from the gas phase into niobium is exothermic and hydrogen becomes somewhat anionic. The absorption of hydrogen by niobium lattice vacancies is strongly preferred over absorption intomore » interstitial sites. A single vacancy can accommodate six hydrogen atoms in the symmetrically equivalent lowest-energy sites and additional hydrogen in the nearby interstitial sites affected by the strain field: this indicates that a vacancy can serve as a nucleation center for hydride phase formation. Small hydride precipitates may then occur near lattice vacancies upon cooling. Vacancy clusters and extended defects should also be enriched in hydrogen, potentially resulting in extended hydride phase regions upon cooling. We also assess the phase changes in the niobium-hydrogen system based on charge transfer between niobium and hydrogen, the strain field associated with interstitial hydrogen, and the geometry of the hydride phases. The results of this study stress the importance of not only the hydrogen content in niobium, but also the recovery state of niobium for the performance of SRF cavities.« less

Field localization and enhancement of phase-locked second- and third-order harmonic generation in absorbing semiconductor cavities

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

Roppo, V.; Charles M. Bowden Research Facility, US Army RDECOM, Redstone Arsenal, Alabama 35803; Cojocaru, C.

We predict and experimentally observe the enhancement by three orders of magnitude of phase mismatched second and third harmonic generation in a GaAs cavity at 650 and 433 nm, respectively, well above the absorption edge. Phase locking between the pump and the harmonics changes the effective dispersion of the medium and inhibits absorption. Despite hostile conditions the harmonics resonate inside the cavity and become amplified leading to relatively large conversion efficiencies. Field localization thus plays a pivotal role despite the presence of absorption, and ushers in a new class of semiconductor-based devices in the visible and uv ranges.

Localization to delocalization crossover in a driven nonlinear cavity array

NASA Astrophysics Data System (ADS)

Brown, Oliver T.; Hartmann, Michael J.

2018-05-01

We study nonlinear cavity arrays where the particle relaxation rate in each cavity increases with the excitation number. We show that coherent parametric inputs can drive such arrays into states with commensurate filling that form non-equilibrium analogs of Mott insulating states. We explore the boundaries of the Mott insulating phase and the crossover to a delocalized phase with spontaneous first order coherence. While sharing many similarities with the Mott insulator to superfluid transition in equilibrium, the phase diagrams we find also show marked differences. Particularly the off diagonal order does not become long range since the influence of dephasing processes increases with increasing tunneling rates.

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

Webb, Aaron P.; Carlson, Charles T.; Weaver, William T.

A mask alignment system for providing precise and repeatable alignment between ion implantation masks and workpieces. The system includes a mask frame having a plurality of ion implantation masks loosely connected thereto. The mask frame is provided with a plurality of frame alignment cavities, and each mask is provided with a plurality of mask alignment cavities. The system further includes a platen for holding workpieces. The platen may be provided with a plurality of mask alignment pins and frame alignment pins configured to engage the mask alignment cavities and frame alignment cavities, respectively. The mask frame can be lowered ontomore » the platen, with the frame alignment cavities moving into registration with the frame alignment pins to provide rough alignment between the masks and workpieces. The mask alignment cavities are then moved into registration with the mask alignment pins, thereby shifting each individual mask into precise alignment with a respective workpiece.« less

Optical frequency-domain chromatic dispersion measurement method for higher-order modes in an optical fiber.

PubMed

Ahn, Tae-Jung; Jung, Yongmin; Oh, Kyunghwan; Kim, Dug Young

2005-12-12

We propose a new chromatic dispersion measurement method for the higher-order modes of an optical fiber using optical frequency modulated continuous-wave (FMCW) interferometry. An optical fiber which supports few excited modes was prepared for our experiments. Three different guiding modes of the fiber were identified by using far-field spatial beam profile measurements and confirmed with numerical mode analysis. By using the principle of a conventional FMWC interferometry with a tunable external cavity laser, we have demonstrated that the chromatic dispersion of a few-mode optical fiber can be obtained directly and quantitatively as well as qualitatively. We have also compared our measurement results with those of conventional modulation phase-shift method.

Cavitation in liquid cryogens. 2: Hydrofoil

NASA Technical Reports Server (NTRS)

Hord, J.

1973-01-01

Boundary layer principles, along with two-phase concepts, are used to improve existing correlative theory for developed cavity data. Details concerning cavity instrumentation, data analysis, correlative techniques, and experimental and theoretical aspects of a cavitating hydrofoil are given. Both desinent and thermodynamic data, using liquid hydrogen and liquid nitrogen, are reported. The thermodynamic data indicated that stable thermodynamic equilibrium exists throughout the vaporous cryogen cavities. The improved correlative formulas were used to evaluate these data. A new correlating parameter based on consideration of mass limiting two-phase flow flux across the cavity interface, is proposed. This correlating parameter appears attractive for future correlative and predictive applications. Agreement between theory and experiment is discussed, and directions for future analysis are suggested. The front half of the cavities, developed on the hydrofoil, may be considered as parabolically shaped.

Synthetic topological Kondo insulator in a pumped optical cavity

NASA Astrophysics Data System (ADS)

Zheng, Zhen; Zou, Xu-Bo; Guo, Guang-Can

2018-02-01

Motivated by experimental advances on ultracold atoms coupled to a pumped optical cavity, we propose a scheme for synthesizing and observing the Kondo insulator in Fermi gases trapped in optical lattices. The synthetic Kondo phase arises from the screening of localized atoms coupled to mobile ones, which in our proposal is generated via the pumping laser as well as the cavity. By designing the atom-cavity coupling, it can engineer a nearest-neighbor-site Kondo coupling that plays an essential role for supporting topological Kondo phase. Therefore, the cavity-induced Kondo transition is associated with a nontrivial topological features, resulting in the coexistence of the superradiant and topological Kondo state. Our proposal can be realized with current technique, and thus has potential applications in quantum simulation of the topological Kondo insulator in ultracold atoms.

Enhancement and inhibition of second-harmonic generation and absorption in a negative index cavity.

PubMed

de Ceglia, Domenico; D'Orazio, Antonella; De Sario, Marco; Petruzzelli, Vincenzo; Prudenzano, Francesco; Centini, Marco; Cappeddu, Mirko G; Bloemer, Mark J; Scalora, Michael

2007-02-01

We study second-harmonic generation in a negative-index material cavity. The transmission spectrum shows a bandgap between the electric and magnetic plasma frequencies. The nonlinear process is made efficient by local phase-matching conditions between a forward-propagating pump and a backward-propagating second-harmonic signal. By simultaneously exciting the cavity with counterpropagating pulses, and by varying their relative phase difference, one is able to enhance or inhibit linear absorption and the second-harmonic conversion efficiency.

The Effects of Laser Phase Noise on Laser Radar Performance

DTIC Science & Technology

1992-12-01

Laboratory 5. Figure 3 shows Allan variance plots of the above ultrastable C02 laser which has an open Fabry - Perot cavity 5. The open and solid circles...the same measurement time -r) by more than 10 dB. Therefore, the root Allan variance for the Fabry - Perot cavity ultrastable C02 laser can be...variance so that the SSB phase noise for the Fabry - Perot cavity ultrastable CO 2 laser is about 20 dB (because of the squaring operation) below that of the

Exploration of material removal rate of srf elliptical cavities as a function of media type and cavity shape on niobium and copper using centrifugal barrel polishing (cbp)

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

Palczewski, Ari; Ciovati, Gianluigi; Li, Yongming

Centrifugal barrel polishing (cbp) for SRF application is becoming more wide spread as the technique for cavity surface preparation. CBP is now being used in some form at SRF laboratories around the world including in the US, Europe and Asia. Before the process can become as mature as wet chemistry like eletro-polishing (EP) and buffered chemical polishing (BCP) there are many questions which remain unanswered. One of these topics includes the uniformity of removal as a function of cavity shape and material type. In this presentation we show CBP removal rates for various media types on 1.3 GHz TESLA andmore » 1.5 GHz CEBAF large/fine grain niobium cavities, and 1.3GHz low surface field copper cavity. The data will also include calculated RF frequency shift modeling non-uniform removal as a function of cavity position and comparing them with CBP results.« less

Cascaded-cavity Fabry-Perot interferometer for simultaneous measurement of temperature and strain with cross-sensitivity compensation

NASA Astrophysics Data System (ADS)

Tian, Jiajun; Jiao, Yuzhu; Ji, Shaobo; Dong, Xiaolong; Yao, Yong

2018-04-01

We propose and demonstrate a fiber sensor for simultaneous temperature and strain measurements. The proposed sensor is implemented by a cascaded-cavity Fabry-Perot (FP) fiber interferometer. The two cascaded FP cavities comprise a micro-air-cavity in a hollow-core tube fiber and a micro-silica-cavity in a standard single-mode fiber. To separate the interference spectrum of each FP cavity, the total spectrum is filtered in the frequency domain through band-pass filters, whose central frequencies were predesigned based on the relationship between the spatial frequency and free spectral range of each FP cavity. The different cross-sectional areas and thermal-optic coefficients of the two FP cavities confer different sensitivities to temperature and strain. Both parameters were measured simultaneously by tracking the wavelength shifts in the filtered interference spectra of the FP cavities. Moreover, the temperature-strain cross-sensitivity was compensated by solving a sensitivity-coefficient matrix equation for the two cavities, using the calibrated temperatures and strains. Other advantages of the proposed sensor are simple fabrication and an all-fiber structure. Owing to these properties, the proposed sensor is potentially applicable to real sensing applications.

Probing different regimes of strong field light-matter interaction with semiconductor quantum dots and few cavity photons

NASA Astrophysics Data System (ADS)

Hargart, F.; Roy-Choudhury, K.; John, T.; Portalupi, S. L.; Schneider, C.; Höfling, S.; Kamp, M.; Hughes, S.; Michler, P.

2016-12-01

In this work we present an extensive experimental and theoretical investigation of different regimes of strong field light-matter interaction for cavity-driven quantum dot (QD) cavity systems. The electric field enhancement inside a high-Q micropillar cavity facilitates exceptionally strong interaction with few cavity photons, enabling the simultaneous investigation for a wide range of QD-laser detuning. In case of a resonant drive, the formation of dressed states and a Mollow triplet sideband splitting of up to 45 μeV is measured for a mean cavity photon number < {n}c> ≤slant 1. In the asymptotic limit of the linear AC Stark effect we systematically investigate the power and detuning dependence of more than 400 QDs. Some QD-cavity systems exhibit an unexpected anomalous Stark shift, which can be explained by an extended dressed 4-level QD model. We provide a detailed analysis of the QD-cavity systems properties enabling this novel effect. The experimental results are successfully reproduced using a polaron master equation approach for the QD-cavity system, which includes the driving laser field, exciton-cavity and exciton-phonon interactions.

Effect of flow oscillations on cavity drag and a technique for their control

NASA Technical Reports Server (NTRS)

Gharib, M.; Roshko, A.; Sarohia, V.

1985-01-01

Experiments to relate the state of the shear layer to cavity drag have been performed in a water channel using a 4" axisymmetric cavity model. Detailed flow measurements in various cavity flow oscillation phases, amplitude amplification along the flow direction, distribution of shear stress, and other momentum flux obtained by laser Doppler velocimeter are presented. Measurements show exponential dependence of cavity drag on the length of the cavity. A jump in the cavity drag coefficient is observed as the cavity flow shows a bluff body wake type behavior. Natural and forced oscillations are introduced by a sinusoidally heated thin-film strip which excites the Tollmein-Schlichting waves in the boundary layer upstream of the gap. For a large gap, self-sustained periodic oscillations are observed, while for smaller gaps, which do not oscillate naturally, periodical oscillations can be obtained by external forcing through the strip heater. The drag of the cavity can be increased by one order of magnitude in the non-oscillating case through external forcing. Also, it is possible to completely eliminate mode switching by external forcing. For the first time, it is demonstrated that amplitude of cavity flow Kelvin-Helmholtz wave is dampened or cancelled by introduction of external perturbation of natural flow frequency but different phase.

JLEIC SRF cavity RF Design

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

Wang, Shaoheng; Guo, Jiquan; Wang, Haipeng

2016-05-01

The initial design of a low higher order modes (HOM) impedance superconducting RF (SRF) cavity is presented in this paper. The design of this SRF cavity is for the proposed Jefferson Lab Electron Ion Collider (JLEIC). The electron ring of JLEIC will operate with electrons of 3 to 10 GeV energy. The ion ring of JLEIC will operate with protons of up to 100 GeV energy. The bunch lengths in both rings are ~12 mm (RMS). In order to maintain the short bunch length in the ion ring, SRF cavities are adopted to provide large enough gradient. In the firstmore » phase of JLEIC, the PEP II RF cavities will be reused in the electron ring to lower the initial cost. The frequency of the SRF cavities is chosen to be the second harmonic of PEP II cavities, 952.6 MHz. In the second phase of JLEIC, the same frequency SRF cavities may replace the normal conducting PEP II cavities to achieve higher luminosity at high energy. At low energies, the synchro-tron radiation damping effect is quite weak, to avoid the coupled bunch instability caused by the intense closely-spaced electron bunches, low HOM impedance of the SRF cavities combined with longitudinal feedback sys-tem will be necessary.« less

Porous photonic crystal external cavity laser biosensor

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

Huang, Qinglan; Peh, Jessie; Hergenrother, Paul J.

2016-08-15

We report the design, fabrication, and testing of a photonic crystal (PC) biosensor structure that incorporates a porous high refractive index TiO{sub 2} dielectric film that enables immobilization of capture proteins within an enhanced surface-area volume that spatially overlaps with the regions of resonant electromagnetic fields where biomolecular binding can produce the greatest shifts in photonic crystal resonant wavelength. Despite the nanoscale porosity of the sensor structure, the PC slab exhibits narrowband and high efficiency resonant reflection, enabling the structure to serve as a wavelength-tunable element of an external cavity laser. In the context of sensing small molecule interactions withmore » much larger immobilized proteins, we demonstrate that the porous structure provides 3.7× larger biosensor signals than an equivalent nonporous structure, while the external cavity laser (ECL) detection method provides capability for sensing picometer-scale shifts in the PC resonant wavelength caused by small molecule binding. The porous ECL achieves a record high figure of merit for label-free optical biosensors.« less

A photon-photon quantum gate based on a single atom in an optical resonator.

PubMed

Hacker, Bastian; Welte, Stephan; Rempe, Gerhard; Ritter, Stephan

2016-08-11

That two photons pass each other undisturbed in free space is ideal for the faithful transmission of information, but prohibits an interaction between the photons. Such an interaction is, however, required for a plethora of applications in optical quantum information processing. The long-standing challenge here is to realize a deterministic photon-photon gate, that is, a mutually controlled logic operation on the quantum states of the photons. This requires an interaction so strong that each of the two photons can shift the other's phase by π radians. For polarization qubits, this amounts to the conditional flipping of one photon's polarization to an orthogonal state. So far, only probabilistic gates based on linear optics and photon detectors have been realized, because "no known or foreseen material has an optical nonlinearity strong enough to implement this conditional phase shift''. Meanwhile, tremendous progress in the development of quantum-nonlinear systems has opened up new possibilities for single-photon experiments. Platforms range from Rydberg blockade in atomic ensembles to single-atom cavity quantum electrodynamics. Applications such as single-photon switches and transistors, two-photon gateways, nondestructive photon detectors, photon routers and nonlinear phase shifters have been demonstrated, but none of them with the ideal information carriers: optical qubits in discriminable modes. Here we use the strong light-matter coupling provided by a single atom in a high-finesse optical resonator to realize the Duan-Kimble protocol of a universal controlled phase flip (π phase shift) photon-photon quantum gate. We achieve an average gate fidelity of (76.2 ± 3.6) per cent and specifically demonstrate the capability of conditional polarization flipping as well as entanglement generation between independent input photons. This photon-photon quantum gate is a universal quantum logic element, and therefore could perform most existing two-photon operations. The demonstrated feasibility of deterministic protocols for the optical processing of quantum information could lead to new applications in which photons are essential, especially long-distance quantum communication and scalable quantum computing.

Implementing two optimal economical quantum cloning with superconducting quantum interference devices in a cavity

NASA Astrophysics Data System (ADS)

Ye, Liu; Hu, GuiYu; Li, AiXia

2011-01-01

We propose a unified scheme to implement the optimal 1 → 3 economical phase-covariant quantum cloning and optimal 1 → 3 economical real state cloning with superconducting quantum interference devices (SQUIDs) in a cavity. During this process, no transfer of quantum information between the SQUIDs and cavity is required. The cavity field is only virtually excited. The scheme is insensitive to cavity decay. Therefore, the scheme can be experimentally realized in the range of current cavity QED techniques.

Status of the LCLS-II Accelerating Cavity Production

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

Daly, Ed; Marhauser, Frank; Fitzpatrick, Jarrod A.

Cavity serial production for the LCLS-II 4 GeV CM SRF linac has started. A quantity of 266 accelerating cavities has been ordered from two industrial vendors. Jefferson Laboratory leads the cavity procurement activities for the project and has successfully transferred the Nitrogen-Doping process to the industrial partners in the initial phase, which is now being applied for the production cavities. We report on the results from vendor qualification and the status of the cavity production for LCLS-II.

Effects of laser phase fluctuations on squeezing in intracavity second-harmonic generation

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

Kennedy, T. A. B.; Anderson, T. B.; Walls, D. F.

1989-08-01

Excellent squeezing in intracavity second-harmonic generation has been predicted to occur on cavity resonance in the output intensity fluctuations. Cavity detunings cause laser phase noise to couple in and reduce the squeezing observable. Here we consider the effects of laser phase fluctuations on the output-squeezing spectrum. Laser phase noise is modeled as an Ornstein-Uhlenbeck (colored-noise) Gaussian stochastic process and its effects are compared with the white-noise limit. This indicates that the white-noise model may qualitatively overestimate the deleterious effects of laser fluctuations on sideband squeezing. We compare our results with the recently reported experiment of Pereira /ital et/ /ital al/.more » (Phys. Rev. A 38, 4931 (1988)) and present an analysis of the empty cavity for comparison.« less

Realization of quantum gates with multiple control qubits or multiple target qubits in a cavity

NASA Astrophysics Data System (ADS)

Waseem, Muhammad; Irfan, Muhammad; Qamar, Shahid

2015-06-01

We propose a scheme to realize a three-qubit controlled phase gate and a multi-qubit controlled NOT gate of one qubit simultaneously controlling n-target qubits with a four-level quantum system in a cavity. The implementation time for multi-qubit controlled NOT gate is independent of the number of qubit. Three-qubit phase gate is generalized to n-qubit phase gate with multiple control qubits. The number of steps reduces linearly as compared to conventional gate decomposition method. Our scheme can be applied to various types of physical systems such as superconducting qubits coupled to a resonator and trapped atoms in a cavity. Our scheme does not require adjustment of level spacing during the gate implementation. We also show the implementation of Deutsch-Joza algorithm. Finally, we discuss the imperfections due to cavity decay and the possibility of physical implementation of our scheme.

Resonant photodetector for cavity- and phase-locking of squeezed state generation.

PubMed

Chen, Chaoyong; Li, Zhixiu; Jin, Xiaoli; Zheng, Yaohui

2016-10-01

Based on the requirement of squeezed state generation, we build the phase relationship between two electronic local oscillators for the cavity- and phase-locking branches, and a 2-way 90° power splitter is adopted to satisfy the phase relationship simultaneously, which greatly simplifies the experimental setup and adjusting process. A LC parallel resonant circuit, which is composed by the inherent capacitance of a photodiode and an extra inductor, is adopted in the resonant photodetector to improve the gain factor at the expected frequency. The gain of the resonant photodetector is about 30 dB higher than that of the broadband photodetector at the resonant frequency. The peak-to-peak value of the error signal for cavity-locking (phase-locking) with the resonant photodetector is 240 (260) times of that with the broadband photodetector, which can improve the locking performance on the premise of not affecting the squeezing degree.

Phase-locked array of quantum cascade lasers with an integrated Talbot cavity.

PubMed

Wang, Lei; Zhang, Jinchuan; Jia, Zhiwei; Zhao, Yue; Liu, Chuanwei; Liu, Yinghui; Zhai, Shenqiang; Ning, Zhuo; Xu, Xiangang; Liu, Fengqi

2016-12-26

We show a phase-locked array of three quantum cascade lasers with an integrated Talbot cavity at one side of the laser array. The coupling scheme is called diffraction coupling. By controlling the length of Talbot to be a quarter of Talbot distance (Z_t/4), in-phase mode operation can be selected. The in-phase operation shows great modal stability under different injection currents, from the threshold current to the full power current. The far-field radiation pattern of the in-phase operation contains three lobes, one central maximum lobe and two side lobes. The interval between adjacent lobes is about 10.5°. The output power is about 1.5 times that of a single-ridge laser. Further studies should be taken to achieve better beam performance and reduce optical losses brought by the integrated Talbot cavity.

Light shift effects in the Rb-87 maser

NASA Technical Reports Server (NTRS)

Busca, G.; Tetu, M.; Vanier, J.

1973-01-01

Previous work has shown the possibility to overcome the dependence of the Rb-87 maser frequency on light intensity by tuning the cavity at a proper setting. The conditions for this setting, called the light-independent frequency setting (LIFS), are carefully investigated. The results presented prove the existence of the LIFS and provide a new criterion for an automatic cavity tuning of the Rb maser.

Research on effects of phase error in phase-shifting interferometer

NASA Astrophysics Data System (ADS)

Wang, Hongjun; Wang, Zhao; Zhao, Hong; Tian, Ailing; Liu, Bingcai

2007-12-01

Referring to phase-shifting interferometry technology, the phase shifting error from the phase shifter is the main factor that directly affects the measurement accuracy of the phase shifting interferometer. In this paper, the resources and sorts of phase shifting error were introduction, and some methods to eliminate errors were mentioned. Based on the theory of phase shifting interferometry, the effects of phase shifting error were analyzed in detail. The Liquid Crystal Display (LCD) as a new shifter has advantage as that the phase shifting can be controlled digitally without any mechanical moving and rotating element. By changing coded image displayed on LCD, the phase shifting in measuring system was induced. LCD's phase modulation characteristic was analyzed in theory and tested. Based on Fourier transform, the effect model of phase error coming from LCD was established in four-step phase shifting interferometry. And the error range was obtained. In order to reduce error, a new error compensation algorithm was put forward. With this method, the error can be obtained by process interferogram. The interferogram can be compensated, and the measurement results can be obtained by four-step phase shifting interferogram. Theoretical analysis and simulation results demonstrate the feasibility of this approach to improve measurement accuracy.

Nonlinear Spectroscopy.

DTIC Science & Technology

1985-03-20

Finally, the (linear) .response of a Fabry - Perot cavity to a phase modulated light wave is considered because of its relevance to phase locking a laser...prepared and therefore doesn’t contribute. This effect provides the remaining factor of two. IV. FABRY - PEROT We now calculate the response of a plane...mirror Fabry - Perot cavity to a phase-modulated laser beam. This linear problem, which contrasts with the nonlinear atomic case, is the basis of an

Freezing Coherent Field Growth in a Cavity by the Quantum Zeno Effect

NASA Astrophysics Data System (ADS)

Bernu, J.; Deléglise, S.; Sayrin, C.; Kuhr, S.; Dotsenko, I.; Brune, M.; Raimond, J. M.; Haroche, S.

2008-10-01

We have frozen the coherent evolution of a field in a cavity by repeated measurements of its photon number. We use circular Rydberg atoms dispersively coupled to the cavity mode for an absorption-free photon counting. These measurements inhibit the growth of a field injected in the cavity by a classical source. This manifestation of the quantum Zeno effect illustrates the backaction of the photon number determination onto the field phase. The residual growth of the field can be seen as a random walk of its amplitude in the two-dimensional phase space. This experiment sheds light onto the measurement process and opens perspectives for active quantum feedback.

Nanoscale Biosensor Based on Silicon Photonic Cavity for Home Healthcare Diagnostic Application

NASA Astrophysics Data System (ADS)

Ebrahimy, Mehdi N.; Moghaddam, Aydin B.; Andalib, Alireza; Naziri, Mohammad; Ronagh, Nazli

2015-09-01

In this paper, a new ultra-compact optical biosensor based on photonic crystal (phc) resonant cavity is proposed. This sensor has ability to work in chemical optical processes for the determination and analysis of liquid material. Here, we used an optical filter based on two-dimensional phc resonant cavity on a silicon layer and an active area is created in center of cavity. According to results, with increasing the refractive index of cavity, resonant wavelengths shift so that this phenomenon provides the ability to measure the properties of materials. This novel designed biosensor has more advantage to operate in the biochemical process for example sensing protein and DNA molecule refractive index. This nanoscale biosensor has quality factor higher than 1.5 × 104 and it is suitable to be used in the home healthcare diagnostic applications.

Bunch shape monitor development in J-PARC linac

NASA Astrophysics Data System (ADS)

Miura, A.; Tamura, J.; Liu, Y.; Miyao, T.

2017-07-01

In the linac at the Japan accelerator research complex (J-PARC), we decided to use bunch shape monitors (BSMs) as phase-width monitors. Both centroid-phase set point at the frequency jump from SDTL (324 MHz) to ACS (972 MHz) and phase-width control are key issues for suppressing excess beam loss. BSM was designed and developed at the Institute for Nuclear Research, Russia. Because the BSM was first used between acceleration cavities, we need to improve it to protect it from the leakage-magnetic field of the quadrupole magnets and from outgassing impacts on the cavities. In this paper, we introduce these improvements to the BSM for the adoption of the location nearby the acceleration cavities.

DBR, Sub-wavelength grating, and Photonic crystal slab Fabry-Perot cavity design using phase analysis by FDTD.

PubMed

Kim, Jae Hwan Eric; Chrostowski, Lukas; Bisaillon, Eric; Plant, David V

2007-08-06

We demonstrate a Finite-Difference Time-Domain (FDTD) phase methodology to estimate resonant wavelengths in Fabry-Perot (FP) cavity structures. We validate the phase method in a conventional Vertical-Cavity Surface-Emitting Laser (VCSEL) structure using a transfer-matrix method, and compare results with a FDTD reflectance method. We extend this approach to a Sub-Wavelength Grating (SWG) and a Photonic Crystal (Phc) slab, either of which may replace one of the Distributed Bragg Reflectors (DBRs) in the VCSEL, and predict resonant conditions with varying lithographic parameters. Finally, we compare the resonant tunabilities of three different VCSEL structures, taking quality factors into account.

Rotary internal combustion engine with integrated supercharged fuel-air induction

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

Southard, A.A.

This patent describes an improved method of operating a rotary internal combustion engine of the type wherein a multicusped rotor rotatable upon a rotatable eccentric rotates within a cavity bounded by a wall of lobed trochoidal configuration. The rotor cusps have sealing engagement separating and defining operating chambers in the cavity about the rotor between adjacent pairs of cusps. Such chambers are angularly spaced about and orbit the center of the cavity as the rotor rotates while each chamber alternately expands and contracts in volume. The method comprises cylindrically operating each chamber through a sequence of six phases that aremore » synchronized with three successive increases and decreases in the volume of such chamber, with the first four phases being an internal combustion engine power cycle comprising an air intake phase, a compression phase, a combustion phase and an exhaust phase. The fifth phase comprises inducting air into the chamber, and the sixth phase comprises compressing the inducted air in such chamber and passing such inducted and compressed air through an elongated transfer zone.« less

A new look at a polar crown cavity as observed by SDO/AIA. Structure and dynamics

NASA Astrophysics Data System (ADS)

Régnier, S.; Walsh, R. W.; Alexander, C. E.

2011-09-01

Context. The Solar Dynamics Observatory (SDO) was launched in February 2010 and is now providing an unprecedented view of the solar activity at high spatial resolution and high cadence covering a broad range of temperature layers of the atmosphere. Aims: We aim at defining the structure of a polar crown cavity and describing its evolution during the erupting process. Methods: We use the high-cadence time series of SDO/AIA observations at 304 Å (50 000 K) and 171 Å (0.6 MK) to determine the structure of the polar crown cavity and its associated plasma, as well as the evolution of the cavity during the different phases of the eruption. We report on the observations recorded on 13 June 2010 located on the north-west limb. Results: We observe coronal plasma shaped by magnetic field lines with a negative curvature (U-shape) sitting at the bottom of a cavity. The cavity is located just above the polar crown filament material. We thus observe the inner part of the cavity above the filament as depicted in the classical three part coronal mass ejection (CME) model composed of a filament, a cavity, and a CME front. The filament (in this case a polar crown filament) is part of the cavity, and it makes a continuous structuring from the filament to the CME front depicted by concentric ellipses (in a 2D cartoon). Conclusions: We propose to define a polar crown cavity as a density depletion sitting above denser polar crown filament plasma drained down the cavity by gravity. As part of the polar crown filament, plasma at different temperatures (ranging from 50 000 K to 0.6 MK) is observed at the same location on the cavity dips and sustained by a competition between the gravity and the curvature of magnetic field lines. The eruption of the polar crown cavity as a solid body can be decomposed into two phases: a slow rise at a speed of 0.6 km s-1 and an acceleration phase at a mean speed of 25 km s-1. Two movies are only available at http://www.aanda.org

Single-longitudinal mode distributed-feedback fiber laser with low-threshold and high-efficiency

NASA Astrophysics Data System (ADS)

Jiang, Man; Zhou, Pu; Gu, Xijia

2018-01-01

Single-frequency fiber laser has attracted a lot of interest in recent years due to its numerous application potentials in telecommunications, LIDAR, high resolution sensing, atom frequency standard, etc. Phosphate glass fiber is one of the candidates for building compact high gain fiber lasers because of its capability of high-concentration of rare-earth ions doping in fiber core. Nevertheless, it is challenging for the integration of UV-written intra-core fiber Bragg gratings into the fiber laser cavity due to the low photosensitivity of phosphate glass fiber. The research presented in this paper will focus on demonstration of UV-written Bragg gratings in phosphate glass fiber and its application in direct-written short monolithic single-frequency fiber lasers. Strong π-phase shift Bragg grating structure is direct-inscribed into the Er/Yb co-doped gain fiber using an excimer laser, and a 5-cm-long phase mask is used to inscribe a laser cavity into the Er/Yb co-doped phosphate glass fibers. The phase mask is a uniform mask with a 50 μm gap in the middle. The fiber laser device emits output power of 10.44 mW with a slope efficiency of 21.5% and the threshold power is about 42.8 mW. Single-longitudinal mode operation is validated by radio frequency spectrum measurement. Moreover, the output spectrum at the highest power shows an excellent optical signal to noise ratio of about 70 dB. These results, to the best of our knowledge, show the lowest power threshold and highest efficiency among the reports that using the same structure to achieve single-longitudinal mode laser output.

Stationary bubble formation and cavity collapse in wedge-shaped hoppers

PubMed Central

Yagisawa, Yui; Then, Hui Zee; Okumura, Ko

2016-01-01

The hourglass is one of the apparatuses familiar to everyone, but reveals intriguing behaviors peculiar to granular materials, and many issues are remained to be explored. In this study, we examined the dynamics of falling sand in a special form of hourglass, i.e., a wedge-shaped hopper, when a suspended granular layer is stabilized to a certain degree. As a result, we found remarkably different dynamic regimes of bubbling and cavity. In the bubbling regime, bubbles of nearly equal size are created in the sand at a regular time interval. In the cavity regime, a cavity grows as sand beads fall before a sudden collapse of the cavity. Bubbling found here is quite visible to a level never discussed in the physics literature and the cavity regime is a novel phase, which is neither continuous, intermittent nor completely blocked phase. We elucidate the physical conditions necessary for the bubbling and cavity regimes and develop simple theories for the regimes to successfully explain the observed phenomena by considering the stability of a suspended granular layer and clogging of granular flow at the outlet of the hopper. The bubbling and cavity regimes could be useful for mixing a fluid with granular materials. PMID:27138747

Optical design and suspension system of the KAGRA output mode-cleaner

NASA Astrophysics Data System (ADS)

Kasuya, Junko; Winterflood, John; Li, Ju; Somiya, Kentaro

2018-02-01

KAGRA is a Japanese large scale, underground, cryogenic gravitational telescope which is under construction in the Kamioka mine. For using cryogenic test masses, the sensitivity of KAGRA is limited mainly by quantum noise. In order to reduce quantum noise, KAGRA employs an output mode-cleaner (OMC) at the output port that filters out junk light but allows the gravitational wave signal to go through. The requirement of the KAGRA OMC is even more challenging than other telescopes in the world since KAGRA plans to tune the signal readout phase so that the signal-to-noise ratio for our primary target source can be maximized. A proper selection of optical parameters and anti-vibration devices is required for the robust operation of the OMC. In this proceeding, we show our final results of modal-model simulations, in which we downselected the cavity length, the round-trip Gouy phase shift, the finesse, and the seismic isolation ratio for the suspended optics.

Spatial filter with volume gratings for high-peak-power multistage laser amplifiers

NASA Astrophysics Data System (ADS)

Tan, Yi-zhou; Yang, Yi-sheng; Zheng, Guang-wei; Shen, Ben-jian; Pan, Heng-yue; Liu, Li

2010-08-01

The regular spatial filters comprised of lens and pinhole are essential component in high power laser systems, such as lasers for inertial confinement fusion, nonlinear optical technology and directed-energy weapon. On the other hand the pinhole is treated as a bottleneck of high power laser due to harmful plasma created by the focusing beam. In this paper we present a spatial filter based on angular selectivity of Bragg diffraction grating to avoid the harmful focusing effect in the traditional pinhole filter. A spatial filter consisted of volume phase gratings in two-pass amplifier cavity were reported. Two-dimensional filter was proposed by using single Pi-phase-shifted Bragg grating, numerical simulation results shown that its angular spectrum bandwidth can be less than 160urad. The angular selectivity of photo-thermorefractive glass and RUGATE film filters, construction stability, thermal stability and the effects of misalignments of gratings on the diffraction efficiencies under high-pulse-energy laser operating condition are discussed.

Electrically-Tunable Group Delays Using Quantum Wells in a Distributed Bragg Reflector

NASA Technical Reports Server (NTRS)

Nelson, Thomas R., Jr.; Loehr, John P.; Fork, Richard L.; Cole, Spencer; Jones, Darryl K.; Keys, Andrew

1999-01-01

There is a growing interest in the fabrication of semiconductor optical group delay lines for the development of phased arrays of Vertical-Cavity Surface-Emitting Lasers (VCSELs). We present a novel structure incorporating In(x)GA(1-x)As quantum wells in the GaAs quarter-wave layers of a GaAs/AlAs distributed Bragg reflector (DBR). Application of an electric field across the quantum wells leads to red shifting and peak broadening of the el-hhl exciton peak via the quantum-confined Stark effect. Resultant changes in the index of refraction thereby provide a means for altering the group delay of an incident laser pulse. We discuss the tradeoffs between the maximum amount of change in group delay versus absorption losses for such a device. We also compare a simple theoretical model to experimental results, and discuss both angle and position tuning of the BDR band edge resonance relative to the exciton absorption peak. The advantages of such monolithically grown devices for phased-array VCSEL applications will be detailed.

Effects of surface diffusion on high temperature selective emitters

DOE PAGES

Peykov, Daniel; Yeng, Yi Xiang; Celanovic, Ivan; ...

2015-01-01

Using morphological and optical simulations of 1D tantalum photonic crystals at 1200K, surface diffusion was determined to gradually reduce the efficiency of selective emitters. This was attributed to shifting resonance peaks and declining emissivity caused by changes to the cavity dimensions and the aperture width. Decreasing the structure’s curvature through larger periods and smaller cavity widths, as well as generating smoother transitions in curvature through the introduction of rounded cavities, was found to alleviate this degradation. An optimized structure, that shows both high efficiency selective emissivity and resistance to surface diffusion, was presented.

Linear beam dynamics and ampere class superconducting RF cavities at RHIC

NASA Astrophysics Data System (ADS)

Calaga, Rama R.

The Relativistic Heavy Ion Collider (RHIC) is a hadron collider designed to collide a range of ions from protons to gold. RHIC operations began in 2000 and has successfully completed five physics runs with several species including gold, deuteron, copper, and polarized protons. Linear optics and coupling are fundamental issues affecting the collider performance. Measurement and correction of optics and coupling are important to maximize the luminosity and sustain stable operation. A numerical approach, first developed at SLAC, was implemented to measure linear optics from coherent betatron oscillations generated by ac dipoles and recorded at multiple beam position monitors (BPMs) distributed around the collider. The approach is extended to a fully coupled 2D case and equivalence relationships between Hamiltonian and matrix formalisms are derived. Detailed measurements of the transverse coupling terms are carried out at RHIC and correction strategies are applied to compensate coupling both locally and globally. A statistical approach to determine BPM reliability and performance over the past three runs and future improvements also discussed. Aiming at a ten-fold increase in the average heavy-ion luminosity, electron cooling is the enabling technology for the next luminosity upgrade (RHIC II). Cooling gold ion beams at 100 GeV/nucleon requires an electron beam of approximately 54 MeV and a high average current in the range of 50-200 mA. All existing e-Coolers are based on low energy DC accelerators. The only viable option to generate high current, high energy, low emittance CW electron beam is through a superconducting energy-recovery linac (SC-ERL). In this option, an electron beam from a superconducting injector gun is accelerated using a high gradient (˜ 20 MV/m) superconducting RF (SRF) cavity. The electrons are returned back to the cavity with a 180° phase shift to recover the energy back into the cavity before being dumped. A design and development of a half-cell electron gun and a five-cell SRF linac cavity are presented. Several RF and beam dynamics issues ultimately resulting in an optimum cavity design are discussed in detail.

Dynamics of shaping ultrashort optical dissipative solitary pulses in the actively mode-locked semiconductor laser with an external long-haul single-mode fiber cavity

NASA Astrophysics Data System (ADS)

Shcherbakov, Alexandre S.; Moreno Zarate, Pedro

2010-02-01

We describe the conditions of shaping regular trains of optical dissipative solitary pulses, excited by multi-pulse sequences of periodic modulating signals, in the actively mode-locked semiconductor laser heterostructure with an external long-haul single-mode silicon fiber exhibiting square-law dispersion, cubic Kerr nonlinearity, and linear optical losses. The presented model for the analysis includes three principal contributions associated with the modulated gain, optical losses, as well as linear and nonlinear phase shifts. In fact, the trains of optical dissipative solitary pulses appear within simultaneous presenting and a balance of mutually compensating interactions between the second-order dispersion and cubic-law Kerr nonlinearity as well as between active medium gain and linear optical losses in the combined cavity. Within such a model, a contribution of the nonlinear Ginzburg-Landau operator to shaping the parameters of optical dissipative solitary pulses is described via exploiting an approximate variational procedure involving the technique of trial functions. Finally, the results of the illustrating proof-of-principle experiments are briefly presented and discussed in terms of optical dissipative solitary pulses.

A high performance DAC /DDS daughter module for the RHIC LLRF platform

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

Hayes, T.; Harvey, M.; Narayan, G.

The RHIC LLRF upgrade is a flexible, modular system. Output signals are generated by a custom designed XMC card with 4 high speed digital to analog (DAC) converters interfaced to a high performance field programmable gate array (FPGA). This paper discusses the hardware details of the XMC DAC board as well as the implementation of a low noise rf synthesizer with digital IQ modulation. This synthesizer also provides injection phase cogging and frequency hop rebucketing capabilities. A new modular RHIC LLRF system was recently designed and commissioned based on custom designed XMC cards. As part of that effort a highmore » speed, four channel DAC board was designed. The board uses Maxim MAX5891 16 bit DACs with a maximum update rate of 600 Msps. Since this module is intended to be used for many different systems throughout the Collider Accelerator complex, it was designed to be as generic as possible. One major application of this DAC card is to implement digital synthesizers to provide drive signals to the various cavities at RHIC. Since RHIC is a storage ring with stores that typically last many hours, extremely low RF noise is a critical requirement. Synchrotron frequencies at RHIC range from a few hertz to several hundred hertz depending on the species and point in the acceleration cycle so close in phase noise is a major concern. The RHIC LLRF system uses the Update Link, a deterministic, high speed data link that broadcasts the revolution frequency and the synchronous phase angle. The digital synthesizers use this data to generate a properly phased analog drive signal. The synthesizers must also provide smooth phase shifts for cogging and support frequency shift rebucketing. One additional feature implemented in the FPGA is a digital waveform generator (WFG) that generates I and Q data pairs based on a user selected amplitude and phase profile as a function of time.« less

Doppler-broadened NICE-OHMS beyond the cavity-limited weak absorption condition - I. Theoretical description

NASA Astrophysics Data System (ADS)

Ma, Weiguang; Silander, Isak; Hausmaninger, Thomas; Axner, Ove

2016-01-01

Doppler-broadened (Db) noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS) is conventionally described by an expression (here referred to as the CONV expression) that is restricted to the case when the single-pass absorbance, α0L, is much smaller than the empty cavity losses, π/F [here termed the conventional cavity-limited weak absorption (CCLWA) condition]. This limits the applicability of the technique, primarily its dynamic range and calibration capability. To remedy this, this work derives extended descriptions of Db NICE-OHMS that are not restricted to the CCLWA condition. First, the general principles of Db NICE-OHMS are scrutinized in some detail. Based solely upon a set of general assumptions, predominantly that it is appropriate to linearize the Beer-Lambert law, that the light is modulated to a triplet, and that the Pound-Drever-Hall sidebands are fully reflected, a general description of Db NICE-OHMS that is not limited to any specific restriction on α0L vs. π/F, here referred to as the FULL description, is derived. However, this description constitutes a set of equations to which no closed form solution has been found. Hence, it needs to be solved numerically (by iterations), which is inconvenient. To circumvent this, for the cases when α0L<π/F but without the requirement that the stronger CCLWA condition needs to be fulfilled, a couple of simplified extended expressions that are expressible in closed analytical form, referred to as the extended locking and extended transmission description, ELET, and the extended locking and full transmission description, ELFT, have been derived. An analysis based on simulations validates the various descriptions and assesses to which extent they agree. It is shown that in the CCLWA limit, all extended descriptions revert to the CONV expression. The latter one deviates though from the extended ones for α0L around and above 0.1π/F. The two simplified extended descriptions agree with the FULL description for a larger range of α0 L than the CONV expression, viz. for the ELET description for α0L up to 0.3π/F and for ELFT for α0L up to 0.6 or 1.0 π/F (depending on the mode of detection). It is then demonstrated that the conventional view of Db NICE-OHMS, which states that the out-of-phase and the in-phase signals can be referred to as a pure absorption and dispersion signal, respectively, breaks down when the CCLWA condition does not hold. In this case, the out-of-phase signal is additionally affected by the phase shifts of the laser components (i.e. dispersion) while the in-phase signal is also influenced by their attenuation. Access to new descriptions broadens considerably the dynamic range of Db NICE-OHMS and facilitates calibration using standard references samples, and thereby its applicability.

CW laser pumped emerald laser

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

Shand, M.L.; Lai, S.T.

1984-02-01

A CW laser-pumped emerald laser is reported. A 34 percent output power slope efficiency is observed with longitudinal pumping by a krypton laser in a nearly concentric cavity. The laser has been tuned from 728.8 to 809.0 nm. Losses in emerald are larger than those of alexandrite determined in a similar cavity. The present data also indicate that the excited state absorption minimum is shifted from that of alexandrite. 13 references.

Diversified pulse generation from frequency shifted feedback Tm-doped fibre lasers.

PubMed

Chen, He; Chen, Sheng-Ping; Jiang, Zong-Fu; Hou, Jing

2016-05-19

Pulsed fibre lasers operating in the eye-safe 2 μm spectral region have numerous potential applications in areas such as remote sensing, medicine, mid-infrared frequency conversion, and free-space communication. Here, for the first time, we demonstrate versatile 2 μm ps-ns pulses generation from Tm-based fibre lasers based on frequency shifted feedback and provide a comprehensive report of their special behaviors. The lasers are featured with elegant construction and the unparalleled capacity of generating versatile pulses. The self-starting mode-locking is initiated by an intra-cavity acousto-optical frequency shifter. Diversified mode-locked pulse dynamics were observed by altering the pump power, intra-cavity polarization state and cavity structure, including as short as 8 ps single pulse sequence, pulse bundle state and up to 12 nJ, 3 ns nanosecond rectangular pulse. A reflective nonlinear optical loop mirror was introduced to successfully shorten the pulses from 24 ps to 8 ps. Beside the mode-locking operation, flexible Q-switching and Q-switched mode-locking operation can also be readily achieved in the same cavity. Up to 78 μJ high energy nanosecond pulse can be generated in this regime. Several intriguing pulse dynamics are characterized and discussed.

Design of a compact high-speed optical modulator based on a hybrid plasmonic nanobeam cavity

NASA Astrophysics Data System (ADS)

Javid, Mohammad Reza; Miri, Mehdi; Zarifkar, Abbas

2018-03-01

A hybrid plasmonic electro-optic modulator based on a polymer-filled one dimensional photonic crystal nanobeam (1D PhCNB) cavity is proposed here. In the proposed structure the optical intensity modulation is realized by shifting the resonant wavelength of the cavity through electrically tuning the refractive index of the electro-optic polymer in the hybrid plasmonic waveguide. As a result of the subwavelength light confinement in the hybrid plasmonic waveguide and the compact footprint of the 1D PhCNB cavity, the designed modulator has the small overall footprint of 3 . 6 μm2 and the required wavelength shift can be achieved by applying very small actuating power. Three dimensional finite-difference time-domain (3D-FDTD) simulations show that the modulation depth of 10.9 dB, and insertion loss of 1.14 dB, along with very high modulation speed of 224 GHz can be achieved in the proposed modulator with very low modulation energy of 0.75 fJ/bit. A comparison between the performance parameters of the proposed modulator and those of previously reported PhCNB based modulators reveals the superior performance of the proposed structure in terms of modulation speed, energy consumption and overall footprint.

Method and apparatus for varying accelerator beam output energy

DOEpatents

Young, Lloyd M.

1998-01-01

A coupled cavity accelerator (CCA) accelerates a charged particle beam with rf energy from a rf source. An input accelerating cavity receives the charged particle beam and an output accelerating cavity outputs the charged particle beam at an increased energy. Intermediate accelerating cavities connect the input and the output accelerating cavities to accelerate the charged particle beam. A plurality of tunable coupling cavities are arranged so that each one of the tunable coupling cavities respectively connect an adjacent pair of the input, output, and intermediate accelerating cavities to transfer the rf energy along the accelerating cavities. An output tunable coupling cavity can be detuned to variably change the phase of the rf energy reflected from the output coupling cavity so that regions of the accelerator can be selectively turned off when one of the intermediate tunable coupling cavities is also detuned.

The design of a simulated in-line side-coupled 6 MV linear accelerator waveguide.

PubMed

St Aubin, Joel; Steciw, Stephen; Fallone, B G

2010-02-01

The design of a 3D in-line side-coupled 6 MV linac waveguide for medical use is given, and the effect of the side-coupling and port irises on the radio frequency (RF), beam dynamics, and dosimetric solutions is examined. This work was motivated by our research on a linac-MR hybrid system, where accurate electron trajectory information for a clinical medical waveguide in the presence of an external magnetic field was needed. For this work, the design of the linac waveguide was generated using the finite element method. The design outlined here incorporates the necessary geometric changes needed to incorporate a full-end accelerating cavity with a single-coupling iris, a waveguide-cavity coupling port iris that allows power transfer into the waveguide from the magnetron, as well as a method to control the RF field magnitude within the first half accelerating cavity into which the electrons from the gun are injected. With the full waveguide designed to resonate at 2998.5 +/- 0.1 MHz, a full 3D RF field solution was obtained. The accuracy of the 3D RF field solution was estimated through a comparison of important linac parameters (Q factor, shunt impedance, transit time factor, and resonant frequency) calculated for one accelerating cavity with the benchmarked program SUPERFISH. It was found that the maximum difference between the 3D solution and SUPERFISH was less than 0.03%. The eigenvalue solver, which determines the resonant frequencies of the 3D side-coupled waveguide simulation, was shown to be highly accurate through a comparison with lumped circuit theory. Two different waveguide geometries were examined, one incorporating a 0.5 mm first side cavity shift and another with a 1.5 mm first side cavity shift. The asymmetrically placed side-coupling irises and the port iris for both models were shown to introduce asymmetries in the RF field large enough to cause a peak shift and skewing (center of gravity minus peak shift) of an initially cylindrically uniform electron beam accelerating within the waveguide. The shifting and skewing of the electron beam were found to be greatest due to the effects of the side-coupling irises on the RF field. A further Monte Carlo study showed that this effect translated into a 1% asymmetry in a 40 x 40 cm2 field dose profile. A full 3D design for an in-line side-coupled 6 MV linear accelerator that emulates a common commercial waveguide has been given. The effect of the side coupling on the dose distribution has been shown to create a slight asymmetry, but overall does not affect the clinical applicability of the linac. The 3D in-line side-coupled linac model further provides a tool for the investigation of linac performance within an external magnetic field, which exists in an integrated linac-MR system.

Phase I/II Study of Postoperative Adjuvant Chemoradiation for Advanced-Stage Cutaneous Squamous Cell Carcinoma of the Head and Neck (cSCCHN)

ClinicalTrials.gov

2014-11-17

Recurrent Skin Cancer; Recurrent Squamous Cell Carcinoma of the Lip and Oral Cavity; Squamous Cell Carcinoma of the Skin; Stage III Squamous Cell Carcinoma of the Lip and Oral Cavity; Stage IVA Squamous Cell Carcinoma of the Lip and Oral Cavity; Stage IVB Squamous Cell Carcinoma of the Lip and Oral Cavity

Casimir energy for two and three superconducting coupled cavities: Numerical calculations

NASA Astrophysics Data System (ADS)

Rosa, L.; Avino, S.; Calloni, E.; Caprara, S.; De Laurentis, M.; De Rosa, R.; Esposito, Giampiero; Grilli, M.; Majorana, E.; Pepe, G. P.; Petrarca, S.; Puppo, P.; Rapagnani, P.; Ricci, F.; Rovelli, C.; Ruggi, P.; Saini, N. L.; Stornaiolo, C.; Tafuri, F.

2017-11-01

In this paper we study the behavior of the Casimir energy of a "multi-cavity" across the transition from the metallic to the superconducting phase of the constituting plates. Our analysis is carried out in the framework of the ARCHIMEDES experiment, aiming at measuring the interaction of the electromagnetic vacuum energy with a gravitational field. For this purpose it is foreseen to modulate the Casimir energy of a layered structure composing a multy-cavity coupled system by inducing a transition from the metallic to the superconducting phase. This implies a thorough study of the behavior of the cavity, in which normal metallic layers are alternated with superconducting layers, across the transition. Our study finds that, because of the coupling between the cavities, mainly mediated by the transverse magnetic modes of the radiation field, the variation of energy across the transition can be very large.

Modified relaxation dynamics and coherent energy exchange in coupled vibration-cavity polaritons

PubMed Central

Dunkelberger, A. D.; Spann, B. T.; Fears, K. P.; Simpkins, B. S.; Owrutsky, J. C.

2016-01-01

Coupling vibrational transitions to resonant optical modes creates vibrational polaritons shifted from the uncoupled molecular resonances and provides a convenient way to modify the energetics of molecular vibrations. This approach is a viable method to explore controlling chemical reactivity. In this work, we report pump–probe infrared spectroscopy of the cavity-coupled C–O stretching band of W(CO)6 and the direct measurement of the lifetime of a vibration-cavity polariton. The upper polariton relaxes 10 times more quickly than the uncoupled vibrational mode. Tuning the polariton energy changes the polariton transient spectra and relaxation times. We also observe quantum beats, so-called vacuum Rabi oscillations, between the upper and lower vibration-cavity polaritons. In addition to establishing that coupling to an optical cavity modifies the energy-transfer dynamics of the coupled molecules, this work points out the possibility of systematic and predictive modification of the excited-state kinetics of vibration-cavity polariton systems. PMID:27874010

Observation of polarization domain wall solitons in weakly birefringent cavity fiber lasers

NASA Astrophysics Data System (ADS)

Zhang, H.; Tang, D. Y.; Zhao, L. M.; Wu, X.

2009-08-01

We report on the experimental observation of two types of phase-locked vector soliton in weakly birefringent cavity erbium-doped fiber lasers. While a phase-locked dark-dark vector soliton was only observed in fiber lasers of positive dispersion, a phase-locked dark-bright vector soliton was obtained in fiber lasers of either positive or negative dispersion. Numerical simulations confirmed the experimental observations and further showed that the observed vector solitons are the two types of phase-locked polarization domain wall solitons theoretically predicted.

Heterodyne optical phase-locking of extended-cavity semiconductor lasers at 9 GHz

NASA Astrophysics Data System (ADS)

Santarelli, G.; Clairon, A.; Lea, S. N.; Tino, G. M.

1994-01-01

In order to stimulate atomic velocity-selective Raman transitions on the 852 nm caesium D 2 line in an atomic fountain clock, two extended-cavity diode lasers have been optically phase-locked at a frequency offset of 9.192 GHz. The measured linewidth (fwhm) of the free-running lasers is 50 kHz. The phase-locked loop bandwidth, evaluated by observing the frequency noise spectrum, is 3.7 MHz and the phase error variance is found to be no more than 4 × 10 -3 rad 2.

Color rendering based on a plasmon fullerene cavity.

PubMed

Tsai, Fu-Cheng; Weng, Cheng-Hsi; Chen, Yu Lim; Shih, Wen-Pin; Chang, Pei-Zen

2018-04-16

Fullerene in the plasmon fullerene cavity is utilized to propagate plasmon energy in order to break the confinement of the plasmonic coupling effect, which relies on the influential near-field optical region. It acts as a plasmonic inductor for coupling gold nano-islands to the gold film; the separation distances of the upper and lower layers are longer than conventional plasmonic cavities. This coupling effect causes the discrete and continuum states to cooperate together in a cavity and produces asymmetric curve lines in the spectra, producing a hybridized resonance. The effect brings about a bright and saturated displaying film with abundant visible colors. In addition, the reflection spectrum is nearly omnidirectional, shifting by only 5% even when the incident angle changes beyond ± 60°. These advantages allow plasmon fullerene cavities to be applied to reflectors, color filters, visible chromatic sensors, and large-area display.

The interaction of ammonia and xenon with the imidazole glycerol phosphate synthase from Thermotoga maritima as detected by NMR spectroscopy

PubMed Central

Liebold, Christoph; List, Felix; Kalbitzer, Hans Robert; Sterner, Reinhard; Brunner, Eike

2010-01-01

The imidazole glycerol phosphate (ImGP) synthase from the hyperthermophilic bacterium Thermotoga maritima is a 1:1 complex of the glutaminase subunit HisH and the cyclase subunit HisF. It has been proposed that ammonia generated by HisH is transported through a channel to the active site of HisF, which generates intermediates of histidine (ImGP) and de novo biosynthesis of 5-aminoimidazole-4-carboxamideribotide. Solution NMR spectroscopy of ammonium chloride-titrated samples was used to study the interaction of NH3 with amino acids inside this channel. Although numerous residues showed 15N chemical shift changes, most of these changes were caused by nonspecific ionic strength effects. However, several interactions appeared to be specific. Remarkably, the amino acid residue Thr 78—which is located in the central channel—shows a large chemical shift change upon titration with ammonium chloride. This result and the reduced catalytic activity of the Thr78Met mutant indicate a special role of this residue in ammonia channeling. To detect and further characterize internal cavities in HisF, which might for example contribute to ammonia channeling, the interaction of HisF with the noble gas xenon was analyzed by solution NMR spectroscopy using 1H-15N HSQC experiments. The results indicate that HisF contains three distinct internal cavities, which could be identified by xenon-induced chemical shift changes of the neighboring amino acid residues. Two of these cavities are located at the active site at opposite ends of the substrate N′-[(5′-phosphoribulosyl)formimino]-5-aminoimidazole-4-carboxamide-ribonucleotide (PRFAR) binding groove. The third cavity is located in the interior of the central β-barrel of HisF and overlaps with the putative ammonia transport channel. PMID:20665694

Concept of multiple-cell cavity for axion dark matter search

NASA Astrophysics Data System (ADS)

Jeong, Junu; Youn, SungWoo; Ahn, Saebyeok; Kim, Jihn E.; Semertzidis, Yannis K.

2018-02-01

In cavity-based axion dark matter search experiments exploring high mass regions, multiple-cavity design is under consideration as a method to increase the detection volume within a given magnet bore. We introduce a new idea, referred to as a multiple-cell cavity, which provides various benefits including a larger detection volume, simpler experimental setup, and easier phase-matching mechanism. We present the characteristics of this concept and demonstrate the experimental feasibility with an example of a double-cell cavity.

Tunability of temperature-dependent absorption in a graphene-based hybrid nanostructure cavity

NASA Astrophysics Data System (ADS)

Rashidi, Arezou; Namdar, Abdolrahman

2018-04-01

Enhanced absorption is obtained in a hybrid nanostructure composed of graphene and one-dimensional photonic crystal as a cavity in the visible wavelength range thanks to the localized electric field around the defect layers. The temperature-induced wavelength shift is revealed in the absorption spectra in which the peak wavelength is red-shifted by increasing the temperature. This temperature dependence comes from the thermal expansion and thermo-optical effects in the constituent layers of the structure. Moreover, the absorption peaks can be adjusted by varying the incident angle. The results show that absorption is sensitive to TE/TM polarization and its peak values for the TE mode are higher than the TM case. Also, the peak wavelength is blue-shifted by increasing the incident angle for both polarizations. Finally, the possibility of tuning the absorption using the electro-optical response of graphene sheets is discussed in detail. We believe our study may be beneficial for designing tunable graphene-based temperature-sensitive absorbers.

Bose–Einstein condensation versus Dicke–Hepp–Lieb transition in an optical cavity

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

Piazza, Francesco, E-mail: francesco.piazza@ph.tum.de; Strack, Philipp; Zwerger, Wilhelm

We provide an exact solution for the interplay between Bose–Einstein condensation and the Dicke–Hepp–Lieb self-organization transition of an ideal Bose gas trapped inside a single-mode optical cavity and subject to a transverse laser drive. Based on an effective action approach, we determine the full phase diagram at arbitrary temperature, which features a bi-critical point where the transitions cross. We calculate the dynamically generated band structure of the atoms and the associated suppression of the critical temperature for Bose–Einstein condensation in the phase with a spontaneous periodic density modulation. Moreover, we determine the evolution of the polariton spectrum due to themore » coupling of the cavity photons and the atomic field near the self-organization transition, which is quite different above or below the Bose–Einstein condensation temperature. At low temperatures, the critical value of the Dicke–Hepp–Lieb transition decreases with temperature and thus thermal fluctuations can enhance the tendency to a periodic arrangement of the atoms. -- Highlights: •Atoms inside a driven cavity can undergo two transitions: self-organization and BEC. •The phase diagram has four phases which coexist at a bi-critical point. •Atom–cavity coupling creates a dynamical lattice for the atoms. •Finite temperature can enhance the tendency towards self-organization. •We calculate the detailed spectrum of the polaritonic excitations.« less

Coherent radio-frequency detection for narrowband direct comb spectroscopy.

PubMed

Anstie, James D; Perrella, Christopher; Light, Philip S; Luiten, Andre N

2016-02-22

We demonstrate a scheme for coherent narrowband direct optical frequency comb spectroscopy. An extended cavity diode laser is injection locked to a single mode of an optical frequency comb, frequency shifted, and used as a local oscillator to optically down-mix the interrogating comb on a fast photodetector. The high spectral coherence of the injection lock generates a microwave frequency comb at the output of the photodiode with very narrow features, enabling spectral information to be further down-mixed to RF frequencies, allowing optical transmittance and phase to be obtained using electronics commonly found in the lab. We demonstrate two methods for achieving this step: a serial mode-by-mode approach and a parallel dual-comb approach, with the Cs D1 transition at 894 nm as a test case.

The fluid property dependency on micro-fluidic characteristics in the deposition process for microfabrication.

PubMed

Chau, S W; Hsu, K L; Chen, S C; Liou, T M; Shih, K C

2004-07-30

The droplet impingement into a cavity at micrometer-scale is one of important fluidic issues for microfabrications, e.g. the inkjet deposition process in the PLED display manufacturing. The related micro-fluidic behaviors in the deposition process should be carefully treated to ensure the desired quality of microfabrication. The droplets generally dispensing from an inkjet head, which contains an array of nozzles, have a volume in several picoliters, while each nozzle responds very quickly and jets the droplets into cavities on substrates with micrometer size. The nature of droplet impingement depends on the fluid properties, the initial state of droplet, the impact parameters and the surface characteristics. The commonly chosen non-dimensional numbers to describe this process are the Weber number, the Reynolds number, the Ohnesorge number, and the Bond number. This paper discusses the influences of fluid properties of a Newtonian fluid, such as surface tension and fluid viscosity, on micro-fluidic characteristics for a certain jetting speed in the deposition process via a numerical approach, which indicates the impingement process consists of four different phases. In the first phase, the droplet stretching outwards rapidly, where inertia force is dominated. In the second phase, the recoiling of droplet is observed, where surface tension becomes the most important force. In the third phase, the gravitational force pulls the droplet surface towards cavity walls. The fourth phase begins when the droplet surface touches cavity walls and ends when the droplet obtains a stable shape. If the fluid viscosity is relatively small, the droplet surface touches cavity walls in the second phase. A stable fluid layer would not form if the viscosity is relatively small.

Lasers with intra-cavity phase elements

NASA Astrophysics Data System (ADS)

Gulses, A. Alkan; Kurtz, Russell; Islas, Gabriel; Anisimov, Igor

2018-02-01

Conventional laser resonators yield multimodal output, especially at high powers and short cavity lengths. Since highorder modes exhibit large divergence, it is desirable to suppress them to improve laser quality. Traditionally, such modal discriminations can be achieved by simple apertures that provide absorptive loss for large diameter modes, while allowing the lower orders, such as the fundamental Gaussian, to pass through. However, modal discrimination may not be sufficient for short-cavity lasers, resulting in multimodal operation as well as power loss and overheating in the absorptive part of the aperture. In research to improve laser mode control with minimal energy loss, systematic experiments have been executed using phase-only elements. These were composed of an intra-cavity step function and a diffractive out-coupler made of a computer-generated hologram. The platform was a 15-cm long solid-state laser that employs a neodymium-doped yttrium orthovanadate crystal rod, producing 1064 nm multimodal laser output. The intra-cavity phase elements (PEs) were shown to be highly effective in obtaining beams with reduced M-squared values and increased output powers, yielding improved values of radiance. The utilization of more sophisticated diffractive elements is promising for more difficult laser systems.

No oral-cavity-only discrimination of purely olfactory odorants.

PubMed

Stephenson, Dejaimenay; Halpern, Bruce P

2009-02-01

The purely olfactory odorants coumarin, octanoic acid, phenylethyl alcohol, and vanillin had been found to be consistently identified when presented retronasally but could not be identified when presented oral-cavity only (OCO). However, OCO discrimination of these odorants was not tested. Consequently, it remained possible that the oral cavity trigeminal system might provide sufficient information to differentiate these purely olfactory odorants. To evaluate this, 20 participants attempted to discriminate vapor-phase coumarin, octanoic acid, phenylethyl alcohol, and vanillin and, as a control, the trigeminal stimulus peppermint extract, from their glycerin solvent, all presented OCO. None of the purely olfactory odorants could be discriminated OCO, but, as expected, peppermint extract was consistently discriminated. This inability to discriminate clarifies and expands the previous report of lack of OCO identification of purely olfactory odorants. Taken together with prior data, these results suggest that the oral cavity trigeminal system is fully unresponsive to these odorants in vapor phase and that coumarin, octanoic acid, phenylethyl alcohol, and vanillin are indeed purely olfactory stimuli. The OCO discrimination of peppermint extract demonstrated that the absence of discrimination for the purely olfactory odorants was odorant dependent and confirmed that the oral cavity trigeminal system will provide differential response information to some vapor-phase stimuli.

Exploring cavity-mediated long-range interactions in a dilute quantum gas

NASA Astrophysics Data System (ADS)

Landig, Renate; Mottl, Rafael; Brennecke, Ferdinand; Baumann, Kristian; Donner, Tobias; Esslinger, Tilman

2013-05-01

We report on the observation of a characteristic change in the excitation spectrum of a Bose-Einstein condensate and increased density fluctuations due to cavity-mediated atom-atom interactions. Increasing the strength of the interaction leads to a softening of an excitation mode at finite momentum, preceding a superfluid to supersolid phase transition. The observed behavior is reminiscent of a roton minimum, as predicted for quantum gases with long-range interactions. We create long-range interactions in the BEC using a non-resonant transverse pump beam which induces virtual photon exchange via the vacuum field of an optical cavity. The mode softening is spectroscopically studied across the phase transition using a variant of Bragg spectroscopy. At the phase transition a diverging density response is observed which is linked to increased density fluctuations. Using the cavity dissipation channel we monitor these fluctuations in real-time and identify the influence of measurement backaction onto the critical behavior of the system.

Optical heterodyne detection for cavity ring-down spectroscopy

DOEpatents

Levenson, Marc D.; Paldus, Barbara A.; Zare, Richard N.

2000-07-25

A cavity ring-down system for performing cavity ring-down spectroscopy (CRDS) using optical heterodyne detection of a ring-down wave E.sub.RD during a ring-down phase or a ring-up wave E.sub.RU during a ring up phase. The system sends a local oscillator wave E.sub.LO and a signal wave E.sub.SIGNAL to the cavity, preferably a ring resonator, and derives an interference signal from the combined local oscillator wave E.sub.LO and the ring-down wave E.sub.RD (or ring-up wave E.sub.RU). The local oscillator wave E.sub.LO has a first polarization and the ring-down wave E.sub.RD has a second polarization different from the first polarization. The system has a combining arrangement for combining or overlapping local oscillator wave E.sub.LO and the ring-down wave E.sub.RD at a photodetector, which receives the interference signal and generates a heterodyne current I.sub.H therefrom. Frequency and phase differences between the waves are adjustable.

Progress on Raman laser for sodium resonance fluorescence lidar

NASA Astrophysics Data System (ADS)

Li, Steven X.; Yu, Anthony W.; Krainak, Michael A.; Bai, Yingxin; Konoplev, Oleg; Fahey, Molly E.; Numata, Kenji

2018-02-01

We are developing a Q-switched narrow linewidth intra-cavity Raman laser for a space based sodium lidar application. A novel Raman laser injection seeding scheme is proposed and is experimentally verified. A Q-switched, diode pumped, c-cut Nd:YVO4 laser has been designed to emit a fundamental wavelength at 1066.6 nm. This fundamental wavelength is used as the pump in an intra-cavity Raman conversion in a Gd0.2Y0.8VO4 composite material. By tuning the temperature of the crystal, we tuned the Raman shifting to the desired sodium absorption line. A diode end pumped, T-shaped laser cavity has been built for experimental investigation. The fundamental pump laser cavity is a twisted mode cavity to eliminate the spatial hole burning for effective injection seeding. The Raman laser cavity is a linear standing wave cavity because Raman gain medium does not suffer spatial hole burning as traditional laser gain medium. The linewidth and temporal profile of the Raman laser is experimentally investigated with narrow and broadband fundamental pump emission. We have, for the first time, demonstrated an injection seeded, high peak power, narrow linewidth intra-cavity Raman laser for potential use in a sodium resonance fluorescence lidar.

Superconducting resonator used as a beam phase detector.

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

Sharamentov, S. I.; Pardo, R. C.; Ostroumov, P. N.

2003-05-01

Beam-bunch arrival time has been measured for the first time by operating superconducting cavities, normally part of the linac accelerator array, in a bunch-detecting mode. The very high Q of the superconducting cavities provides high sensitivity and allows for phase-detecting low-current beams. In detecting mode, the resonator is operated at a very low field level comparable to the field induced by the bunched beam. Because of this, the rf field in the cavity is a superposition of a 'pure' (or reference) rf and the beam-induced signal. A new method of circular phase rotation (CPR), allowing extraction of the beam phasemore » information from the composite rf field was developed. Arrival time phase determination with CPR is better than 1{sup o} (at 48 MHz) for a beam current of 100 nA. The electronics design is described and experimental data are presented.« less

Electrically injected visible vertical cavity surface emitting laser diodes

DOEpatents

Schneider, Richard P.; Lott, James A.

1994-01-01

Visible laser light output from an electrically injected vertical cavity surface emitting laser (VSCEL) diode is enabled by the addition of phase-matching spacer layers on either side of the active region to form the optical cavity. The spacer layers comprise InAlP which act as charge carrier confinement means. Distributed Bragg reflector layers are formed on either side of the optical cavity to act as mirrors.

Electrically injected visible vertical cavity surface emitting laser diodes

DOEpatents

Schneider, R.P.; Lott, J.A.

1994-09-27

Visible laser light output from an electrically injected vertical cavity surface emitting laser (VSCEL) diode is enabled by the addition of phase-matching spacer layers on either side of the active region to form the optical cavity. The spacer layers comprise InAlP which act as charge carrier confinement means. Distributed Bragg reflector layers are formed on either side of the optical cavity to act as mirrors. 5 figs.

Multistability of cavity exciton polaritons affected by the thermally generated exciton reservoir

NASA Astrophysics Data System (ADS)

Vishnevsky, D. V.; Solnyshkov, D. D.; Gippius, N. A.; Malpuech, G.

2012-04-01

Recently the buildup of an excitonic reservoir in a GaAs cavity polariton system under quasiresonant pumping has been demonstrated experimentally [S. S. Gavrilov , JETP Lett.JTPLA20021-364010.1134/S0021364010150105 92, 171 (2010)]. We show that in microcavities having a small Rabi splitting (typically GaAs cavities with a single quantum well), this reservoir can be efficiently populated by polariton-phonon scattering. We consider the influence of the exciton reservoir on the energy shifts of the resonantly pumped polariton modes. We show that the presence of this reservoir effectively reduces the spin anisotropy of the polariton-polariton interaction, in agreement with recent experimental measurements, where the multistability of cavity polaritons has been analyzed [T. K. Paraiso , Nat. Mater.1476-112210.1038/nmat2787 9, 655 (2010)].

High speed strain measurement of active mode locking FBG laser sensor using chirped FBG cavity

NASA Astrophysics Data System (ADS)

Kim, Gyeong Hun; Kim, Joon Young; Park, Chang Hyun; Kim, Chang-Seok; Lee, Hwi Don; Chung, Youngjoo

2017-04-01

We propose a high speed strain measurement method using an active mode locking (AML) fiber Bragg grating (FBG) laser sensor with a chirped FBG cavity. The mode-locked frequency of the AML laser depends on both the position and Bragg wavelength of the FBG. Thus, the mode-locked frequency of cascaded FBGs can be detected independently along the cavity length of cascaded FBGs. The strain across FBGs can be interrogated dynamically by monitoring the change in mode-locked frequency. In this respect, the chirped FBG critically improves the frequency sensitivity to Bragg wavelength shift as a function of increasing dispersion in the AML cavity. The strain measurement of the FBG sensor shows a highly linear response, with an R-squared value of 0.9997.

High Power RF Testing of A 3-Cell Superconducting Traveling Wave Accelerating Structure

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

Kanareykin, Alex; Kostin, Romna; Avrakhov, Pavel

Euclid Techlabs has completed the Phase II SBIR project, entitled “High Power RF Testing of a 3-Cell Superconducting Traveling Wave Accelerating Structure” under Grant #DE-SC0006300. In this final technical report, we summarize the major achievements of Phase I of the project and review the details of Phase II of the project. The accelerating gradient in a superconducting structure is limited mainly by quenching, i.e., by the maximum surface RF magnetic field. Various techniques have been developed to increase the gradient. A traveling wave accelerating SC structure with a feedback waveguide was suggested to allow an increased transit time factor andmore » ultimately, a maximum gradient that is 22%-24% higher than in the best of the time standing wave SRF cavity solution. The proposed structure has an additional benefit in that it can be fabricated much longer than the standing wave ones that are limited by the field flatness factor. Taken together, all of these factors will result in a significant overall length and, correspondingly cost reduction of the SRF based linear collider ILC or SRF technology based FELs. In Phase I of this project, a 3-cell L-band SC traveling wave cavity was designed. Cavity shape, surface field ratios, inter-cell coupling coefficients, accelerating field flatness have been reviewed with the analysis of tuning issues. Moreover, the technological aspects of SC traveling wave accelerating structure fabrication have been studied. As the next step in the project, the Phase II experimental program included engineering design, manufacturing, surface processing and high gradient testing. Euclid Techlabs, LLC contracted AES, Inc. to manufacture two niobium cavities. Euclid Techlabs cold tested traveling wave regime in the cavity, and the results showed very good agreement with mathematical model specially developed for superconducting traveling wave cavity performance analysis. Traveling wave regime was adjusted by amplitude and phase variation of input signals due to application of developed power feeding scheme. Traveling wave excitation, adjustment and detection were successfully tested. Auxiliary equipment required for high power test such as the tuner, power and measure couplers, holding plates for VTS at Fermilab were developed and successfully tested. Both TW SRF cavities were fabricated by AES, Inc. without stiffening ribs before this company closed their production facility. Currently Roark EB welding company is finishing now welding process of the cavity for the high power testing at Fermilab VTS. Successful demonstration of high gradients in the 3-cell cavity along with studies of traveling wave excitation and tuning issues is leading to successful development of superconducting traveling wave technology for ILC applications and other future high energy SC accelerators.« less

[Palatograms and linguograms for studying misarticulation following surgery for tumors of the tongue and oral cavity floor].

PubMed

Lewandowski, Leszek

2006-01-01

This work deals with the mechanism of misarticulation following surgery for malignancies in the oral cavity. The underlying cause was dysfunction of the tongue due to partial or total resection, consequences of the resection of the mandible together with the oral cavity floor, or dysfunkction of the lower lip failing to seal the space of Donders. Anatomic alternations reveal themselves as shifts in the points of contact between structures of the articulation system noticeable on palatograms or linguograms. Limited mobility of tongue tip may affect speech, particularly in the case of sounds of the first and second articulation zone.

Phase-sensitive reflection technique for characterization of a fabry-perot interferometer.

PubMed

Slagmolen, B J; Gray, M B; Baigent, K G; McClelland, D E

2000-07-20

Using a radio frequency coherent modulation and demodulation technique, we explicitly measure both the amplitude and the phase response of Fabry-Perot interferometers in reflection. This allows us to differentiate clearly between overcoupled and undercoupled cavities and allows a detailed measurement of the full width at half-maximum, the free spectral range, and the finesse of the cavities.

Quantum noise in a transversely-pumped-cavity Bose-Hubbard model

NASA Astrophysics Data System (ADS)

Nagy, Dávid; Kónya, Gábor; Domokos, Peter; Szirmai, Gergely

2018-06-01

We investigate the quantum measurement noise effects on the dynamics of an atomic Bose lattice gas inside an optical resonator. We describe the dynamics by means of a hybrid model consisting of a Bose-Hubbard Hamiltonian for the atoms and a Heisenberg-Langevin equation for the lossy cavity-field mode. We assume that the atoms are prepared initially in the ground state of the lattice Hamiltonian and then start to interact with the cavity mode. We show that the cavity-field fluctuations originating from the dissipative outcoupling of photons from the resonator lead to vastly different effects in the different possible ground-state phases, i.e., the superfluid, the supersolid, the Mott and charge-density-wave phases. In the former two phases with the presence of a superfluid wavefunction, the quantum measurement noise appears as a driving term leading to depletion of the ground state. The timescale for the system to leave the ground state is presented in a simple analytical form. For the latter two incompressible phases, the quantum noise results in the fluctuation of the chemical potential. We derive an analytical expression for the corresponding broadening of the quasiparticle resonances.

A Digital Phase Lock Loop for an External Cavity Diode Laser

NASA Astrophysics Data System (ADS)

Wang, Xiao-Long; Tao, Tian-Jiong; Cheng, Bing; Wu, Bin; Xu, Yun-Fei; Wang, Zhao-Ying; Lin, Qiang

2011-08-01

A digital optical phase lock loop (OPLL) is implemented to synchronize the frequency and phase between two external cavity diode lasers (ECDL), generating Raman pulses for atom interferometry. The setup involves all-digital phase detection and a programmable digital proportional-integral-derivative (PID) loop in locking. The lock generates a narrow beat-note linewidth below 1 Hz and low phase-noise of 0.03rad2 between the master and slave ECDLs. The lock proves to be stable and robust, and all the locking parameters can be set and optimized on a computer interface with convenience, making the lock adaptable to various setups of laser systems.

Quantitative phase imaging using four interferograms with special phase shifts by dual-wavelength in-line phase-shifting interferometry

NASA Astrophysics Data System (ADS)

Xu, Xiaoqing; Wang, Yawei; Ji, Ying; Xu, Yuanyuan; Xie, Ming; Han, Hao

2018-05-01

A new approach of quantitative phase imaging using four interferograms with special phase shifts in dual-wavelength in-line phase-shifting interferometry is presented. In this method, positive negative 2π phase shifts are employed to easily separate the incoherent addition of two single-wavelength interferograms by combining the phase-shifting technique with the subtraction procedure, then the quantitative phase at one of both wavelengths can be achieved based on two intensities without the corresponding dc terms by the use of the character of the trigonometric function. The quantitative phase of the other wavelength can be retrieved from two dc-term suppressed intensities obtained by employing the two-step phase-shifting technique or the filtering technique in the frequency domain. The proposed method is illustrated with theory, and its effectiveness is demonstrated by simulation experiments of the spherical cap and the HeLa cell, respectively.

Texas ratsnake predation on southern flying squirrels in red-cockaded woodpecker cavities

Treesearch

D. Craig Rudolph; Richard R. Schaefer; Josh B. Pierce; Dan Saenz; Richard N. Conner

2009-01-01

Elaphe spp. (ratsnakes) are frequent predators on cavity-nesting birds and other vertebrates, including Glaucomys volans (Southern Flying Squirrels). They are known predators of Picoides borealis (Red-cockaded Woodpeckers), especially during the nestling phase. Picoides borealis cavities are frequently occupied by Southern Flying Squirrels, often several squirrels per...

Cavity electromagnetically induced transparency with Rydberg atoms

NASA Astrophysics Data System (ADS)

Bakar Ali, Abu; Ziauddin

2018-02-01

Cavity electromagnetically induced transparency (EIT) is revisited via the input probe field intensity. A strongly interacting Rydberg atomic medium ensemble is considered in a cavity, where atoms behave as superatoms (SAs) under the dipole blockade mechanism. Each atom in the strongly interacting Rydberg atomic medium (87 Rb) follows a three-level cascade atomic configuration. A strong control and weak probe field are employed in the cavity with the ensemble of Rydberg atoms. The features of the reflected and transmitted probe light are studied under the influence of the input probe field intensity. A transparency peak (cavity EIT) is revealed at a resonance condition for small values of input probe field intensity. The manipulation of the cavity EIT is reported by tuning the strength of the input probe field intensity. Further, the phase and group delay of the transmitted and reflected probe light are studied. It is found that group delay and phase in the reflected light are negative, while for the transmitted light they are positive. The magnitude control of group delay in the transmitted and reflected light is investigated via the input probe field intensity.

Resonator modes and mode dynamics for an external cavity-coupled laser array

NASA Astrophysics Data System (ADS)

Nair, Niketh; Bochove, Erik J.; Aceves, Alejandro B.; Zunoubi, Mohammad R.; Braiman, Yehuda

2015-03-01

Employing a Fox-Li approach, we derived the cold-cavity mode structure and a coupled mode theory for a phased array of N single-transverse-mode active waveguides with feedback from an external cavity. We applied the analysis to a system with arbitrary laser lengths, external cavity design and coupling strengths to the external cavity. The entire system was treated as a single resonator. The effect of the external cavity was modeled by a set of boundary conditions expressed by an N-by-N frequency-dependent matrix relation between incident and reflected fields at the interface with the external cavity. The coupled mode theory can be adapted to various types of gain media and internal and external cavity designs.

High-speed optical phase-shifting apparatus

DOEpatents

Zortman, William A.

2016-11-08

An optical phase shifter includes an optical waveguide, a plurality of partial phase shifting elements arranged sequentially, and control circuitry electrically coupled to the partial phase shifting elements. The control circuitry is adapted to provide an activating signal to each of the N partial phase shifting elements such that the signal is delayed by a clock cycle between adjacent partial phase shifting elements in the sequence. The transit time for a guided optical pulse train between the input edges of consecutive partial phase shifting elements in the sequence is arranged to be equal to a clock cycle, thereby enabling pipelined processing of the optical pulses.

Beam shuttering interferometer and method

DOEpatents

Deason, V.A.; Lassahn, G.D.

1993-07-27

A method and apparatus resulting in the simplification of phase shifting interferometry by eliminating the requirement to know the phase shift between interferograms or to keep the phase shift between interferograms constant. The present invention provides a simple, inexpensive means to shutter each independent beam of the interferometer in order to facilitate the data acquisition requirements for optical interferometry and phase shifting interferometry. By eliminating the requirement to know the phase shift between interferograms or to keep the phase shift constant, a simple, economical means and apparatus for performing the technique of phase shifting interferometry is provide which, by thermally expanding a fiber optical cable changes the optical path distance of one incident beam relative to another.

Beam shuttering interferometer and method

DOEpatents

Deason, Vance A.; Lassahn, Gordon D.

1993-01-01

A method and apparatus resulting in the simplification of phase shifting interferometry by eliminating the requirement to know the phase shift between interferograms or to keep the phase shift between interferograms constant. The present invention provides a simple, inexpensive means to shutter each independent beam of the interferometer in order to facilitate the data acquisition requirements for optical interferometry and phase shifting interferometry. By eliminating the requirement to know the phase shift between interferograms or to keep the phase shift constant, a simple, economical means and apparatus for performing the technique of phase shifting interferometry is provide which, by thermally expanding a fiber optical cable changes the optical path distance of one incident beam relative to another.

Phase control of entanglement and quantum steering in a three-mode optomechanical system

NASA Astrophysics Data System (ADS)

Sun, F. X.; Mao, D.; Dai, Y. T.; Ficek, Z.; He, Q. Y.; Gong, Q. H.

2017-12-01

The theory of phase control of coherence, entanglement and quantum steering is developed for an optomechanical system composed of a single mode cavity containing a partially transmitting dielectric membrane and driven by short laser pulses. The membrane divides the cavity into two mutually coupled optomechanical cavities resulting in an effective three-mode closed loop system, two field modes of the two cavities and a mechanical mode representing the oscillating membrane. The closed loop in the coupling creates interfering channels which depend on the relative phase of the coupling strengths of the field modes to the mechanical mode. Populations and correlations of the output modes are calculated analytically and show several interesting phase dependent effects such as reversible population transfer from one field mode to the other, creation of collective modes, and induced coherence without induced emission. We find that these effects result from perfect mutual coherence between the field modes which is preserved even if one of the modes is not populated. The inseparability criterion for the output modes is also investigated and we find that entanglement may occur only between the field modes and the mechanical mode. We show that depending on the phase, the field modes can act on the mechanical mode collectively or individually resulting, respectively, in tripartite or bipartite entanglement. In addition, we examine the phase sensitivity of quantum steering of the mechanical mode by the field modes. Deterministic phase transfer of the steering from bipartite to collective is predicted and optimum steering corresponding to perfect EPR state can be achieved. These different types of quantum steering can be distinguished experimentally by measuring the coincidence rate between two detectors adjusted to collect photons of the output cavity modes. In particular, we find that the minima of the interference pattern of the coincidence rate signal the bipartite steering, while the maxima signal the collective steering.

Mode-locking of a terahertz laser by direct phase synchronization.

PubMed

Maysonnave, J; Maussang, K; Freeman, J R; Jukam, N; Madéo, J; Cavalié, P; Rungsawang, R; Khanna, S P; Linfield, E H; Davies, A G; Beere, H E; Ritchie, D A; Dhillon, S S; Tignon, J

2012-09-10

A novel scheme to achieve mode-locking of a multimode laser is demonstrated. Traditional methods to produce ultrashort laser pulses are based on modulating the cavity gain or losses at the cavity roundtrip frequency, favoring the pulsed emission. Here, we rather directly act on the phases of the modes, resulting in constructive interference for the appropriated phase relationship. This was performed on a terahertz quantum cascade laser by multimode injection seeding with an external terahertz pulse, resulting in phase mode-locked terahertz laser pulses of 9 ps duration, characterized unambiguously in the time domain.

Coupled-cavity drift-tube linac

DOEpatents

Billen, James H.

1996-01-01

A coupled-cavity drift-tube linac (CCDTL) combines features of the Alvarez drift-tube linac (DTL) and the .pi.-mode coupled-cavity linac (CCL). In one embodiment, each accelerating cavity is a two-cell, 0-mode DTL. The center-to-center distance between accelerating gaps is .beta..lambda., where .lambda. is the free-space wavelength of the resonant mode. Adjacent accelerating cavities have oppositely directed electric fields, alternating in phase by 180 degrees. The chain of cavities operates in a .pi./2 structure mode so the coupling cavities are nominally unexcited. The CCDTL configuration provides an rf structure with high shunt impedance for intermediate velocity charged particles, i.e., particles with energies in the 20-200 MeV range.

Coupled-cavity drift-tube linac

DOEpatents

Billen, J.H.

1996-11-26

A coupled-cavity drift-tube linac (CCDTL) combines features of the Alvarez drift-tube linac (DTL) and the {pi}-mode coupled-cavity linac (CCL). In one embodiment, each accelerating cavity is a two-cell, 0-mode DTL. The center-to-center distance between accelerating gaps is {beta}{lambda}, where {lambda} is the free-space wavelength of the resonant mode. Adjacent accelerating cavities have oppositely directed electric fields, alternating in phase by 180 degrees. The chain of cavities operates in a {pi}/2 structure mode so the coupling cavities are nominally unexcited. The CCDTL configuration provides an rf structure with high shunt impedance for intermediate velocity charged particles, i.e., particles with energies in the 20-200 MeV range. 5 figs.

Progress towards 3-cell superconducting traveling wave cavity cryogenic test

NASA Astrophysics Data System (ADS)

Kostin, R.; Avrakhov, P.; Kanareykin, A.; Yakovlev, V.; Solyak, N.

2017-12-01

This paper describes a superconducting L-band travelling wave cavity for electron linacs as an alternative to the 9-cell superconducting standing wave Tesla type cavity. A superconducting travelling wave cavity may provide 20-40% higher accelerating gradient by comparison with conventional cavities. This feature arises from an opportunity to use a smaller phase advance per cell which increases the transit time factor and affords the opportunity to use longer cavities because of its significantly smaller sensitivity to manufacturing errors. Two prototype superconducting travelling wave cavities were designed and manufactured for a high gradient travelling wave demonstration at cryogenic temperature. This paper presents the main milestones achieved towards this test.

Measurements of Nascent Soot Using a Cavity Attenauted Phase Shift (CAPS)-based Single Scattering Albedo Monitor

NASA Astrophysics Data System (ADS)

Freedman, A.; Onasch, T. B.; Renbaum-Wollf, L.; Lambe, A. T.; Davidovits, P.; Kebabian, P. L.

2015-12-01

Accurate, as compared to precise, measurement of aerosol absorption has always posed a significant problem for the particle radiative properties community. Filter-based instruments do not actually measure absorption but rather light transmission through the filter; absorption must be derived from this data using multiple corrections. The potential for matrix-induced effects is also great for organic-laden aerosols. The introduction of true in situ measurement instruments using photoacoustic or photothermal interferometric techniques represents a significant advance in the state-of-the-art. However, measurement artifacts caused by changes in humidity still represent a significant hurdle as does the lack of a good calibration standard at most measurement wavelengths. And, in the absence of any particle-based absorption standard, there is no way to demonstrate any real level of accuracy. We, along with others, have proposed that under the circumstance of low single scattering albedo (SSA), absorption is best determined by difference using measurement of total extinction and scattering. We discuss a robust, compact, field deployable instrument (the CAPS PMssa) that simultaneously measures airborne particle light extinction and scattering coefficients and thus the single scattering albedo (SSA) on the same sample volume. The extinction measurement is based on cavity attenuated phase shift (CAPS) techniques as employed in the CAPS PMex particle extinction monitor; scattering is measured using integrating nephelometry by incorporating a Lambertian integrating sphere within the sample cell. The scattering measurement is calibrated using the extinction measurement of non-absorbing particles. For small particles and low SSA, absorption can be measured with an accuracy of 6-8% at absorption levels as low as a few Mm-1. We present new results of the measurement of the mass absorption coefficient (MAC) of soot generated by an inverted methane diffusion flame at 630 nm. A value of 6.60 ±0.2 m2 g-1 was determined where the uncertainty refers to the precision of the measurement. The overall accuracy of the measurement, traceable to the properties of polystyrene latex particles, is estimated to be better than ±10%.

A novel nano-sensor based on optomechanical crystal cavity

NASA Astrophysics Data System (ADS)

Zhang, Yeping; Ai, Jie; Ma, Jingfang

2017-10-01

Optical devices based on new sensing principle are widely used in biochemical and medical area. Nowadays, mass sensing based on monitoring the frequency shifts induced by added mass in oscillators is a well-known and widely used technique. It is interesting to note that for nanoscience and nanotechnology applications there is a strong demand for very sensitive mass sensors, being the target a sensor for single molecule detection. The desired mass resolution for very few or even single molecule detection, has to be below the femtogram range. Considering the strong interaction between high co-localized optical mode and mechanical mode in optomechanical crystal (OMC) cavities, we investigate OMC splitnanobeam cavities in silicon operating near at the 1550nm to achieve high optomechanical coupling rate and ultra-small motion mass. Theoretical investigations of the optical and mechanical characteristic for the proposed cavity are carried out. By adjusting the structural parameters, the cavity's effective motion mass below 10fg and mechanical frequency exceed 10GHz. The transmission spectrum of the cavity is sensitive to the sample which located on the center of the cavity. We conducted the fabrication and the characterization of this cavity sensor on the silicon-on-insulator (SOI) chip. By using vertical coupling between the tapered fiber and the SOI chip, we measured the transmission spectrum of the cavity, and verify this cavity is promising for ultimate precision mass sensing and detection.

Passive cavity surface-emitting lasers: option of temperature-insensitive lasing wavelength for uncooled dense wavelength division multiplexing systems

NASA Astrophysics Data System (ADS)

Shchukin, V. A.; Ledentsov, N. N.; Slight, T.; Meredith, W.; Gordeev, N. Y.; Nadtochy, A. M.; Payusov, A. S.; Maximov, M. V.; Blokhin, S. A.; Blokhin, A. A.; Zadiranov, Yu. M.; Maleev, N. A.; Ustinov, V. M.; Choquette, K. D.

2016-03-01

A concept of passive cavity surface-emitting laser is proposed aimed to control the temperature shift of the lasing wavelength. The device contains an all-semiconductor bottom distributed Bragg reflector (DBR), in which the active medium is placed, a dielectric resonant cavity and a dielectric top DBR, wherein at least one of the dielectric materials has a negative temperature coefficient of the refractive index, dn/dT < 0. This is shown to be the case for commonly used dielectric systems SiO2/TiO2 and SiO2/Ta2O5. Two SiO2/TiO2 resonant structures having a cavity either of SiO2 or TiO2 were deposited on a substrate, their optical power reflectance spectra were measured at various temperatures, and refractive index temperature coefficients were extracted, dn/dT = 0.0021 K-1 for SiO2 and dn/dT = -0.0092 K-1 for TiO2. Using such dielectric materials allows designing passive cavity surface-emitting lasers having on purpose either positive, or zero, or negative temperature shift of the lasing wavelength dλ/dT. A design for temperature-insensitive lasing wavelength (dλ/dT = 0) is proposed. Employing devices with temperature-insensitive lasing wavelength in wavelength division multiplexing systems may allow significant reducing of the spectral separation between transmission channels and an increase in number of channels for a defined spectral interval enabling low cost energy efficient uncooled devices.

Study of nanometer-level precise phase-shift system used in electronic speckle shearography and phase-shift pattern interferometry

NASA Astrophysics Data System (ADS)

Jing, Chao; Liu, Zhongling; Zhou, Ge; Zhang, Yimo

2011-11-01

The nanometer-level precise phase-shift system is designed to realize the phase-shift interferometry in electronic speckle shearography pattern interferometry. The PZT is used as driving component of phase-shift system and translation component of flexure hinge is developed to realize micro displacement of non-friction and non-clearance. Closed-loop control system is designed for high-precision micro displacement, in which embedded digital control system is developed for completing control algorithm and capacitive sensor is used as feedback part for measuring micro displacement in real time. Dynamic model and control model of the nanometer-level precise phase-shift system is analyzed, and high-precision micro displacement is realized with digital PID control algorithm on this basis. It is proved with experiments that the location precision of the precise phase-shift system to step signal of displacement is less than 2nm and the location precision to continuous signal of displacement is less than 5nm, which is satisfied with the request of the electronic speckle shearography and phase-shift pattern interferometry. The stripe images of four-step phase-shift interferometry and the final phase distributed image correlated with distortion of objects are listed in this paper to prove the validity of nanometer-level precise phase-shift system.

Quantum and classical chaos in kicked coupled Jaynes-Cummings cavities

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

Hayward, A. L. C.; Greentree, Andrew D.

2010-06-15

We consider two Jaynes-Cummings cavities coupled periodically with a photon hopping term. The semiclassical phase space is chaotic, with regions of stability over some ranges of the parameters. The quantum case exhibits dynamic localization and dynamic tunneling between classically forbidden regions. We explore the correspondence between the classical and quantum phase space and propose an implementation in a circuit QED system.

Temporal dynamics of circadian phase shifting response to consecutive night shifts in healthcare workers: role of light-dark exposure.

PubMed

Stone, Julia E; Sletten, Tracey L; Magee, Michelle; Ganesan, Saranea; Mulhall, Megan D; Collins, Allison; Howard, Mark; Lockley, Steven W; Rajaratnam, Shantha M W

2018-06-01

Shift work is highly prevalent and is associated with significant adverse health impacts. There is substantial inter-individual variability in the way the circadian clock responds to changing shift cycles. The mechanisms underlying this variability are not well understood. We tested the hypothesis that light-dark exposure is a significant contributor to this variability; when combined with diurnal preference, the relative timing of light exposure accounted for 71% of individual variability in circadian phase response to night shift work. These results will drive development of personalised approaches to manage circadian disruption among shift workers and other vulnerable populations to potentially reduce the increased risk of disease in these populations. Night shift workers show highly variable rates of circadian adaptation. This study examined the relationship between light exposure patterns and the magnitude of circadian phase resetting in response to night shift work. In 21 participants (nursing and medical staff in an intensive care unit) circadian phase was measured using 6-sulphatoxymelatonin at baseline (day/evening shifts or days off) and after 3-4 consecutive night shifts. Daily light exposure was examined relative to individual circadian phase to quantify light intensity in the phase delay and phase advance portions of the light phase response curve (PRC). There was substantial inter-individual variability in the direction and magnitude of phase shift after three or four consecutive night shifts (mean phase delay -1:08 ± 1:31 h; range -3:43 h delay to +3:07 h phase advance). The relative difference in the distribution of light relative to the PRC combined with diurnal preference accounted for 71% of the variability in phase shift. Regression analysis incorporating these factors estimated phase shift to within ±60 min in 85% of participants. No participants met criteria for partial adaptation to night work after three or four consecutive night shifts. Our findings provide evidence that the phase resetting that does occur is based on individual light exposure patterns relative to an individual's baseline circadian phase. Thus, a 'one size fits all' approach to promoting adaptation to shift work using light therapy, implemented without knowledge of circadian phase, may not be efficacious for all individuals. © 2018 Monash University. The Journal of Physiology © 2018 The Physiological Society.

Tunable high-order-sideband generation and carrier-envelope-phase-dependent effects via microwave fields in hybrid electro-optomechanical systems

NASA Astrophysics Data System (ADS)

Si, Liu-Gang; Guo, Ling-Xia; Xiong, Hao; Wu, Ying

2018-02-01

We investigate the high-order-sideband generation (HSG) in a hybrid cavity electro-photomechanical system in which an optical cavity is driven by two optical fields (a monochromatic pump field and a nanosecond Gaussian probe pulse with huge numbers of wave cycles), and at the same time a microwave cavity is driven by a monochromatic ac voltage bias. We show that even if the input powers of two driven optical fields are comparatively low the HSG spectra can be induced and enhanced, and the sideband plateau is extended remarkably with the power of the ac voltage bias increasing. It is also shown that the driven ac voltage bias has profound effects on the carrier-envelope-phase-dependent effects of the HSG in the hybrid cavity electro-photomechanical system. Our research may provide an effective way to control the HSG of optical fields by using microwave fields in cavity optomechanics systems.

Results from phase 1 of the HAYSTAC microwave cavity axion experiment

NASA Astrophysics Data System (ADS)

Zhong, L.; Al Kenany, S.; Backes, K. M.; Brubaker, B. M.; Cahn, S. B.; Carosi, G.; Gurevich, Y. V.; Kindel, W. F.; Lamoreaux, S. K.; Lehnert, K. W.; Lewis, S. M.; Malnou, M.; Maruyama, R. H.; Palken, D. A.; Rapidis, N. M.; Root, J. R.; Simanovskaia, M.; Shokair, T. M.; Speller, D. H.; Urdinaran, I.; van Bibber, K. A.

2018-05-01

We report on the results from a search for dark matter axions with the HAYSTAC experiment using a microwave cavity detector at frequencies between 5.6 and 5.8 GHz. We exclude axion models with two photon coupling ga γ γ≳2 ×10-14 GeV-1 , a factor of 2.7 above the benchmark KSVZ model over the mass range 23.15

CAVITY EXCITATION CIRCUIT

DOEpatents

Franck, J.V.

1959-10-20

An electronic oscillator is described for energizing a resonant cavity and to a system for stabilizing the operatin g frequency of the oscillator at the particular frequency necessary to establish a particular preferred field configuration or mode in the cavity, in this instance a linear accelerator. A freely rnnning oscillator has an output coupled to a resonant cavity wherein a field may be built up at any one of several adjacent frequencies. A pickup loop in the cavity is suitably shielded and positioned in the cavity so that only energy at the panticular desired frequency is fed back to stabilize the oscillator. A phase and gain control is in cluded in the feedback line.

Transmission electron microscopy characterization of macromolecular domain cavities and microstructure of single-crystal calcite tooth plates of the sea urchin Lytechinus variegatus.

PubMed

Robach, J S; Stock, S R; Veis, A

2005-07-01

The calcite plates and prisms in Lytechinus variegatus teeth form a complex biocomposite and employ a myriad of strengthening and toughening strategies. These crystal elements have macromolecule-containing internal cavities that may act to prevent cleavage. Transmission electron microscopy employing a small objective aperture was used to quantify several characteristics of these cavities. Cavity diameters ranged from 10 to 225 nm, the mean cavity diameter was between 50 and 60 nm, and cavities comprised approximately 20% of the volume of the crystal. Some cavities exhibited faceting and trace analysis identified these planes as being predominately of {1014} type. Through focus series of micrographs show the cavities were homogeneously distributed throughout the foil. The electron beam decomposed a substance within cavities and this suggests that these cavities are filled with a hydrated organic phase.

In-line phase shift tomosynthesis

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

Hammonds, Jeffrey C.; Price, Ronald R.; Pickens, David R.

2013-08-15

Purpose: The purpose of this work is to (1) demonstrate laboratory measurements of phase shift images derived from in-line phase-contrast radiographs using the attenuation-partition based algorithm (APBA) of Yan et al.[Opt. Express 18(15), 16074–16089 (2010)], (2) verify that the APBA reconstructed images obey the linearity principle, and (3) reconstruct tomosynthesis phase shift images from a collection of angularly sampled planar phase shift images.Methods: An unmodified, commercially available cabinet x-ray system (Faxitron LX-60) was used in this experiment. This system contains a tungsten anode x-ray tube with a nominal focal spot size of 10 μm. The digital detector uses CsI/CMOS withmore » a pixel size of 50 × 50 μm. The phantoms used consisted of one acrylic plate, two polystyrene plates, and a habanero pepper. Tomosynthesis images were reconstructed from 51 images acquired over a ±25° arc. All phase shift images were reconstructed using the APBA.Results: Image contrast derived from the planar phase shift image of an acrylic plate of uniform thickness exceeded the contrast of the traditional attenuation image by an approximate factor of two. Comparison of the planar phase shift images from a single, uniform thickness polystyrene plate with two polystyrene plates demonstrated an approximate linearity of the estimated phase shift with plate thickness (−1600 rad vs −2970 rad). Tomographic phase shift images of the habanero pepper exhibited acceptable spatial resolution and contrast comparable to the corresponding attenuation image.Conclusions: This work demonstrated the feasibility of laboratory-based phase shift tomosynthesis and suggests that phase shift imaging could potentially provide a new imaging biomarker. Further investigation will be needed to determine if phase shift contrast will be able to provide new tissue contrast information or improved clinical performance.« less

Integrated reactor and centrifugal separator and uses thereof

DOEpatents

Birdwell, Jr., Joseph F; Jennings, Harold L [Clinton, TN; McFarlane, Joanna [Oak Ridge, TN; Tsouris, Constantino [Oak Ridge, TN

2012-01-17

An apparatus for providing reaction of fluids and separation of products with increased residence time. The apparatus includes a stationary shell, a rotating hollow cylindrical component disposed in the stationary shell, a residence-time increasing device external to the stationary shell, a standpipe for introducing fluid into an interior cavity of the hollow cylindrical component from the residence-time increasing device, a first outlet in fluid flow communication with the interior cavity of the hollow cylindrical component for a less dense phase fluid, and a second outlet in fluid flow communication with the interior cavity of the hollow cylindrical component for a more dense phase fluid.

V-shaped resonators for addition of broad-area laser diode arrays

DOEpatents

Liu, Bo; Liu, Yun; Braiman, Yehuda Y.

2012-12-25

A system and method for addition of broad-area semiconductor laser diode arrays are described. The system can include an array of laser diodes, a V-shaped external cavity, and grating systems to provide feedback for phase-locking of the laser diode array. A V-shaped mirror used to couple the laser diode emissions along two optical paths can be a V-shaped prism mirror, a V-shaped stepped mirror or include multiple V-shaped micro-mirrors. The V-shaped external cavity can be a ring cavity. The system can include an external injection laser to further improve coherence and phase-locking.

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

NASA Astrophysics Data System (ADS)

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

2017-02-01

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

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

Akparov, V V; Dmitriev, Valentin G; Duraev, V P

A semiconductor ring laser (SRL) with a radiation wavelength of 1540 nm and a fibre ring cavity is developed and studied in several main lasing regimes. An SRL design based on a semiconductor optical travelling-wave amplifier and a ring cavity, composed of a single-mode polarisation-maintaining fibre, is considered. The SRL is studied in the regime of a rotation speed sensor, in which the frequency shift of counterpropagating waves in the SRL is proportional to its rotation speed. The minimum rotation speed that can be detected using the SRL under consideration depends on the cavity length; in our experiment it turnedmore » to be 1deg s{sup -1}. The changes in the threshold current, emission spectrum, and fundamental radiation wavelength upon closing and opening the SRL ring cavity and with a change in its radius are also investigated. (lasers)« less

Engineering steady-state entanglement via dissipation and quantum Zeno dynamics in an optical cavity.

PubMed

Li, Dong-Xiao; Shao, Xiao-Qiang; Wu, Jin-Hui; Yi, X X

2017-10-01

A new mechanism is proposed for dissipatively preparing maximal Bell entangled state of two atoms in an optical cavity. This scheme integrates the spontaneous emission, the light shift of atoms in the presence of dispersive microwave field, and the quantum Zeno dynamics induced by continuous coupling, to obtain a unique steady state irrespective of initial state. Even for a large cavity decay, a high-fidelity entangled state is achievable at a short convergence time, since the occupation of the cavity mode is inhibited by the Zeno requirement. Therefore, a low single-atom cooperativity C=g 2 /(κγ) is good enough for realizing a high fidelity of entanglement in a wide range of decoherence parameters. As a straightforward extension, the feasibility for preparation of two-atom Knill-Laflamme-Milburn state with the same mechanism is also discussed.

ACTOplus Met XR in Treating Patients With Stage I-IV Oral Cavity or Oropharynx Cancer Undergoing Definitive Treatment | Division of Cancer Prevention

Cancer.gov

This randomized phase IIb trial studies how well ACTOplus met XR works in treating in patients with stage I-IV oral cavity or oropharynx cancer that are undergoing definitive treatment. Chemoprevention is the use of drugs to keep oral cavity or oropharynx cancer from forming or coming back. The use of ACTOplus met XR may slow disease progression in patients with oral cavity or

A microwave cavity for measurement of the mass of hydrogen pellets

NASA Astrophysics Data System (ADS)

Sørensen, H.; Hansen, J. E.; Michelsen, P.; Sass, B.; Weisberg, K.-V.; Knudsen, O.; Michelsen, E.

1990-11-01

A description is given of a nondestructive method utilizing a microwave cavity for measuring the mass of high-speed pellets of solid hydrogen. The cavity is designed for use on a multishot pellet injector, where eight pellets are fired successively with trajectories being parallel and symmetrical around the injector axis. The cavity is cylindrical with the axis coinciding with the injector axis. When a pellet passes through the cavity through holes of 15-16 mm diameter, the change in resonant frequency is proportional to the pellet mass. As a result of the cylindrical symmetry the sensitivity will be identical for all pellets. The frequency shift is measured directly and is converted to a signal proportional to the size of the pellet. The cavity was calibrated with pellets of H2 and D2 containing around 6×1020 atoms and with velocities between 1200 and 1500 m/s. The sensitivity was found to be 300±15 mV/1020 atoms in both cases. This is in fair agreement with estimates made from the dielectric constants of solid H2 and D2. The cavity is built together with two optical detectors for time of flight measurements to form an integrated diagnostic unit.

Imaging the Gouy phase shift in photonic jets with a wavefront sensor.

PubMed

Bon, Pierre; Rolly, Brice; Bonod, Nicolas; Wenger, Jérôme; Stout, Brian; Monneret, Serge; Rigneault, Hervé

2012-09-01

A wavefront sensor is used as a direct observation tool to image the Gouy phase shift in photonic nanojets created by micrometer-sized dielectric spheres. The amplitude and phase distributions of light are found in good agreement with a rigorous electromagnetic computation. Interestingly the observed phase shift when travelling through the photonic jet is a combination of the awaited π Gouy shift and a phase shift induced by the bead refraction. Such direct spatial phase shift observation using wavefront sensors would find applications in microscopy, diffractive optics, optical trapping, and point spread function engineering.

Noise-immune cavity-enhanced optical frequency comb spectroscopy: a sensitive technique for high-resolution broadband molecular detection

NASA Astrophysics Data System (ADS)

Khodabakhsh, Amir; Johansson, Alexandra C.; Foltynowicz, Aleksandra

2015-04-01

Noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS) is a recently developed technique that utilizes phase modulation to obtain immunity to frequency-to-amplitude noise conversion by the cavity modes and yields high absorption sensitivity over a broad spectral range. We describe the principles of the technique and discuss possible comb-cavity matching solutions. We present a theoretical description of NICE-OFCS signals detected with a Fourier transform spectrometer (FTS) and validate the model by comparing it to experimental CO2 spectra around 1,575 nm. Our system is based on an Er:fiber femtosecond laser locked to a cavity and phase-modulated at a frequency equal to a multiple of the cavity free spectral range (FSR). The NICE-OFCS signal is detected by a fast-scanning FTS equipped with a high-bandwidth commercial detector. We demonstrate a simple method of passive locking of the modulation frequency to the cavity FSR that significantly improves the long-term stability of the system, allowing averaging times on the order of minutes. Using a cavity with a finesse of ~9,000, we obtain absorption sensitivity of 6.4 × 10-11 cm-1 Hz-1/2 per spectral element and concentration detection limit for CO2 of 450 ppb Hz-1/2, determined by multiline fitting.

All-optical diode structure based on asymmetrical coupling by a micro-cavity and FP cavity at two sides of photonic crystal waveguide

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

Liu, Bin, E-mail: liubin-d@126.com; Liu, Yun-Feng; He, Xing-Dao

2016-06-15

A high efficiency all-optical diode based on photonic crystal (PC) waveguide has been proposed and numerically investigated by finite-difference time-domain (FDTD) method. The structure is asymmetrically coupled by a micro-cavity containing nonlinear Kerr medium and a FP cavity at sides of PC waveguide. Because of interference between two cavities, Fano peak and FP peak can both appear in transmission spectra and unidirectional transmission can be achieved. The working wavelength can set between two peaks and near to the Fano peak. For forward launch with suitable light intensity, nonlinear Kerr effect of micro-cavity can been excited. It will result in redmore » shift of Fano peak and achieving forward transmission. But for backward launch, a stronger incidence light is needed to the excite Kerr effect due to the design of asymmetric structure. This design has many advantages, including high maximum transmittance, high transmittance contrast ratio, low power threshold, short response time, and ease of integration.« less

The position 68(E11) side chain in myoglobin regulates ligand capture, bond formation with heme iron, and internal movement into the xenon cavities.

PubMed

Dantsker, David; Roche, Camille; Samuni, Uri; Blouin, George; Olson, John S; Friedman, Joel M

2005-11-18

After photodissociation, ligand rebinding to myoglobin exhibits complex kinetic patterns associated with multiple first-order geminate recombination processes occurring within the protein and a simpler bimolecular phase representing second-order ligand rebinding from the solvent. A smooth transition from cryogenic-like to solution phase properties can be obtained by using a combination of sol-gel encapsulation, addition of glycerol as a bathing medium, and temperature tuning (-15 --> 65 degrees C). This approach was applied to a series of double mutants, myoglobin CO (H64L/V68X, where X = Ala, Val, Leu, Asn, and Phe), which were designed to examine the contributions of the position 68(E11) side chain to the appearance and disappearance of internal rebinding phases in the absence of steric and polar interactions with the distal histidine. Based on the effects of viscosity, temperature, and the stereochemistry of the E11 side chain, the three major phases, B --> A, C --> A, and D --> A, can be assigned, respectively, to ligand rebinding from the following: (i) the distal heme pocket, (ii) the xenon cavities prior to large amplitude side chain conformational relaxation, and (iii) the xenon cavities after significant conformational relaxation of the position 68(E11) side chain. The relative amplitudes of the B --> A and C --> A phases depend markedly on the size and shape of the E11 side chain, which regulates sterically both ligand return to the heme iron atom and ligand migration to the xenon cavities. The internal xenon cavities provide a transient docking site that allows side chain relaxations and the entry of water into the vacated distal pocket, which in turn slows ligand recombination markedly.

Microwave differential dilatometer measures 10 - 12 m, at 1 Hz

NASA Astrophysics Data System (ADS)

Aschero, G.; Mango, F.; Gizdulich, P.

1996-12-01

To check and measure the converse piezoelectric effect in bone samples, we had to detect displacements in the range of 1-100 pm with three kinds of restrictions: (1) the biological nature of the samples imposes severe limits in selecting a suitable device and method; (2) such a method has to take into account some clinical applications to which the experiment is devoted; (3) the piezoelectric behavior of bone samples is particularly interesting at low frequencies, around 1 Hz. For such reasons we modified an existing dilatometer based on a microwave differential spectrometer. A 14 GHz klystron, linearly modulated in frequency by a triangular 50 Hz voltage applied to the repeller, is connected, via magic T, to two identical cavities tunable around 14 GHz and whose resonance curves are recorded by crystal detectors. When one of the two cavities changes its height according to the length variations of the sample, its resonance frequency varies resulting in a shift of the resonant curve with respect to the resonance curve of the other cavity acting as reference. The comparison between the cavities' responses is performed by a pulse technique transforming the frequency shifts into time intervals, that are then converted into dc voltages. The differential character of this measurement avoids the need for the microwave source stabilization. The relative shift in frequency is measured with an accuracy better than 500 Hz. This accuracy allows us to measure displacements smaller than 7 nm in the cavity's height. After 2 h of warmup, thanks to the differential arrangement of the system, thermal or other drifts are not detectable within a lapse of time of 12 h. This feature allows coherent signal averaging over long periods. With a piezoelectric ceramic stack moving 100 pm in square wave fashion at 50 mHz we found that the signal to noise ratio was 20 dB after 1000 cycles of signal averaging, when our bandpass filter was tuned at 1 Hz. In conclusion, this system can detect periodic displacements as small as 1 pm in a short time and reliably. Due to the operational simplicity and stability, at room temperature and humidity, the device is suitable for dilatometric measurements on biological samples.

Coherent control of the Goos-Hänchen shift via Fano interference

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

Liu, Shaopeng; Yang, Wen-Xing, E-mail: wenxingyang@seu.edu.cn; Zhu, Zhonghu

2016-04-14

A scheme of enhanced Goos-Hänchen (GH) shifts in reflected and transmitted light beams is exploited in a cavity, where an asymmetric double AlGaAs/GaAs quantum well structure with resonant tunneling to a common continuum is employed as the intracavity medium. With the help of Fano-type interference induced by resonant tunneling, the generated GH shifts that contain a negative lateral shift in reflected light beam and a positive lateral shift in transmitted light beam are found to be significantly enhanced. More interestingly, these GH shifts in reflected and transmitted light beams are modulated by means of a control beam and external biasmore » voltage, in which maximum negative shift of 1.86 mm and positive shift of 0.37 mm are achievable.« less

Asymptotic entanglement dynamics phase diagrams for two electromagnetic field modes in a cavity

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

Drumond, R. C.; Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Boltzmanngasse 3, Vienna; Souza, L. A. M.

We investigate theoretically an open dynamics for two modes of electromagnetic field inside a microwave cavity. The dynamics is Markovian and determined by two types of reservoirs: the ''natural'' reservoirs due to dissipation and temperature of the cavity, and an engineered one, provided by a stream of atoms passing trough the cavity, as devised by Pielawa et al. [Phys. Rev. Lett. 98, 240401 (2007)]. We found that, depending on the reservoir parameters, the system can have distinct ''phases'' for the asymptotic entanglement dynamics: it can disentangle at finite time or it can have persistent entanglement for large times, with themore » transition between them characterized by the possibility of asymptotical disentanglement. Incidentally, we also discuss the effects of dissipation on the scheme proposed in the above reference for generation of entangled states.« less

Large-Grain Superconducting Gun Cavity Testing Program Phase One Closing Report

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

Hammons, L.; Bellavia, S.; Belomestnykh, S.

2013-10-31

This report details the experimental configuration and RF testing results for the first phase of a large-grained niobium electron gun cavity testing program being conducted in the Small Vertical Testing Facility in the Collider-Accelerator Department. This testing is meant to explore multi-pacting in the cavity and shed light on the behavior of a counterpart cavity of identical geometry installed in the Energy Recovery LINAC being constructed in the Collider-Accelerator Department at Brookhaven National Laboratory. This test found that the Q of the large-grained cavity at 4 K reached ~6.5 × 10 8 and at 2 K reached a value ofmore » ~6 × 10 9. Both of these values are about a factor of 10 lower than would be expected for this type of cavity given the calculated surface resistance and the estimated geometry factor for this half-cell cavity. In addition, the cavity reached a peak voltage of 0.6 MV before there was sig-nificant decline in the Q value and a substantial increase in field emission. This relatively low volt-age, coupled with the low Q and considerable field emission suggest contamination of the cavity interior, possibly during experimental assembly. The results may also suggest that additional chemical etching of the interior surface of the cavity may be beneficial. Throughout the course of testing, various challenges arose including slow helium transfer to the cryostat and cable difficulties. These difficulties and others were eventually resolved, and the re-port discusses the operating experience of the experiment thus far and the plans for future work aimed at exploring the nature of multipacting with a copper cathode inserted into the cavity.« less

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

Zhu, Meng-Zheng; School of Physics and Electronic Information, Huaibei Normal University, Huaibei 235000; Ye, Liu, E-mail: yeliu@ahu.edu.cn

An efficient scheme is proposed to implement phase-covariant quantum cloning by using a superconducting transmon qubit coupled to a microwave cavity resonator in the strong dispersive limit of circuit quantum electrodynamics (QED). By solving the master equation numerically, we plot the Wigner function and Poisson distribution of the cavity mode after each operation in the cloning transformation sequence according to two logic circuits proposed. The visualizations of the quasi-probability distribution in phase-space for the cavity mode and the occupation probability distribution in the Fock basis enable us to penetrate the evolution process of cavity mode during the phase-covariant cloning (PCC)more » transformation. With the help of numerical simulation method, we find out that the present cloning machine is not the isotropic model because its output fidelity depends on the polar angle and the azimuthal angle of the initial input state on the Bloch sphere. The fidelity for the actual output clone of the present scheme is slightly smaller than one in the theoretical case. The simulation results are consistent with the theoretical ones. This further corroborates our scheme based on circuit QED can implement efficiently PCC transformation.« less

End plate assembly having a two-phase fluid-filled bladder and method for compressing a fuel cell stack

DOEpatents

Carlstrom, Jr., Charles M.

2001-01-01

An end plate assembly is disclosed for use in a fuel cell assembly in which the end plate assembly includes a housing having a cavity, and a bladder receivable in the cavity and engageable with the fuel cell stack. The bladder includes a two-phase fluid having a liquid portion and a vapor portion. Desirably, the two-phase fluid has a vapor pressure between about 100 psi and about 600 psi at a temperature between about 70 degrees C. to about 110 degrees C.

Fiber optic microphone with large dynamic range based on bi-fiber Fabry-Perot cavity

NASA Astrophysics Data System (ADS)

Cheng, Jin; Lu, Dan-feng; Gao, Ran; Qi, Zhi-mei

2017-10-01

In this paper, we report a fiber optic microphone with a large dynamic range. The probe of microphone consists of bi-fiber Fabry-Perot cavity architecture. The wavelength of the working laser is about 1552.05nm. At this wavelength, the interference spectroscopies of these two fiber Fabry-Perot cavities have a quadrature shift. So the outputs of these two fiber Fabry-Perot sensors are orthogonal signal. By using orthogonal signal demodulation method, this microphone can output a signal of acoustic wave. Due to no relationship between output signal and the linear region on interference spectroscopy, the microphones have a large maximum acoustic pressure above 125dB.

PSK Shift Timing Information Detection Using Image Processing and a Matched Filter

DTIC Science & Technology

2009-09-01

phase shifts are enhanced.  Develop, design, and test the resulting phase shift identification scheme. xx  Develop, design, and test an optional...and the resulting phase shift identification algorithm is investigated for SNR levels in the range -2dB to 12 dB. Detection performances are derived...test the resulting phase shift identification scheme.  Develop, design, and test an optional analysis window overlapping technique to improve phase

Compact multilayer film structure for angle insensitive color filtering.

PubMed

Yang, Chenying; Shen, Weidong; Zhang, Yueguang; Li, Kan; Fang, Xu; Zhang, Xing; Liu, Xu

2015-03-19

Here we report a compact multilayer film structure for angle robust color filtering, which is verified by theoretical calculations and experiment results. The introduction of the amorphous silicon in the proposed unsymmetrical resonant cavity greatly reduces the angular sensitivity of the filters, which is confirmed by the analysis of the phase shift within the structure. The temperature of the substrate during the deposition is expressly investigated to obtain the best optical performance with high peak reflectance and good angle insensitive color filtering by compromising the refractive index of dielectric layer and the surface roughness of the multilayer film. And the outlayer of the structure, worked as the anti-reflection layer, have an enormous impact on the filtering performance. This method, described in this paper, can have enormous potential for diverse applications in display, colorful decoration, anti-counterfeiting and so forth.

Alternating phase-shifted mask for logic gate levels, design, and mask manufacturing

NASA Astrophysics Data System (ADS)

Liebmann, Lars W.; Graur, Ioana C.; Leipold, William C.; Oberschmidt, James M.; O'Grady, David S.; Regaill, Denis

1999-07-01

While the benefits of alternating phase shifted masks in improving lithographic process windows at increased resolution are well known throughout the lithography community, broad implementation of this potentially powerful technique has been slow due to the inherent complexity of the layout design and mask manufacturing process. This paper will review a project undertaken at IBM's Semiconductor Research and Development Center and Mask Manufacturing and Development facility to understand the technical and logistical issues associated with the application of alternating phase shifted mask technology to the gate level of a full microprocessor chip. The work presented here depicts an important milestone toward integration of alternating phase shifted masks into the manufacturing process by demonstrating an automated design solution and yielding a functional alternating phase shifted mask. The design conversion of the microprocessor gate level to a conjugate twin shifter alternating phase shift layout was accomplished with IBM's internal design system that automatically scaled the design, added required phase regions, and resolved phase conflicts. The subsequent fabrication of a nearly defect free phase shifted mask, as verified by SEM based die to die inspection, highlights the maturity of the alternating phase shifted mask manufacturing process in IBM's internal mask facility. Well defined and recognized challenges in mask inspection and repair remain and the layout of alternating phase shifted masks present a design and data preparation overhead, but the data presented here demonstrate the feasibility of designing and building manufacturing quality alternating phase shifted masks for the gate level of a microprocessor.

Implementing an ancilla-free 1→M economical phase-covariant quantum cloning machine with superconducting quantum-interference devices in cavity QED

NASA Astrophysics Data System (ADS)

Yu, Long-Bao; Zhang, Wen-Hai; Ye, Liu

2007-09-01

We propose a simple scheme to realize 1→M economical phase-covariant quantum cloning machine (EPQCM) with superconducting quantum interference device (SQUID) qubits. In our scheme, multi-SQUIDs are fixed into a microwave cavity by adiabatic passage for their manipulation. Based on this model, we can realize the EPQCM with high fidelity via adiabatic quantum computation.

New auto-tuning technique for the hydrogen maser

NASA Technical Reports Server (NTRS)

Sydnor, R. L.; Maleki, L.

1983-01-01

Auto-tuning of the maser cavity compensates for cavity pulling effect, and other sources of contribution to the long term frequency drift. Schemes previously proposed for the maser cavity auto-tuning can have adverse effects on the performance of the maser. A new scheme is proposed based on the phase relationship between the electric and the magnetic fields inside the cavity. This technique has the desired feature of auto-tuning the cavity with a very high sensitivity and without disturbing the maser performance. Some approaches for the implementation of this scheme and possible areas of difficulty are examined.

Soliton-dark pulse pair formation in birefringent cavity fiber lasers through cross phase coupling.

PubMed

Shao, Guodong; Song, Yufeng; Zhao, Luming; Shen, Deyuan; Tang, Dingyuan

2015-10-05

We report on the experimental observation of soliton-dark pulse pair formation in a birefringent cavity fiber laser. Temporal cavity solitons are formed in one polarization mode of the cavity. It is observed that associated with each of the cavity solitons a dark pulse is induced on the CW background of the orthogonal polarization mode. We show that the dark pulse formation is a result of the incoherent cross polarization coupling between the soliton and the CW beam and has a mechanism similar to that of the polarization domain formation observed in the fiber lasers.

Nanostructures formed by cyclodextrin covered procainamide through supramolecular self assembly - Spectral and molecular modeling study

NASA Astrophysics Data System (ADS)

Rajendiran, N.; Mohandoss, T.; Sankaranarayanan, R. K.

2015-02-01

Inclusion complexation behavior of procainamide (PCA) with two cyclodextrins (α-CD and β-CD) were analyzed by absorption, fluorescence, scanning electron microscope (SEM), transmission electron microscope (TEM), Raman image, FT-IR, differential scanning colorimeter (DSC), Powder X ray diffraction (XRD) and 1H NMR. Blue shift was observed in β-CD whereas no significant spectral shift observed in α-CD. The inclusion complex formation results suggest that water molecules also present in the inside of the CD cavity. The present study revealed that the phenyl ring of the PCA drug is entrapped in the CD cavity. Cyclodextrin studies show that PCA forms 1:2 inclusion complex with α-CD and β-CD. PCA:α-CD complex form nano-sized particles (46 nm) and PCA:β-CD complex form self-assembled to micro-sized tubular structures. The shape-shifting of 2D nanosheets into 1D microtubes by simple rolling mechanism were analysed by micro-Raman and TEM images. Thermodynamic parameters (ΔH, ΔG and ΔS) of inclusion process were determined from semiempirical PM3 calculations.

Effect of Phase Shift from Corals to Zoantharia on Reef Fish Assemblages

PubMed Central

Cruz, Igor C. S.; Loiola, Miguel; Albuquerque, Tiago; Reis, Rodrigo; de Anchieta C. C. Nunes, José; Reimer, James D.; Mizuyama, Masaru; Kikuchi, Ruy K. P.; Creed, Joel C.

2015-01-01

Consequences of reef phase shifts on fish communities remain poorly understood. Studies on the causes, effects and consequences of phase shifts on reef fish communities have only been considered for coral-to-macroalgae shifts. Therefore, there is a large information gap regarding the consequences of novel phase shifts and how these kinds of phase shifts impact on fish assemblages. This study aimed to compare the fish assemblages on reefs under normal conditions (relatively high cover of corals) to those which have shifted to a dominance of the zoantharian Palythoa cf. variabilis on coral reefs in Todos os Santos Bay (TSB), Brazilian eastern coast. We examined eight reefs, where we estimated cover of corals and P. cf. variabilis and coral reef fish richness, abundance and body size. Fish richness differed significantly between normal reefs (48 species) and phase-shift reefs (38 species), a 20% reduction in species. However there was no difference in fish abundance between normal and phase shift reefs. One fish species, Chaetodon striatus, was significantly less abundant on normal reefs. The differences in fish assemblages between different reef phases was due to differences in trophic groups of fish; on normal reefs carnivorous fishes were more abundant, while on phase shift reefs mobile invertivores dominated. PMID:25629532

Plasma influence on the dispersion properties of finite-length, corrugated waveguides

NASA Astrophysics Data System (ADS)

Shkvarunets, A.; Kobayashi, S.; Weaver, J.; Carmel, Y.; Rodgers, J.; Antonsen, T. M., Jr.; Granatstein, V. L.; Destler, W. W.; Ogura, K.; Minami, K.

1996-03-01

We present an experimental study of the electromagnetic properties of transverse magnetic modes in a corrugated-wall cavity filled with a radially inhomogeneous plasma. The shifts of the resonant frequencies of a finite-length, corrugated cavity were measured as a function of the background plasma density and the dispersion diagram was reconstructed up to a peak plasma density of 1012 cm-3. Good agreement with a calculated dispersion diagram is obtained for plasma densities below 5×1011 cm-3.

Experimental observation of a large low-frequency band gap in a polymer waveguide

NASA Astrophysics Data System (ADS)

Miniaci, Marco; Mazzotti, Matteo; Radzieński, Maciej; Kherraz, Nesrine; Kudela, Pawel; Ostachowicz, Wieslaw; Morvan, Bruno; Bosia, Federico; Pugno, Nicola M.

2018-02-01

The quest for large and low frequency band gaps is one of the principal objectives pursued in a number of engineering applications, ranging from noise absorption to vibration control, to seismic wave abatement. For this purpose, a plethora of complex architectures (including multi-phase materials) and multi-physics approaches have been proposed in the past, often involving difficulties in their practical realization. To address this issue, in this work we propose an easy-to-manufacture design able to open large, low frequency complete Lamb band gaps exploiting a suitable arrangement of masses and stiffnesses produced by cavities in a monolithic material. The performance of the designed structure is evaluated by numerical simulations and confirmed by Scanning Laser Doppler Vibrometer (SLDV) measurements on an isotropic polyvinyl chloride plate in which a square ring region of cross-like cavities is fabricated. The full wave field reconstruction clearly confirms the ability of even a limited number of unit cell rows of the proposed design to efficiently attenuate Lamb waves. In addition, numerical simulations show that the structure allows to shift of the central frequency of the BG through geometrical modifications. The design may be of interest for applications in which large BGs at low frequencies are required.

Characteristic vibration patterns of odor compounds from bread-baking volatiles upon protein binding: density functional and ONIOM study and principal component analysis.

PubMed

Treesuwan, Witcha; Hirao, Hajime; Morokuma, Keiji; Hannongbua, Supa

2012-05-01

As the mechanism underlying the sense of smell is unclear, different models have been used to rationalize structure-odor relationships. To gain insight into odorant molecules from bread baking, binding energies and vibration spectra in the gas phase and in the protein environment [7-transmembrane helices (7TMHs) of rhodopsin] were calculated using density functional theory [B3LYP/6-311++G(d,p)] and ONIOM [B3LYP/6-311++G(d,p):PM3] methods. It was found that acetaldehyde ("acid" category) binds strongly in the large cavity inside the receptor, whereas 2-ethyl-3-methylpyrazine ("roasted") binds weakly. Lys296, Tyr268, Thr118 and Ala117 were identified as key residues in the binding site. More emphasis was placed on how vibrational frequencies are shifted and intensities modified in the receptor protein environment. Principal component analysis (PCA) suggested that the frequency shifts of C-C stretching, CH(3) umbrella, C = O stretching and CH(3) stretching modes have a significant effect on odor quality. In fact, the frequency shifts of the C-C stretching and C = O stretching modes, as well as CH(3) umbrella and CH(3) symmetric stretching modes, exhibit different behaviors in the PCA loadings plot. A large frequency shift in the CH(3) symmetric stretching mode is associated with the sweet-roasted odor category and separates this from the acid odor category. A large frequency shift of the C-C stretching mode describes the roasted and oily-popcorn odor categories, and separates these from the buttery and acid odor categories.

Multi-Mode Cavity Accelerator Structure

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

Jiang, Yong; Hirshfield, Jay Leonard

2016-11-10

This project aimed to develop a prototype for a novel accelerator structure comprising coupled cavities that are tuned to support modes with harmonically-related eigenfrequencies, with the goal of reaching an acceleration gradient >200 MeV/m and a breakdown rate <10 -7/pulse/meter. Phase I involved computations, design, and preliminary engineering of a prototype multi-harmonic cavity accelerator structure; plus tests of a bimodal cavity. A computational procedure was used to design an optimized profile for a bimodal cavity with high shunt impedance and low surface fields to maximize the reduction in temperature rise ΔT. This cavity supports the TM010 mode and its 2ndmore » harmonic TM011 mode. Its fundamental frequency is at 12 GHz, to benchmark against the empirical criteria proposed within the worldwide High Gradient collaboration for X-band copper structures; namely, a surface electric field E sur max< 260 MV/m and pulsed surface heating ΔT max< 56 °K. With optimized geometry, amplitude and relative phase of the two modes, reductions are found in surface pulsed heating, modified Poynting vector, and total RF power—as compared with operation at the same acceleration gradient using only the fundamental mode.« less

Quantum Phase Transitions in Cavity Coupled Dot systems

NASA Astrophysics Data System (ADS)

Kasisomayajula, Vijay; Russo, Onofrio

2011-03-01

We investigate a Quantum Dot System, in which the transconductance, in part, is due to spin coupling, with each dot subjected to a biasing voltage. When this system is housed in a QED cavity, the cavity dot coupling alters the spin coupling of the coupled dots significantly via the Purcell Effect. In this paper we show the extent to which one can control the various coupling parameters: the inter dot coupling, the individual dots coupling with the cavity and the coupled dots coupling with the cavity as a single entity. We show that the dots coupled to each other and to the cavity, the spin transport can be controlled selectively. We derive the conditions for such control explicitly. Further, we discuss the Quantum phase transition effects due to the charge and spin transport through the dots. The electron transport through the dots, electron-electron spin interaction and the electron-photon interaction are treated using the Non-equilibrium Green's Function Formalism. http://publish.aps.org/search/field/author/Trif_Mircea (Trif Mircea), http://publish.aps.org/search/field/author/Golovach_Vitaly_N (Vitaly N. Golovach), and http://publish.aps.org/search/field/author/Loss_Daniel (Daniel Loss), Phys. Rev. B 75, 085307 (2007)

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

Langridge, Justin M.; Shillings, Alexander J. L.; Jones, Roderic L.

A broadband absorption spectrometer has been developed for highly sensitive and target-selective in situ trace gas measurements. The instrument employs two distinct modes of operation: (i) broadband cavity enhanced absorption spectroscopy (BBCEAS) is used to quantify the concentration of gases in sample mixtures from their characteristic absorption features, and (ii) periodic measurements of the cavity mirrors' reflectivity are made using step-scan phase shift cavity ringdown spectroscopy (PSCRDS). The latter PSCRDS method provides a stand-alone alternative to the more usual method of determining mirror reflectivities by measuring BBCEAS absorption spectra for calibration samples of known composition. Moreover, the instrument's two modesmore » of operation use light from the same light emitting diode transmitted through the cavity in the same optical alignment, hence minimizing the potential for systematic errors between mirror reflectivity determinations and concentration measurements. The ability of the instrument to quantify absorber concentrations is tested in instrument intercomparison exercises for NO{sub 2} (versus a laser broadband cavity ringdown spectrometer) and for H{sub 2}O (versus a commercial hygrometer). A method is also proposed for calculating effective absorption cross sections for fitting the differential structure in BBCEAS spectra due to strong, narrow absorption lines that are under-resolved and hence exhibit non-Beer-Lambert law behavior at the resolution of the BBCEAS measurements. This approach is tested on BBCEAS spectra of water vapor's 4v+{delta} absorption bands around 650 nm. The most immediate analytical application of the present instrument is in quantifying the concentration of reactive trace gases in the ambient atmosphere. The instrument's detection limits for NO{sub 3} as a function of integration time are considered in detail using an Allan variance analysis. Experiments under laboratory conditions produce a 1{sigma} detection limit of 0.25 pptv for a 10 s acquisition time, which improves with further signal averaging to 0.09 pptv in 400 s. Finally, an example of the instrument's performance under field work conditions is presented, in this case of measurements of the sum of NO{sub 3}+N{sub 2}O{sub 5} concentrations in the marine boundary layer acquired during the Reactive Halogens in the Marine Boundary Layer field campaign.« less

Circular carrier squeezing interferometry: Suppressing phase shift error in simultaneous phase-shifting point-diffraction interferometer

NASA Astrophysics Data System (ADS)

Zheng, Donghui; Chen, Lei; Li, Jinpeng; Sun, Qinyuan; Zhu, Wenhua; Anderson, James; Zhao, Jian; Schülzgen, Axel

2018-03-01

Circular carrier squeezing interferometry (CCSI) is proposed and applied to suppress phase shift error in simultaneous phase-shifting point-diffraction interferometer (SPSPDI). By introducing a defocus, four phase-shifting point-diffraction interferograms with circular carrier are acquired, and then converted into linear carrier interferograms by a coordinate transform. Rearranging the transformed interferograms into a spatial-temporal fringe (STF), so the error lobe will be separated from the phase lobe in the Fourier spectrum of the STF, and filtering the phase lobe to calculate the extended phase, when combined with the corresponding inverse coordinate transform, exactly retrieves the initial phase. Both simulations and experiments validate the ability of CCSI to suppress the ripple error generated by the phase shift error. Compared with carrier squeezing interferometry (CSI), CCSI is effective on some occasions in which a linear carrier is difficult to introduce, and with the added benefit of eliminating retrace error.

Progress towards a cesium atomic fountain clock

NASA Astrophysics Data System (ADS)

Klipstein, William M.; Raithel, Georg A.; Rolston, Steven L.; Phillips, William D.; Ekstrom, Christopher R.

1997-04-01

We have been developing a fountain of laser--cooled cesium atoms for use as an atomic clock. Our design largely follows that of the fountain built at LPTF in Paris. In our fountain, chirp--slowed atoms are first collected in a Magneto--Optic Trap (MOT) and then cooled to a few μK in optical molasses. The cooled atoms are then launched vertically into a "moving molasses" by shifting the frequencies of the vertical cooling beams. The atoms then travel through a microwave cavity tuned to the 9.2 GHz cesium hyperfine frequency for a first Ramsey pulse. After roughly 0.5 seconds of free flight under the influence of gravity, the atoms fall back through the microwave cavity and into an optical state--detection region which detects the number of atoms making the F=3 arrow F=4 transition. The increased Ramsey interaction time improves the short--time precision as compared to traditional atomic beam experiments, while many systematic shifts which limit the accuracy of an atomic beam clock are reduced by the low atomic velocity and the retrace of the atomic trajectory through the microwave cavity. We will discuss the progress towards a working fountain being assembled in our laboratory.

How Much Binding Affinity Can be Gained by Filling a Cavity?

PubMed Central

Kawasaki, Yuko; Chufan, Eduardo E.; Lafont, Virginie; Hidaka, Koushi; Kiso, Yoshiaki; Amzel, L. Mario; Freire, Ernesto

2011-01-01

Binding affinity optimization is critical during drug development. Here we evaluate the thermodynamic consequences of filling a binding cavity with functionalities of increasing van der Waals radii (-H, -F, -Cl and CH3) that improve the geometric fit without participating in hydrogen bonding or other specific interactions. We observe a binding affinity increase of two orders of magnitude. There appears to be three phases in the process. The first phase is associated with the formation of stable van der Waals interactions. This phase is characterized by a gain in binding enthalpy and a loss in binding entropy, attributed to a loss of conformational degrees of freedom. For the specific case presented in this paper, the enthalpy gain amounts to −1.5 kcal/mol while the entropic losses amount to +0.9 kcal/mol resulting in a net 3.5-fold affinity gain. The second phase is characterized by simultaneous enthalpic and entropic gains. This phase improves the binding affinity 25-fold. The third phase represents the collapse of the trend and is triggered by the introduction of chemical functionalities larger than the binding cavity itself (CH(CH3)2). It is characterized by large enthalpy and affinity losses. The thermodynamic signatures associated with each phase provide guidelines for lead optimization. PMID:20028396

An NMR-Based Structural Rationale for Contrasting Stoichiometry and Ligand Binding Site(s) in Fatty Acid-binding Proteins†

PubMed Central

He, Yan; Estephan, Rima; Yang, Xiaomin; Vela, Adriana; Wang, Hsin; Bernard, Cédric; Stark, Ruth E.

2011-01-01

Liver fatty acid-binding protein (LFABP) is a 14-kDa cytosolic polypeptide, differing from other family members in number of ligand binding sites, diversity of bound ligands, and transfer of fatty acid(s) to membranes primarily via aqueous diffusion rather than direct collisional interactions. Distinct two-dimensional 1H-15N NMR signals indicative of slowly exchanging LFABP assemblies formed during stepwise ligand titration were exploited, without solving the protein-ligand complex structures, to yield the stoichiometries for the bound ligands, their locations within the protein binding cavity, the sequence of ligand occupation, and the corresponding protein structural accommodations. Chemical shifts were monitored for wild-type LFABP and a R122L/S124A mutant in which electrostatic interactions viewed as essential to fatty acid binding were removed. For wild-type LFABP the results compared favorably with previous tertiary structures of oleate-bound wild-type LFABP in crystals and in solution: there are two oleates, one U-shaped ligand that positions the long hydrophobic chain deep within the cavity and another extended structure with the hydrophobic chain facing the cavity and the carboxylate group lying close to the protein surface. The NMR titration validated a prior hypothesis that the first oleate to enter the cavity occupies the internal protein site. In contrast, 1H/15N chemical shift changes supported only one liganded oleate for R122L/S124A LFABP, at an intermediate location within the protein cavity. A rationale based on protein sequence and electrostatics was developed to explain the stoichiometry and binding site trends for LFABPs and to put these findings into context within the larger protein family. PMID:21226535

Method for maximizing the brightness of the bunches in a particle injector by converting a highly space-charged beam to a relativistic and emittance-dominated beam

DOEpatents

Hannon, Fay

2016-08-02

A method for maximizing the brightness of the bunches in a particle injector by converting a highly space-charged beam to a relativistic and emittance-dominated beam. The method includes 1) determining the bunch charge and the initial kinetic energy of the highly space-charge dominated input beam; 2) applying the bunch charge and initial kinetic energy properties of the highly space-charge dominated input beam to determine the number of accelerator cavities required to accelerate the bunches to relativistic speed; 3) providing the required number of accelerator cavities; and 4) setting the gradient of the radio frequency (RF) cavities; and 5) operating the phase of the accelerator cavities between -90 and zero degrees of the sinusoid of phase to simultaneously accelerate and bunch the charged particles to maximize brightness, and until the beam is relativistic and emittance-dominated.

Cavity approach to noisy learning in nonlinear perceptrons.

PubMed

Luo, P; Michael Wong, K Y

2001-12-01

We analyze the learning of noisy teacher-generated examples by nonlinear and differentiable student perceptrons using the cavity method. The generic activation of an example is a function of the cavity activation of the example, which is its activation in the perceptron that learns without the example. Mean-field equations for the macroscopic parameters and the stability condition yield results consistent with the replica method. When a single value of the cavity activation maps to multiple values of the generic activation, there is a competition in learning strategy between preferentially learning an example and sacrificing it in favor of the background adjustment. We find parameter regimes in which examples are learned preferentially or sacrificially, leading to a gap in the activation distribution. Full phase diagrams of this complex system are presented, and the theory predicts the existence of a phase transition from poor to good generalization states in the system. Simulation results confirm the theoretical predictions.

A hybrid six-dimensional muon cooling channel using gas filled rf cavities

DOE PAGES

Stratakis, D.

2017-09-25

We describe an alternative cooling approach to prevent rf breakdown in magnetic fields that simultaneously reduces all six phase-space dimensions of a muon beam. In this process, cooling is accomplished by reducing the beam momentum through ionization energy loss in discrete absorbers and replenishing the momentum loss only in the longitudinal direction through gas-filled rf cavities. The advantage of gas filled cavities is that they can run at high gradients in magnetic fields without breakdown. Using this approach, we show that our channel can achieve a decrease of the 6-dimensional phase-space volume by several orders of magnitude. With the aidmore » of numerical simulations, we demonstrate that the transmission of our proposed channel is comparable to that of an equivalent channel with vacuum rf cavities. Finally, we discuss the sensitivity of the channel performance to the choice of gas and operating pressure.« less

A hybrid six-dimensional muon cooling channel using gas filled rf cavities

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

Stratakis, D.

We describe an alternative cooling approach to prevent rf breakdown in magnetic fields that simultaneously reduces all six phase-space dimensions of a muon beam. In this process, cooling is accomplished by reducing the beam momentum through ionization energy loss in discrete absorbers and replenishing the momentum loss only in the longitudinal direction through gas-filled rf cavities. The advantage of gas filled cavities is that they can run at high gradients in magnetic fields without breakdown. Using this approach, we show that our channel can achieve a decrease of the 6-dimensional phase-space volume by several orders of magnitude. With the aidmore » of numerical simulations, we demonstrate that the transmission of our proposed channel is comparable to that of an equivalent channel with vacuum rf cavities. Finally, we discuss the sensitivity of the channel performance to the choice of gas and operating pressure.« less

Interference effects in a cavity for optical amplification

NASA Astrophysics Data System (ADS)

Cardimona, D. A.; Alsing, P. M.

2009-08-01

In space situational awareness scenarios, the objects needed to be characterized and identified are usually quite far away and quite dim. Thus, optical detectors need to be able to sense these very dim optical signals. Quantum interference in a three-level system can lead to amplification of optical signals. If we put a three-level system into a cavity tuned to the frequency of an incoming optical signal, we anticipate the amplification possibilities should be increased proportional to the quality factor of the cavity. Our vision is to utilize quantum dots in photonic crystal cavities, but as a stepping stone we first investigate a simple three-level system in a free-space optical cavity. We investigate quantum interference and classical interference effects when a three-level system interacts with both a cavity field mode and an external driving field mode. We find that under certain circumstances the cavity field evolves to be equal in magnitude to, but 180° out-of-phase with the external pump field when the pump field frequency equals the cavity frequency. At this point the resonance fluorescence from the atom in the cavity goes to zero due to a purely classical interference effect between the two out-of-phase fields. This is quite different from the quantum interference that occurs under the right circumstances, when the state populations are coherently driven into a linear combination that is decoupled from any applied field - and population is trapped in the excited states, thus allowing for a population inversion and an amplification of incoming optical signals.

Ferruleless coupled-cavity traveling-wave tube cold-test characteristics simulated with micro-SOS

NASA Technical Reports Server (NTRS)

Schroeder, Dana L.; Wilson, Jeffrey D.

1993-01-01

The three-dimensional, electromagnetic circuit analysis code, Micro-SOS, can be used to reduce expensive and time consuming experimental 'cold-testing' of traveling-wave tube (TWT) circuits. The frequency-phase dispersion and beam interaction impedance characteristics of a ferruleless coupled-cavity traveling-wave tube slow-wave circuit were simulated using the code. Computer results agree closely with experimental data. Variations in the cavity geometry dimensions of period length and gap-to-period ratio were modeled. These variations can be used in velocity taper designs to reduce the radiofrequency (RF) phase velocity in synchronism with the decelerating electron beam. Such circuit designs can result in enhanced TWT power and efficiency.

Quantitative phase imaging of human red blood cells using phase-shifting white light interference microscopy with colour fringe analysis

NASA Astrophysics Data System (ADS)

Singh Mehta, Dalip; Srivastava, Vishal

2012-11-01

We report quantitative phase imaging of human red blood cells (RBCs) using phase-shifting interference microscopy. Five phase-shifted white light interferograms are recorded using colour charge coupled device camera. White light interferograms were decomposed into red, green, and blue colour components. The phase-shifted interferograms of each colour were then processed by phase-shifting analysis and phase maps for red, green, and blue colours were reconstructed. Wavelength dependent refractive index profiles of RBCs were computed from the single set of white light interferogram. The present technique has great potential for non-invasive determination of refractive index variation and morphological features of cells and tissues.

Mid-Infrared Tunable Resonant Cavity Enhanced Detectors

PubMed Central

Quack, Niels; Blunier, Stefan; Dual, Jurg; Felder, Ferdinand; Arnold, Martin; Zogg, Hans

2008-01-01

Mid-infrared detectors that are sensitive only in a tunable narrow spectral band are presented. They are based on the Resonant Cavity Enhanced Detector (RCED) principle and employing a thin active region using IV-VI narrow gap semiconductor layers. A Fabry-Pérot cavity is formed by two mirrors. The active layer is grown onto one mirror, while the second mirror can be displaced. This changes the cavity length thus shifting the resonances where the detector is sensitive. Using electrostatically actuated MEMS micromirrors, a very compact tunable detector system has been fabricated. Mirror movements of more than 3 μm at 30V are obtained. With these mirrors, detectors with a wavelength tuning range of about 0.7 μm have been realized. Single detectors can be used in mid-infrared micro spectrometers, while a detector arrangement in an array makes it possible to realize Adaptive Focal Plane Arrays (AFPA). PMID:27873824

Microwave Resonant Cavity and Loaded Carbon Nanotubes -- A Sensor to Detect Toxins like Methamphetamine

NASA Astrophysics Data System (ADS)

Anand, Aman; Robert, James; Henley, Don; Dahiya, Jai

2006-10-01

A resonant cavity operating in TM010 mode was used to study the absorption response of Single Walled Carbon Nanotubes and other Nanomaterials for different types of gas molecules. The range of the frequency signal as a probe was chosen arbitrarily between 9.1 -9.8 GHz. A highly specific range will be studied for further experiments. It was found that for different pressures of different gases and different types of Nanomaterials, there was a different response in the shifts of the probe signal for each cycle of gassing and degassing of the cavity. The preliminary work done so far suggests that Microwave spectroscopy of the complex medium of gases and Carbon Nanotubes can be used as a highly sensitive technique in studying the complex dielectric response of different polar as well as non-polar gases when subjected to intense electromagnetic fields within the Cavity.

Fiber ring laser sensor based on Fabry-Perot cavity interferometer for temperature sensing

NASA Astrophysics Data System (ADS)

Zou, Hui; Ma, Lei; Xiong, Hui; Zhang, Yunshan; Li, Yong Tao

2018-01-01

A ring laser temperature sensor based on a novel reflective fiber Fabry-Perot (F-P) interferometer air cavity is proposed and experimentally demonstrated. The reflective F-P air cavity, which consists of a segment of glass capillary inserted between two single-mode fibers, is utilized as a sensing element as well as as a filter in the fiber ring cavity. As temperature increases, the reflection spectra of the F-P sensor move towards the longer wavelength, and then cause lasing wavelength shifts. By monitoring the variation of lasing wavelength, we obtain a temperature sensor system with a high temperature sensitivity of 0.249 nm °C-1, a narrow 3 dB bandwidth of 0.1514 nm, and a high signal-to-noise ratio of 52 dB. Moreover, it is convenient to fabricate the sensor head, and the stability is very good, giving it a wide range of applications.

An historical overview of cavity-enhanced methods

NASA Astrophysics Data System (ADS)

Paldus, B. A.; Kachanov, A. A.

2005-10-01

An historical overview of laser-based, spectroscopic methods that employ high-finesse optical resonators is presented. The overview begins with the early work in atomic absorption (1962) and optical cavities (1974) that led to the first mirror reflectivity measurements in 1980. This paper concludes with very recent extensions of cavity-enhanced methods for the study of condensed-phase media and biological systems. Methods described here include cavity ring-down spectroscopy, integrated cavity output spectroscopy, and noise-immune cavity-enhanced optical heterodyne molecular spectroscopy. Given the explosive growth of the field over the past decade, this review does not attempt to present a comprehensive bibliography of all work published in cavity-enhanced spectroscopy, but rather strives to illustrate the rich history, creative diversity, and broad applications potential of these methods.

Coherent Fiber Optic Links

DTIC Science & Technology

1990-12-01

since drift is common to both signal and local oscillator. However because of the Fabry - Perot cavity of the phase -6.9- Electrical delay 5.429077 ns___...Phase modulation gives intensity modulation of the guided light of .13dB max. This is due to formation of a Fabry - Perot cavity between the two fibre/chip...modulation sidebands using an optical spectrum analyser (scanning a Fabry - Perot interferometer), while monitoring the r.f. drive power incident on the

CEBAF Superconducting Cavity RF Drive System

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

Fugitt, Jock; Moore, Thomas

1987-03-01

The CEBAR RF system consists of 418 individual RF amplifier chains. Each superconducting cavity is phase locked to the master drive reference line to within 1 degree, and the cavity field gradient is regulated to within 1 part in 10 by a state-of-the-art RF control module. Precision, continuously adjustable, modulo 360 phase shifters are used to generate the individual phase references, and a compensated RF detector is used for level feedback. The close coupled digital system enhances system accuracy, provides self-calibration, and continuously checks the system for malfunction. Calibration curves, the operating program, and system history are stored in anmore » on board EEPROM. The RF power is generated by a 5Kw, water cooled, permanent magnet focused klystorn. The klystons are clustered in groups of 8 and powered from a common supply. RF power is transmitted to the accelerator sections by semiflexible waveguide.« less

Modulated phases of graphene quantum Hall polariton fluids

PubMed Central

Pellegrino, Francesco M. D.; Giovannetti, Vittorio; MacDonald, Allan H.; Polini, Marco

2016-01-01

There is a growing experimental interest in coupling cavity photons to the cyclotron resonance excitations of electron liquids in high-mobility semiconductor quantum wells or graphene sheets. These media offer unique platforms to carry out fundamental studies of exciton-polariton condensation and cavity quantum electrodynamics in a regime, in which electron–electron interactions are expected to play a pivotal role. Here, focusing on graphene, we present a theoretical study of the impact of electron–electron interactions on a quantum Hall polariton fluid, that is a fluid of magneto-excitons resonantly coupled to cavity photons. We show that electron–electron interactions are responsible for an instability of graphene integer quantum Hall polariton fluids towards a modulated phase. We demonstrate that this phase can be detected by measuring the collective excitation spectra, which is often at a characteristic wave vector of the order of the inverse magnetic length. PMID:27841346

Quantum Synchronization of Two Ensembles of Atoms

NASA Astrophysics Data System (ADS)

Xu, Minghui; Tieri, David; Fine, Effie; Thompson, James; Holland, Murray

2014-05-01

We present a system that exhibits quantum synchronization as a modern analogue of the Huygens experiment which is implemented using state-of-the-art neutral atom lattice clocks of the highest precision. In particular, we study the correlated phase dynamics of two mesoscopic ensembles of atoms through their collective coupling to an optical cavity. We find a dynamical quantum phase transition induced by pump noise and cavity output-coupling. The spectral properties of the superradiant light emitted from the cavity show that at a critical pump rate the system undergoes a transition from the independent behavior of two disparate oscillators to the phase-locking that is the signature of quantum synchronization. Besides being of fundamental importance in nonequilibrium quantum many-body physics, this work could have broad implications for many practical applications of ultrastable lasers and precision measurements. This work was supported by the DARPA QuASAR program, the NSF, and NIST.

Electro-optic Modulation Using a DAST Single-crystal Film in a Fabry-Perot Cavity

NASA Astrophysics Data System (ADS)

Kutty, S. P.

2005-03-01

In this paper, we report a multiple-pass electro-optic modulator using a single- crystal film of 4'-dimethyamino-N-methyl-4-stilbazolium tosylate (DAST) placed inside a Fabry-Perot cavity. The single-crystal film was prepared using the modified shear method. Electro-optic modulation was achieved at 633 nm using field-induced birefringence in the cross polarized geometry including the Fabry-Perot cavity. The modulation due to the electro-optic effect was recorded as a function of phase while the phase was controlled by moving one of the mirrors in the cavity. The observed modulation was high (80 percent) for a low field (0.5V/micron) applied along the charge transfer axis on the film. Similar modulation using the Fabry-Perot cavity with a lower modulation depth was observed involving electroabsorption at 633 nm. Electroabsorption in the DAST film has been recently reported [1]. These are important results considering applications in photonics. [1] ``Electroabsorption in single-crystal film of a second-order optical material,'' R. K. Swamy, S. P. Kutty, J. Titus, S. Khatavkar, and M. Thakur, APL, Vol. 85, 4025, (2004).

Phase shifts in the Fourier spectra of phase gratings and phase grids: an application for one-shot phase-shifting interferometry.

PubMed

Toto-Arellano, Noel-Ivan; Rodriguez-Zurita, Gustavo; Meneses-Fabian, Cruz; Vazquez-Castillo, Jose F

2008-11-10

Among several techniques, phase shifting interferometry can be implemented with a grating used as a beam divider to attain several interference patterns around each diffraction order. Because each pattern has to show a different phase-shift, a suitable shifting technique must be employed. Phase gratings are attractive to perform the former task due to their higher diffraction efficiencies. But as is very well known, the Fourier coefficients of only-phase gratings are integer order Bessel functions of the first kind. The values of these real-valued functions oscillate around zero, so they can adopt negative values, thereby introducing phase shifts of pi at certain diffraction orders. Because this almost trivial fact seems to have been overlooked in the literature regarding its practical implications, in this communication such phase shifts are stressed in the description of interference patterns obtained with grating interferometers. These patterns are obtained by placing two windows in the object plane of a 4f system with a sinusoidal grating/grid in the Fourier plane. It is shown that the corresponding experimental observations of the fringe modulation, as well as the corresponding phase measurements, are all in agreement with the proposed description. A one-shot phase shifting interferometer is finally proposed taking into account these properties after proper incorporation of modulation of polarization.

HOM frequency control of SRF cavity in high current ERLs

NASA Astrophysics Data System (ADS)

Xu, Chen; Ben-Zvi, Ilan

2018-03-01

The acceleration of high-current beam in Superconducting Radio Frequency (SRF) cavities is a challenging but essential for a variety of advanced accelerators. SRF cavities should be carefully designed to minimize the High Order Modes (HOM) power generated in the cavities by the beam current. The reduction of HOM power we demonstrate in a particular case can be quite large. This paper presents a method to systematically control the HOM resonance frequencies in the initial design phase to minimize the HOM power generation. This method is expected to be beneficial for the design of high SRF cavities addressing a variety of Energy Recovery Linac (ERL) applications.

Numerical study of wavelength-swept semiconductor ring lasers: the role of refractive-index nonlinearities in semiconductor optical amplifiers and implications for biomedical imaging applications.

PubMed

Bilenca, A; Yun, S H; Tearney, G J; Bouma, B E

2006-03-15

Recent results have demonstrated unprecedented wavelength-tuning speed and repetition rate performance of semiconductor ring lasers incorporating scanning filters. However, several unique operational characteristics of these lasers have not been adequately explained, and the lack of an accurate model has hindered optimization. We numerically investigated the characteristics of these sources, using a semiconductor optical amplifier (SOA) traveling-wave Langevin model, and found good agreement with experimental measurements. In particular, we explored the role of the SOA refractive-index nonlinearities in determining the intracavity frequency-shift-broadening and the emitted power dependence on scan speed and direction. Our model predicts both continuous-wave and pulse operation and shows a universal relationship between the output power of lasers that have different cavity lengths and the filter peak frequency shift per round trip, therefore revealing the advantage of short cavities for high-speed biomedical imaging.

Magnetization transfer from laser-polarized xenon to protons located in the hydrophobic cavity of the wheat nonspecific lipid transfer protein

PubMed Central

Landon, Céline; Berthault, Patrick; Vovelle, Françoise; Desvaux, Hervé

2001-01-01

Nonspecific lipid transfer protein from wheat is studied by liquid-state NMR in the presence of xenon. The gas–protein interaction is indicated by the dependence of the protein proton chemical shifts on the xenon pressure and formally confirmed by the first observation of magnetization transfer from laser-polarized xenon to the protein protons. Twenty-six heteronuclear nOes have allowed the characterization of four interaction sites inside the wheat ns-LTP cavity. Their locations are in agreement with the variations of the chemical shifts under xenon pressure and with solvation simulations. The richness of the information obtained by the noble gas with a nuclear polarization multiplied by ∼12,000 makes this approach based on dipolar cross-relaxation with laser-polarized xenon promising for probing protein hydrophobic pockets at ambient pressure. PMID:11274467

Enhanced photoelastic modulation in silica phononic crystal cavities

NASA Astrophysics Data System (ADS)

Kim, Ingi; Iwamoto, Satoshi; Arakawa, Yasuhiko

2018-04-01

The enhanced photoelastic modulation in quasi-one-dimensional (1D) phononic crystal (PnC) cavities made of fused silica is experimentally demonstrated. A confined acoustic wave in the cavity can induce a large birefringence through the photoelastic effect and enable larger optical modulation amplitude at the same acoustic power. We observe a phase retardation of ∼26 mrad of light passing through the cavity when the exciting acoustic frequency is tuned to the cavity mode resonance of ∼500 kHz at 2.5 V. In the present experiment, a 16-fold enhancement of retardation in the PnC cavity is demonstrated compared with that in a bar-shaped silica structure. Spatially resolved optical retardation measurement reveals that the large retardation is realized only around the cavity reflecting the localized nature of the acoustic cavity mode. The enhanced interactions between acoustic waves and light can be utilized to improve the performance of acousto-optic devices such as photoelastic modulators.

Dispersive Readout of Adiabatic Phases

NASA Astrophysics Data System (ADS)

Kohler, Sigmund

2017-11-01

We propose a protocol for the measurement of adiabatic phases of periodically driven quantum systems coupled to an open cavity that enables dispersive readout. It turns out that the cavity transmission exhibits peaks at frequencies determined by a resonance condition that involves the dynamical and the geometric phase. Since these phases scale differently with the driving frequency, one can determine them by fitting the peak positions to the theoretically expected behavior. For the derivation of the resonance condition and for a numerical study, we develop a Floquet theory for the dispersive readout of ac driven quantum systems. The feasibility is demonstrated for two test cases that generalize Landau-Zener-Stückelberg-Majorana interference to two-parameter driving.

Controlled waveguide coupling for photon emission from colloidal PbS quantum dot using tunable microcavity made of optical polymer and silicon

NASA Astrophysics Data System (ADS)

Nozaka, Takahiro; Mukai, Kohki

2016-04-01

A tunable microcavity device composed of optical polymer and Si with a colloidal quantum dot (QD) is proposed as a single-photon source for planar optical circuit. Cavity size is controlled by electrostatic micromachine behavior with the air bridge structure to tune timing of photon injection into optical waveguide from QD. Three-dimensional positioning of a QD in the cavity structure is available using a nanohole on Si processed by scanning probe microscope lithography. We fabricated the prototype microcavity with PbS-QD-mixed polymenthyl methacrylate on a SOI (semiconductor-on-insulator) substrate to show the tunability of cavity size as the shift of emission peak wavelength of QD ensemble.

Observation of an optical spring with a beam splitter

NASA Astrophysics Data System (ADS)

Cripe, Jonathan; Danz, Baylee; Lane, Benjamin; Lorio, Mary Catherine; Falcone, Julia; Cole, Garrett D.; Corbitt, Thomas

2018-05-01

We present the experimental observation of an optical spring without the use of an optical cavity. The optical spring is produced by interference at a beamsplitter and, in principle, does not have the damping force associated with optical springs created in detuned cavities. The experiment consists of a Michelson-Sagnac interferometer (with no recycling cavities) with a partially reflective GaAs microresonator as the beamsplitter that produces the optical spring. Our experimental measurements at input powers of up to 360 mW show the shift of the optical spring frequency as a function of power and are in excellent agreement with theoretical predictions. In addition, we show that the optical spring is able to keep the interferometer stable and locked without the use of external feedback.

Micromachined structures for vertical microelectrooptical devices on InP

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

Seassal, C.; Leclercq, J.L.; Letartre, X.

1996-12-31

The authors presented a microstructuring method in order to fabricate tunable vertical resonant cavity optical devices. PL characterizations were performed on a test structure in order to evaluate the effect of the cavity thickness on the peak characteristics. Modeling of the mechanical, electrostatic, and optical behavior of the device, PL simulation were performed, and showed a good agreement with the experiments. This is a first preliminary validation of InP-based MOEMS for further realization of tunable wavelength-selective passive filters, or photodiodes and lasers by incorporating active region within the cavity. Micro-reflectivity measurements with a spatial resolution of 20 {micro}m are underwaymore » in their group, in order to measure directly the resonance shift and spectral linewidth.« less

Design and analysis of photonic crystal micro-cavity based optical sensor platform

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

Goyal, Amit Kumar, E-mail: amitgoyal.ceeri@gmail.com; Dutta, Hemant Sankar, E-mail: hemantdutta97@gmail.com; Pal, Suchandan, E-mail: spal@ceeri.ernet.in

2016-04-13

In this paper, the design of a two-dimensional photonic crystal micro-cavity based integrated-optic sensor platform is proposed. The behaviour of designed cavity is analyzed using two-dimensional Finite Difference Time Domain (FDTD) method. The structure is designed by deliberately inserting some defects in a photonic crystal waveguide structure. Proposed structure shows a quality factor (Q) of about 1e5 and the average sensitivity of 500nm/RIU in the wavelength range of 1450 – 1580 nm. Sensing technique is based on the detection of shift in upper-edge cut-off wavelength for a reference signal strength of –10 dB in accordance with the change in refractive index ofmore » analyte.« less

Continuous-wave supercontinuum laser based on an erbium-doped fiber ring cavity incorporating a highly nonlinear optical fiber.

PubMed

Lee, Ju Han; Takushima, Yuichi; Kikuchi, Kazuro

2005-10-01

We experimentally demonstrate a novel erbium-doped fiber based continuous-wave (cw) supercontinuum laser. The laser has a simple ring-cavity structure incorporating an erbium-doped fiber and a highly nonlinear dispersion-shifted fiber (HNL-DSF). Differently from previously demonstrated cw supercontinuum sources based on single propagation of a strong Raman pump laser beam through a highly nonlinear fiber, erbium gain inside the cavity generates a seed light oscillation, and the oscillated light subsequently evolves into a supercontinuum by nonlinear effects such as modulation instability and stimulated Raman scattering in the HNL-DSF. High quality of the depolarized supercontinuum laser output with a spectral bandwidth larger than 250 nm is readily achieved.

Parallel-quadrature phase-shifting digital holographic microscopy using polarization beam splitter

PubMed Central

Das, Bhargab; Yelleswarapu, Chandra S; Rao, DVGLN

2012-01-01

We present a digital holography microscopy technique based on parallel-quadrature phase-shifting method. Two π/2 phase-shifted holograms are recorded simultaneously using polarization phase-shifting principle, slightly off-axis recording geometry, and two identical CCD sensors. The parallel phase-shifting is realized by combining circularly polarized object beam with a 45° degree polarized reference beam through a polarizing beam splitter. DC term is eliminated by subtracting the two holograms from each other and the object information is reconstructed after selecting the frequency spectrum of the real image. Both amplitude and phase object reconstruction results are presented. Simultaneous recording eliminates phase errors caused by mechanical vibrations and air turbulences. The slightly off-axis recording geometry with phase-shifting allows a much larger dimension of the spatial filter for reconstruction of the object information. This leads to better reconstruction capability than traditional off-axis holography. PMID:23109732

On the wall perturbation correction for a parallel-plate NACP-02 chamber in clinical electron beams.

PubMed

Zink, K; Wulff, J

2011-02-01

In recent years, several Monte Carlo studies have been published concerning the perturbation corrections of a parallel-plate chamber in clinical electron beams. In these studies, a strong depth dependence of the relevant correction factors (p(wall) and P(cav)) for depth beyond the reference depth is recognized and it has been shown that the variation with depth is sensitive to the choice of the chamber's effective point of measurement. Recommendations concerning the positioning of parallel-plate ionization chambers in clinical electron beams are not the same for all current dosimetry protocols. The IAEA TRS-398 as well as the IPEM protocol and the German protocol DIN 6800-2 interpret the depth of measurement within the phantom as the water equivalent depth, i.e., the nonwater equivalence of the entrance window has to be accounted for by shifting the chamber by an amount deltaz. This positioning should ensure that the primary electrons traveling from the surface of the water phantom through the entrance window to the chamber's reference point sustain the same energy loss as the primary electrons in the undisturbed phantom. The objective of the present study is the determination of the shift deltaz for a NACP-02 chamber and the calculation of the resulting wall perturbation correction as a function of depth. Moreover, the contributions of the different chamber walls to the wall perturbation correction are identified. The dose and fluence within the NACP-02 chamber and a wall-less air cavity is calculated using the Monte Carlo code EGSnrc in a water phantom at different depths for different clinical electron beams. In order to determine the necessary shift to account for the nonwater equivalence of the entrance window, the chamber is shifted in steps deltaz around the depth of measurement. The optimal shift deltaz is determined from a comparison of the spectral fluence within the chamber and the bare cavity. The wall perturbation correction is calculated as the ratio between doses for the complete chamber and a wall-less air cavity. The high energy part of the fluence spectra within the chamber strongly varies even with small chamber shifts, allowing the determination of deltaz within micrometers. For the NACP-02 chamber a shift deltaz = -0.058 cm results. This value is independent of the energy of the primary electrons as well as of the depth within the phantom and it is in good agreement with the value recommended in the German dosimetry protocol. Applying this shift, the calculated wall perturbation correction as a function of depth is varying less than 1% from zero up to the half value depth R50 for electron energies in the range of 6-21 MeV. The remaining depth dependence can mainly be attributed to the scatter properties of the entrance window. When neglecting the nonwater equivalence of the entrance window, the variation of p(wall) with depth is up to 10% and more, especially for low electron energies. The variation of the wall perturbation correction for the NACP-02 chamber in clinical electron beams strongly depends on the positioning of the chamber. Applying a shift deltaz = -0.058 cm toward the focus ensures that the primary electron spectrum within the chamber bears the largest resemblance to the fluence of a wall-less cavity. Hence, the influence of the chamber walls on the perturbation correction can be separated out and the residual variation of p(wall) with depth is minimized.

Synchronization of natural convection in thermostatically-controlled adjacent cavities

NASA Astrophysics Data System (ADS)

Chavez-Martinez, Rafael; Sanchez-Lopez, Mario; Solorio-Ordaz, Francisco Javier; Sen, Mihir

2017-11-01

Synchronization is a phenomenon observed in complex dynamical systems. It was first noticed by Huygens in the 17th century, and since then has been observed in systems of different types such as mechanical, biological and social. In thermal systems, numerical and analytical studies have found that two or more similar heat sources, with independent thermostatic temperature control and communicating with each other through a common interface, can have temperature oscillations. In the present study, laboratory experiments were carried out to study the thermal synchronization in two cuboid rooms separated by a common wall. Computer-based thermostats independently control the temperature of each cavity. The experiments show the effect of the ambient temperature and the initial condition in the cavities on the phase difference Δϕ . The results demonstrate in-phase and out-of-phase synchronization. An increase of the temperature difference between the cavity and the ambient, ΔT , increases Δϕ . When ΔT <2° C, Δϕ oscillates around zero. Δϕ is negative independently of the initial condition. The results of these experiments will be useful in the desing of heating in full-scale buildings. This work is supported by DGAPA-UNAM Grant PAPIIT-IN114216.

A Multi-Phase Based Fluid-Structure-Microfluidic interaction sensor for Aerodynamic Shear Stress

NASA Astrophysics Data System (ADS)

Hughes, Christopher; Dutta, Diganta; Bashirzadeh, Yashar; Ahmed, Kareem; Qian, Shizhi

2014-11-01

A novel innovative microfluidic shear stress sensor is developed for measuring shear stress through multi-phase fluid-structure-microfluidic interaction. The device is composed of a microfluidic cavity filled with an electrolyte liquid. Inside the cavity, two electrodes make electrochemical velocimetry measurements of the induced convection. The cavity is sealed with a flexible superhydrophobic membrane. The membrane will dynamically stretch and flex as a result of direct shear cross-flow interaction with the seal structure, forming instability wave modes and inducing fluid motion within the microfluidic cavity. The shear stress on the membrane is measured by sensing the induced convection generated by membrane deflections. The advantages of the sensor over current MEMS based shear stress sensor technology are: a simplified design with no moving parts, optimum relationship between size and sensitivity, no gaps such as those created by micromachining sensors in MEMS processes. We present the findings of a feasibility study of the proposed sensor including wind-tunnel tests, microPIV measurements, electrochemical velocimetry, and simulation data results. The study investigates the sensor in the supersonic and subsonic flow regimes. Supported by a NASA SBIR phase 1 contract.

Semiconductor Nonlinear Waveguide Devices and Integrated-Mirror Etalons

NASA Astrophysics Data System (ADS)

Chuang, Chih-Li.

This dissertation investigates different III-V semiconductor devices for applications in nonlinear photonics. These include passive and active nonlinear directional couplers, current-controlled optical phase shifter, and integrated -mirror etalons. A novel method to find the propagation constants of an optical waveguide is introduced. The same method is applied, with minor modifications, to find the coupling length of a directional coupler. The method presented provides a tool for the design of optical waveguide devices. The design, fabrication, and performance of a nonlinear directional coupler are presented. This device uses light intensity to control the direction of light coming out. This is achieved through photo-generated-carriers mechanism in the picosecond regime and through the optical Stark effect in the femtosecond regime. A two-transverse -dimensions beam-propagation computation is used to model the switching behavior in the nonlinear directional coupler. It is found that, by considering the pulse degradation effect, the computation agrees well with experiments. The possibility of operating a nonlinear directional coupler with gain is investigated. It is concluded that by injecting current into the nonlinear directional coupler does not provide the advantages hoped for and the modelling using 2-D beam -propagation methods verifies that. Using current injection to change the refractive index of a waveguide, an optical phase shifter is constructed. This device has the merit of delivering large phase shift with almost no intensity modulation. A phase shift as large as 3pi is produced in a waveguide 400 μm in length. Finally, a new structure, grown by the molecular beam epitaxy machine, is described. The structure consists of two quarter-wave stacks and a spacer layer to form an integrated-mirror etalon. The theory, design principles, spectral analyses are discussed with design examples to clarify the ideas. Emphasis is given to the vertical-cavity surface-emitting laser constructed from this structure. Here we demonstrated the cw operation of the VCSEL at room temperature.

Measurement of a free spectral range of a Fabry-Perot cavity using frequency modulation and null method under off-resonance conditions

NASA Astrophysics Data System (ADS)

Aketagawa, Masato; Kimura, Shohei; Yashiki, Takuya; Iwata, Hiroshi; Banh, Tuan Quoc; Hirata, Kenji

2011-02-01

In this paper, we discuss a method to measure the free spectral range (FSR) of a Fabry-Perot cavity (FP-cavity) using frequency modulation with one electric optical modulator (EOM) and the null method. A laser beam modulated by the EOM, to which a sine wave signal is supplied from a radio frequency (RF) oscillator, is incident on the FP-cavity. The transmitted or reflected light from the FP-cavity is observed and converted to an RF signal by a high-speed photodetector, and the RF signal is synchronously demodulated with a lock-in amplifier by referring to a cosine wave signal from the oscillator. We theoretically and experimentally demonstrate that the lock-in amplifier signal for the transmitted or reflected light becomes null with a steep slope when the modulation frequency is equal to the FSR under the condition that the carrier frequency of the laser is slightly detuned from the resonance of the FP-cavity. To reduce the measurement uncertainty for the FSR, we also discuss a selection method for laser power, a modulation index and the detuning shift of the carrier frequency, respectively.

Tunneling and traversal of ultracold three-level atoms through vacuum-induced potentials

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

Badshah, Fazal; Irfan, Muhammad; Qamar, Shahid

2011-09-15

The passage of ultracold three-level atoms through the potential induced by the vacuum cavity mode is discussed using cascade atomic configuration. We study the tunneling or traversal time of the ultracold atoms via a bimodal high-Q cavity. It is found that the phase time, which may be considered as a measure for the time required to traverse the cavity, exhibits superclassical and subclassical behaviors. Further, the dark states and interference effects in cascade atomic configuration may influence the passage time of the atom through the cavity.

Design and performance of the LCLS cavity BPM system.

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

Lill, R.; Norum, E.; Morrison, L.

2008-01-01

In this paper we present the design of the beam position monitor (BPM) system for the LCLS undulator, which features a high-resolution X-band cavity BPM. Each BPM has a TM{sub 010} monopole reference cavity and a TM{sub 110} dipole cavity designed to operate at a center frequency of 11.384 GHz. The signal processing electronics features a low- noise single-stage three-channel heterodyne receiver that has selectable gain and a phase locking local oscillator. We will discuss the system specifications, design, and prototype test results.

Design and Performance of the LCLS Cavity BPM System

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

Lill, R.M.; Morrison, L.H.; Norum, W.E.

2008-01-23

In this paper we present the design of the beam position monitor (BPM) system for the LCLS undulator, which features a high-resolution X-band cavity BPM. Each BPM has a TM{sub 010} monopole reference cavity and a TM{sub 110} dipole cavity designed to operate at a center frequency of 11.384 GHz. The signal processing electronics features a low noise single-stage three-channel heterodyne receiver that has selectable gain and a phase locking local oscillator. We will discuss the system specifications, design, and prototype test results.

Silicon RFIC Techniques for Reconfigurable Military Applications

DTIC Science & Technology

2008-12-01

21 3.2.1 Motivation ...2008-295 21 3.2 Distributed Cascode LNAs at 20 GHz 3.2.1 Motivation Millimetrewave integrated circuits are traditionally implemented using...ZRef=50. Ohm Phase=-45. PhaseShiftSML PS4 ZRef=50. Ohm Phase=-22.5 PhaseShiftSML PS7 ZRef=50. Ohm Phase=-180 PhaseShiftSML PS8 ZRef=50. Ohm Phase=-180

Ultra narrow flat-top filter based on multiple equivalent phase shifts

NASA Astrophysics Data System (ADS)

Wang, Fei; Zou, Xihua; Yin, Zuowei; Chen, Xiangfei; Shen, Haisong

2008-11-01

Instead of real phase shifts, equivalent phase shifts (EPS) are adopted to construct ultra narrow phase-shifted band-pass filer in sampled Bragg gratings (SBG). Two optimized distributions of multiple equivalent phase shifts, using 2 and 5 EPSs respectively, are given in this paper to realize flat-top and ripple-free transmission characteristics simultaneously. Also two demonstrations with 5 EPSs both on hydrogen-loaded and photosensitive fibers are presented and their spectrums are examined by an optical vector analyzer (OVA). Given only ordinary phase mask and sub-micrometer precision control, ultra-narrowband flat-top filters with expected performance can be achieved flexibly and cost-effectively.

Dark goggles and bright light improve circadian rhythm adaptation to night-shift work.

PubMed

Eastman, C I; Stewart, K T; Mahoney, M P; Liu, L; Fogg, L F

1994-09-01

We compared the contributions of bright light during the night shift and dark goggles during daylight for phase shifting the circadian rhythm of temperature to realign with a 12-hour shift of sleep. After 10 baseline days there were 8 night-work/day-sleep days. Temperature was continuously recorded from 50 subjects. There were four groups in a 2 x 2 design: light (bright, dim), goggles (yes, no). Subjects were exposed to bright light (about 5,000 lux) for 6 hours on the first 2 night shifts. Dim light was < 500 lux. Both bright light and goggles were significant factors for producing circadian rhythm phase shifts. The combination of bright light plus goggles was the most effective, whereas the combination of dim light and no goggles was the least effective. The temperature rhythm either phase advanced or phase delayed when it aligned with daytime sleep. However, when subjects did not have goggles only phase advances occurred. Goggles were necessary for producing phase delays. The most likely explanation is that daylight during the travel-home window after a night shift inhibits phase-delay shifts, and goggles can prevent this inhibition. Larger temperature-rhythm phase shifts were associated with better subjective daytime sleep, less subjective fatigue and better mood.

Contributory role of the tongue and mandible in modulating the in-mouth air cavity at rest.

PubMed

Bourdiol, Pierre; Mishellany-Dutour, Anne; Peyron, Marie-Agnes; Woda, Alain

2013-12-01

The tongue-to-palate distance influences the volume of the in-mouth air cavity (IMAC), thus conditioning the entry of aromatic compounds to the olfactory mucosa site. This study was set out to record the IMAC volume by measuring tongue-to-palate distance at rest. Twelve young adults in good general health were tested--lips contacting, with at-rest posture of the tongue and jaw during a silent reading task. Observations in this study were limited to pre- and post-swallowing sequences. The tongue-to-palate distance was measured using three electromagnetic sensors placed on the tongue upper surface. IMAC volume was evaluated from a geometrical model, taking into account the tongue-to-palate distance, the IMAC transversal distance measured from dental casts and historic data giving the anterior-posterior distance of the oral cavity. (1) In the at-rest posture, the tongue-to-palate distance was significantly greater at the posterior sensor level. (2) A vertical shift in tongue posture at rest frequently appeared following deglutition. The upward shifts were of larger amplitude and more frequent than the downward shifts. (3) Evaluation of the IMAC volume gave an approximate value of 12 ml at rest. (4) The chin sensor at rest was 2.8 ± 0.8 mm below its position when in occlusion. The tongue and mandible contribute to shaping the IMAC volume. These and other results suggest that deglutition changes tongue-to-palate distance and influences aroma release during mastication/deglutition acts through modulation of the IMAC volume.

Nonphotic phase shifting in female Syrian hamsters: interactions with the estrous cycle.

PubMed

Young Janik, L; Janik, Daniel

2003-08-01

Nonphotic phase shifting of circadian rhythms was examined in female Syrian hamsters. Animals were stimulated at zeitgeber time 4.5 by either placing them in a novel running wheel or by transferring them to a clean home cage. Placement in a clean home cage was more effective than novel wheel treatment in stimulating large (> 1.5 h) phase shifts. Peak phase shifts (ca. 3.5 h) and the percentage of females showing large phase shifts were comparable to those found in male hamsters stimulated with novel wheels. The amount of activity induced by nonphotic stimulation and the amount of phase shifting varied slightly with respect to the 4-day estrous cycle. Animals tended to run less and shift less on the day of estrus. Nonphotic stimulation on proestrus often resulted in a 1-day delay of the estrous cycle reflected in animals' postovulatory vaginal discharge and the expression of sexual receptivity (lordosis). This delay of the estrous cycle was associated with large phase advances and high activity. These results extend the generality of nonphotic phase shifting to females for the first time and raise the possibility that resetting of circadian rhythms can induce changes in the estrous cycle.

Hyperpolarizability and Operational Magic Wavelength in an Optical Lattice Clock

NASA Astrophysics Data System (ADS)

Brown, R. C.; Phillips, N. B.; Beloy, K.; McGrew, W. F.; Schioppo, M.; Fasano, R. J.; Milani, G.; Zhang, X.; Hinkley, N.; Leopardi, H.; Yoon, T. H.; Nicolodi, D.; Fortier, T. M.; Ludlow, A. D.

2017-12-01

Optical clocks benefit from tight atomic confinement enabling extended interrogation times as well as Doppler- and recoil-free operation. However, these benefits come at the cost of frequency shifts that, if not properly controlled, may degrade clock accuracy. Numerous theoretical studies have predicted optical lattice clock frequency shifts that scale nonlinearly with trap depth. To experimentally observe and constrain these shifts in an 171Yb optical lattice clock, we construct a lattice enhancement cavity that exaggerates the light shifts. We observe an atomic temperature that is proportional to the optical trap depth, fundamentally altering the scaling of trap-induced light shifts and simplifying their parametrization. We identify an "operational" magic wavelength where frequency shifts are insensitive to changes in trap depth. These measurements and scaling analysis constitute an essential systematic characterization for clock operation at the 10-18 level and beyond.

Experience with novel technologies for direct measurement of atmospheric NO2

NASA Astrophysics Data System (ADS)

Hueglin, Christoph; Hundt, Morten; Mueller, Michael; Schwarzenbach, Beat; Tuzson, Bela; Emmenegger, Lukas

2017-04-01

Nitrogen dioxide (NO2) is an air pollutant that has a large impact on human health and ecosystems, and it plays a key role in the formation of ozone and secondary particulate matter. Consequently, legal limit values for NO2 are set in the EU and elsewhere, and atmospheric observation networks typically include NO2 in their measurement programmes. Atmospheric NO2 is principally measured by chemiluminescence detection, an indirect measurement technique that requires conversion of NO2 into nitrogen monoxide (NO) and finally calculation of NO2 from the difference between total nitrogen oxides (NOx) and NO. Consequently, NO2 measurements with the chemiluminescence method have a relatively high measurement uncertainty and can be biased depending on the selectivity of the applied NO2 conversion method. In the past years, technologies for direct and selective measurement of NO2 have become available, e.g. cavity attenuated phase shift spectroscopy (CAPS), cavity enhanced laser absorption spectroscopy and quantum cascade laser absorption spectrometry (QCLAS). These technologies offer clear advantages over the indirect chemiluminescence method. We tested the above mentioned direct measurement techniques for NO2 over extended time periods at atmospheric measurement stations and report on our experience including comparisons with co-located chemiluminescence instruments equipped with molybdenum as well as photolytic NO2 converters. A still open issue related to the direct measurement of NO2 is instrument calibration. Accurate and traceable reference standards and NO2 calibration gases are needed. We present results from the application of different calibration strategies based on the use of static NO2 calibration gases as well as dynamic NO2 calibration gases produced by permeation and by gas-phase titration (GPT).

Molecular laser stabilization for LISA

NASA Astrophysics Data System (ADS)

Halloin, Hubert; Acef, Ouali; Argence, Berengere; Jeannin, Olivier; Prat, Pierre; de Vismes, Eden; Plagnol, Eric; Brillet, Alain; Mondin, Linda; Berthon, Jacques; Turazza, Oscar

2017-11-01

The expected performance of LISA relies on two main technical challenges: the ability for the spacecrafts to precisely follow the free-flying masses and the outstanding precision of the phase shift measurement. This latter constraint requires frequency stabilized lasers and efficient numerical algorithms to account for the redundant, delayed noise propagation, thus cancelling laser phase noise by many orders of magnitude (TDI methods). Recently involved in the technical developments for LISA, the goal of our team at APC (France) is to contribute on these two subjects: frequency reference for laser stabilization and benchtop simulation of the interferometer. In the present design of LISA, two stages of laser stabilization are used (not accounting for the "post-processed" TDI algorithm): laser pre-stabilization on a frequency reference and lock on the ultra stable distance between spacecrafts (arm-locking). While the foreseen (and deeply studied) laser reference consists of a Fabry-Perot cavity, other techniques may be suitable for LISA or future metrology missions. In particular, locking to a molecular reference (namely iodine in the case of the LISA Nd:YAG laser) is an interesting alternative. It offers the required performance with very good long-term stability (absolute frequency reference) though the reference can be slightly tuned to account for arm-locking. This technique is currently being investigated by our team and optimized for LISA (compactness, vacuum compatibility, ease of use and initialization, etc.). A collaboration with a French laboratory (the SYRTE) had been started aiming to study a second improved technique consisting in inserting the iodine cell in a Fabry-Perot cavity. Ongoing results and prospects to increase the performance of the system are presented in the present article.

Dynamics of a coherently driven micromaser by the Monte Carlo wavefunction approach

NASA Astrophysics Data System (ADS)

Bonacina, L.; Casagrande, F.; Lulli, A.

2000-08-01

Using a Monte Carlo wavefunction approach we investigate the dynamics of a micromaser driven by a resonant coherent field. At steady state, for increasing interaction times, the system exhibits driven Rabi oscillations, followed by collapse as the range of micromaser trapping states is approached. The system operates in regimes ranging from a strong to a weak amplifier. In the strong-amplifier regime the cavity mode shows a preferred phase and can exhibit quadrature squeezing and sub-Poissonian photon statistics. In the weak-amplifier regime the cavity mode has no preferred phase, is super-Poissonian and is influenced by trapping effects; no revival of Rabi oscillations occurs. The main predictions can be compared with experimental measurements on the populations of atoms leaving the cavity.

Coherent emission from integrated Talbot-cavity quantum cascade lasers.

PubMed

Meng, Bo; Qiang, Bo; Rodriguez, Etienne; Hu, Xiao Nan; Liang, Guozhen; Wang, Qi Jie

2017-02-20

We report experimental realization of phase-locked quantum cascade laser (QCL) array using a monolithically integrated Talbot cavity. An array with six laser elements at a wavelength of ~4.8 μm shows a maximum peak power of ~4 W which is more than 5 times higher than that of a single ridge laser element and a slope efficiency of 1 W/A at room temperature. Operation of in-phase coherent supermode has been achieved over the whole dynamic range of the Talbot-cavity QCL. The structure was analysed using a straightforward theoretical model, showing quantitatively good agreement with the experimental results. The reduced thermal resistance makes the structure an attractive approach to achieve high beam quality continuous wave QCLs.

Compact, thermal-noise-limited reference cavity for ultra-low-noise microwave generation.

PubMed

Davila-Rodriguez, J; Baynes, F N; Ludlow, A D; Fortier, T M; Leopardi, H; Diddams, S A; Quinlan, F

2017-04-01

We demonstrate an easy-to-manufacture 25-mm-long ultra-stable optical reference cavity for transportable photonic microwave generation systems. Employing a rigid holding geometry that is first-order insensitive to the squeezing force and a cavity geometry that improves the thermal noise limit at room temperature, we observe a laser phase noise that is nearly thermal noise limited for three frequency decades (1 Hz to 1 kHz offset) and supports 10 GHz generation with phase noise near -100  dBc/Hz at 1 Hz offset and <-173  dBc/Hz for all offsets >600  Hz. The fractional frequency stability reaches 2×10^-15 at 0.1 s of averaging.

Quantum phases of spinful Fermi gases in optical cavities

NASA Astrophysics Data System (ADS)

Colella, E.; Citro, R.; Barsanti, M.; Rossini, D.; Chiofalo, M.-L.

2018-04-01

We explore the quantum phases emerging from the interplay between spin and motional degrees of freedom of a one-dimensional quantum fluid of spinful fermionic atoms, effectively interacting via a photon-mediating mechanism with tunable sign and strength g , as it can be realized in present-day experiments with optical cavities. We find the emergence, in the very same system, of spin- and atomic-density wave ordering, accompanied by the occurrence of superfluidity for g >0 , while cavity photons are seen to drive strong correlations at all g values, with fermionic character for g >0 , and bosonic character for g <0 . Due to the long-range nature of interactions, to infer these results we combine mean-field and exact-diagonalization methods supported by bosonization analysis.

Femto-second synchronisation with a waveguide interferometer

NASA Astrophysics Data System (ADS)

Dexter, A. C.; Smith, S. J.; Woolley, B. J.; Grudiev, A.

2018-03-01

CERN's compact linear collider CLIC requires crab cavities on opposing linacs to rotate bunches of particles into alignment at the interaction point (IP). These cavities are located approximately 25 metres either side of the IP. The luminosity target requires synchronisation of their RF phases to better than 5 fs r.m.s. This is to be achieved by powering both cavities from one high power RF source, splitting the power and delivering it along two waveguide paths that are controlled to be identical in length to within a micrometre. The waveguide will be operated as an interferometer. A high power phase shifter for adjusting path lengths has been successfully developed and operated in an interferometer. The synchronisation target has been achieved in a low power prototype system.

Long-wavelength VCSELs: Power-efficient answer

NASA Astrophysics Data System (ADS)

Kapon, Eli; Sirbu, Alexei

2009-01-01

The commercialization of long-wavelength vertical-cavity surface-emitting lasers (VCSELs) is gaining new momentum as the telecoms market shifts from long-haul applications to local and access networks. These small, power-efficient devices offer several advantages over traditional edge-emitters.

Secondary Organic Aerosol Formation from Glyoxal: photochemical versus dark uptake and reversible versus irreversible SOA formation

NASA Astrophysics Data System (ADS)

Waxman, E.; Slowik, J. G.; Kampf, C. J.; Timkovsky, J.; Noziere, B.; Praplan, A. P.; Pfaffenberger, L.; Holzinger, R.; Hoffmann, T.; Dommen, J.; Prevot, A. S.; Baltensperger, U.; Volkamer, R.

2011-12-01

Glyoxal forms secondary organic aerosol (SOA) by partitioning to the aerosol aqueous phase according to Henry's law. The subsequent processing by heterogeneous and multiphase reactions shifts the partitioning towards aerosols. Currently it is not well understood whether these reactions result in reversible or irreversible SOA formation, and what parameters influence the rate limiting step of multiphase processing. We conducted a series of simulation chamber experiments at PSI in April and May 2011 to investigate processing under dark conditions, UV and/or visible light irradiated conditions, and in the presence and absence of OH radicals. Experiments used ammonium sulfate or ammonium sulfate/fulvic acid mixtures as seed aerosols, and were conducted between 50% and 85% relative humidity at approximately constant RH over the course of any given experiment. Glyoxal was produced photochemically from acetylene, using HONO photolysis as the OH radical source. Gas-phase glyoxal was measured by the CU LED-Cavity Enhanced-DOAS. The Thermal-Desorption Proton-Transfer-Reaction Mass Spectrometer (TD-PTR-MS) and Ion Chromatography Mass Spectrometer (IC-MS) monitored both gas and aerosol-phase organic reaction products. Particle composition was monitored by High-Resolution Time-of-Flight Aerosol Mass Spectrometry (HR-ToF-AMS), and HPLC-ESI MS/MS and LC-MS analysis of filter samples.

Secondary Organic Aerosol Formation from Glyoxal: photochemical versus dark uptake and reversible versus irreversible SOA formation

NASA Astrophysics Data System (ADS)

Waxman, E.; Slowik, J.; Kampf, C.; Timkovsky, J.; Noziere, B.; Praplan, A.; Pffafenberger, L.; Holzinger, R.; Hoffmann, T.; Dommen, J.; Prevot, A.; Baltensperger, U.; Volkamer, R.

2012-04-01

Glyoxal forms secondary organic aerosol (SOA) by partitioning to the aerosol aqueous phase according to Henry's law. The subsequent processing by heterogeneous and multiphase reactions shifts the partitioning towards aerosols. Currently it is not well understood whether these reactions result in reversible or irreversible SOA formation, and what parameters influence the rate limiting step of multiphase processing. We conducted a series of simulation chamber experiments at PSI in April and May 2011 to investigate processing under dark conditions, UV and/or visible light irradiated conditions, and in the presence and absence of OH radicals. Experiments used ammonium sulfate or ammonium sulfate/fulvic acid mixtures as seed aerosols, and were conducted between 50% and 85% relative humidity at approximately constant RH over the course of any given experiment. Glyoxal was produced photochemically from acetylene, using HONO photolysis as the OH radical source. Gas-phase glyoxal was measured by the CU LED-Cavity Enhanced-DOAS. The Thermal-Desorption Proton-Transfer-Reaction Mass Spectrometer (TD-PTR-MS) and Ion Chromatography Mass Spectrometer (IC-MS) monitored both gas and aerosol-phase organic reaction products. Particle composition was monitored by High-Resolution Time-of-Flight Aerosol Mass Spectrometry (HR-ToF-AMS), and HPLC-ESI MS/MS and LC-MS analysis of filter samples.

Alternative stable states and phase shifts in coral reefs under anthropogenic stress.

PubMed

Fung, Tak; Seymour, Robert M; Johnson, Craig R

2011-04-01

Ecosystems with alternative stable states (ASS) may shift discontinuously from one stable state to another as environmental parameters cross a threshold. Reversal can then be difficult due to hysteresis effects. This contrasts with continuous state changes in response to changing environmental parameters, which are less difficult to reverse. Worldwide degradation of coral reefs, involving "phase shifts" from coral to algal dominance, highlights the pressing need to determine the likelihood of discontinuous phase shifts in coral reefs, in contrast to continuous shifts with no ASS. However, there is little evidence either for or against the existence of ASS for coral reefs. We use dynamic models to investigate the likelihood of continuous and discontinuous phase shifts in coral reefs subject to sustained environmental perturbation by fishing, nutrification, and sedimentation. Our modeling results suggest that coral reefs with or without anthropogenic stress can exhibit ASS, such that discontinuous phase shifts can occur. We also find evidence to support the view that high macroalgal growth rates and low grazing rates on macroalgae favor ASS in coral reefs. Further, our results suggest that the three stressors studied, either alone or in combination, can increase the likelihood of both continuous and discontinuous phase shifts by altering the competitive balance between corals and algae. However, in contrast to continuous phase shifts, we find that discontinuous shifts occur only in model coral reefs with parameter values near the extremes of their empirically determined ranges. This suggests that continuous shifts are more likely than discontinuous shifts in coral reefs. Our results also suggest that, for ecosystems in general, tackling multiple human stressors simultaneously maximizes resilience to phase shifts, ASS, and hysteresis, leading to improvements in ecosystem health and functioning.

EUV phase-shifting masks and aberration monitors

NASA Astrophysics Data System (ADS)

Deng, Yunfei; Neureuther, Andrew R.

2002-07-01

Rigorous electromagnetic simulation with TEMPEST is used to examine the use of phase-shifting masks in EUV lithography. The effects of oblique incident illumination and mask patterning by ion-mixing of multilayers are analyzed. Oblique incident illumination causes streamers at absorber edges and causes position shifting in aerial images. The diffraction waves between ion-mixed and pristine multilayers are observed. The phase-shifting caused by stepped substrates is simulated and images show that it succeeds in creation of phase-shifting effects. The diffraction process at the phase boundary is also analyzed. As an example of EUV phase-shifting masks, a coma pattern and probe based aberration monitor is simulated and aerial images are formed under different levels of coma aberration. The probe signal rises quickly as coma increases as designed.

On temporal dynamics of Sn2P2S6 oscillation in semi-linear cavity.

PubMed

Arciszewski, D; Shumelyuk, A; Odoulov, S

2013-06-01

Experimental measurements and calculations revealed an unusual type of oscillation dynamics of Sn(2)P(2)S(6) in the semi-linear cavity. It consists of a pronounced saw-tooth modulation of oscillation intensity--although it is not 100% in contrast--with the cw component being shifted in frequency with respect to the pump wave. This effect is attributed to the hybrid mode of two semi-linear oscillation geometries, one with a single pump wave and the other with two counterpropagating pump waves.

Wavelength shifting of intra-cavity photons: Adiabatic wavelength tuning in rapidly wavelength-swept lasers

PubMed Central

Jirauschek, Christian; Huber, Robert

2015-01-01

We analyze the physics behind the newest generation of rapidly wavelength tunable sources for optical coherence tomography (OCT), retaining a single longitudinal cavity mode during operation without repeated build up of lasing. In this context, we theoretically investigate the currently existing concepts of rapidly wavelength-swept lasers based on tuning of the cavity length or refractive index, leading to an altered optical path length inside the resonator. Specifically, we consider vertical-cavity surface-emitting lasers (VCSELs) with microelectromechanical system (MEMS) mirrors as well as Fourier domain mode-locked (FDML) and Vernier-tuned distributed Bragg reflector (VT-DBR) lasers. Based on heuristic arguments and exact analytical solutions of Maxwell’s equations for a fundamental laser resonator model, we show that adiabatic wavelength tuning is achieved, i.e., hopping between cavity modes associated with a repeated build up of lasing is avoided, and the photon number is conserved. As a consequence, no fundamental limit exists for the wavelength tuning speed, in principle enabling wide-range wavelength sweeps at arbitrary tuning speeds with narrow instantaneous linewidth. PMID:26203373

Measurement Of Multiphase Flow Water Fraction And Water-cut

NASA Astrophysics Data System (ADS)

Xie, Cheng-gang

2007-06-01

This paper describes a microwave transmission multiphase flow water-cut meter that measures the amplitude attenuation and phase shift across a pipe diameter at multiple frequencies using cavity-backed antennas. The multiphase flow mixture permittivity and conductivity are derived from a unified microwave transmission model for both water- and oil-continuous flows over a wide water-conductivity range; this is far beyond the capability of microwave-resonance-based sensors currently on the market. The water fraction and water cut are derived from a three-component gas-oil-water mixing model using the mixture permittivity or the mixture conductivity and an independently measured mixture density. Water salinity variations caused, for example, by changing formation water or formation/injection water breakthrough can be detected and corrected using an online water-conductivity tracking technique based on the interpretation of the mixture permittivity and conductivity, simultaneously measured by a single-modality microwave sensor.

An extrinsic fiber Fabry-Perot interferometer for dynamic displacement measurement

NASA Astrophysics Data System (ADS)

Pullteap, S.; Seat, H. C.

2015-03-01

A versatile fiber interferometer was proposed for high precision measurement. The sensor exploited a double-cavity within the unique sensing arm of an extrinsic-type fiber Fabry-Perot interferometer to produce the quadrature phase-shifted interference fringes. Interference signal processing was carried out using a modified zero-crossing (fringe) counting technique to demodulate two sets of fringes. The fiber interferometer has been successfully employed for dynamic displacement measurement under different displacement profiles over a range of 0.7 μm to 140 μm. A dedicated computer incorporating the demodulation algorithm was next used to interpret these detected data as well as plot the displacement information with a resolution of λ/64. A commercial displacement sensor was employed for comparison purposes with the experimental data obtained from the fiber interferometer as well as to gauge its performance, resulting in the maximum error of 2.8% over the entire displacement range studied.

Structure-relaxation mechanism for the response of T4 lysozyme cavity mutants to hydrostatic pressure

PubMed Central

Lerch, Michael T.; López, Carlos J.; Yang, Zhongyu; Kreitman, Margaux J.; Horwitz, Joseph; Hubbell, Wayne L.

2015-01-01

Application of hydrostatic pressure shifts protein conformational equilibria in a direction to reduce the volume of the system. A current view is that the volume reduction is dominated by elimination of voids or cavities in the protein interior via cavity hydration, although an alternative mechanism wherein cavities are filled with protein side chains resulting from a structure relaxation has been suggested [López CJ, Yang Z, Altenbach C, Hubbell WL (2013) Proc Natl Acad Sci USA 110(46):E4306–E4315]. In the present study, mechanisms for elimination of cavities under high pressure are investigated in the L99A cavity mutant of T4 lysozyme and derivatives thereof using site-directed spin labeling, pressure-resolved double electron–electron resonance, and high-pressure circular dichroism spectroscopy. In the L99A mutant, the ground state is in equilibrium with an excited state of only ∼3% of the population in which the cavity is filled by a protein side chain [Bouvignies et al. (2011) Nature 477(7362):111–114]. The results of the present study show that in L99A the native ground state is the dominant conformation to pressures of 3 kbar, with cavity hydration apparently taking place in the range of 2–3 kbar. However, in the presence of additional mutations that lower the free energy of the excited state, pressure strongly populates the excited state, thereby eliminating the cavity with a native side chain rather than solvent. Thus, both cavity hydration and structure relaxation are mechanisms for cavity elimination under pressure, and which is dominant is determined by details of the energy landscape. PMID:25918400

Rare-earth-ion-doped ultra-narrow-linewidth lasers on a silicon chip and applications to intra-laser-cavity optical sensing

NASA Astrophysics Data System (ADS)

Bernhardi, E. H.; de Ridder, R. M.; Wörhoff, K.; Pollnau, M.

2013-03-01

We report on diode-pumped distributed-feedback (DFB) and distributed-Bragg-reflector (DBR) channel waveguide lasers in Er-doped and Yb-doped Al2O3 on standard thermally oxidized silicon substrates. Uniform surface-relief Bragg gratings were patterned by laser-interference lithography and etched into the SiO2 top cladding. The maximum grating reflectivity exceeded 99%. Monolithic DFB and DBR cavities with Q-factors of up to 1.35×106 were realized. The Erdoped DFB laser delivered 3 mW of output power with a slope efficiency of 41% versus absorbed pump power. Singlelongitudinal- mode operation at a wavelength of 1545.2 nm was achieved with an emission line width of 1.70 0.58 kHz, corresponding to a laser Q-factor of 1.14×1011. Yb-doped DFB and DBR lasers were demonstrated at wavelengths near 1020 nm with output powers of 55 mW and a slope efficiency of 67% versus launched pump power. An Yb-doped dualwavelength laser was achieved based on the optical resonances induced by two local phase shifts in the DFB structure. A stable microwave signal at ~15 GHz with a -3-dB width of 9 kHz and a long-term frequency stability of +/- 2.5 MHz was created via the heterodyne photo-detection of the two laser wavelengths. By measuring changes in the microwave beat signal as the intra-cavity evanescent laser field interacts with micro-particles on the waveguide surface, we achieved real-time detection and accurate size measurement of single micro-particles with diameters ranging between 1 μm and 20 μm, which represents the typical size of many fungal and bacterial pathogens. A limit of detection of ~500 nm was deduced.

Frequency stabilization in nonlinear MEMS and NEMS oscillators

DOEpatents

Lopez, Omar Daniel; Antonio, Dario

2014-09-16

An illustrative system includes an amplifier operably connected to a phase shifter. The amplifier is configured to amplify a voltage from an oscillator. The phase shifter is operably connected to a driving amplitude control, wherein the phase shifter is configured to phase shift the amplified voltage and is configured to set an amplitude of the phase shifted voltage. The oscillator is operably connected to the driving amplitude control. The phase shifted voltage drives the oscillator. The oscillator is at an internal resonance condition, based at least on the amplitude of the phase shifted voltage, that stabilizes frequency oscillations in the oscillator.

Accoustic Localization of Breakdown in Radio Frequency Accelerating Cavities

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

Lane, Peter Gwin

Current designs for muon accelerators require high-gradient radio frequency (RF) cavities to be placed in solenoidal magnetic fields. These fields help contain and efficiently reduce the phase space volume of source muons in order to create a usable muon beam for collider and neutrino experiments. In this context and in general, the use of RF cavities in strong magnetic fields has its challenges. It has been found that placing normal conducting RF cavities in strong magnetic fields reduces the threshold at which RF cavity breakdown occurs. To aid the effort to study RF cavity breakdown in magnetic fields, it wouldmore » be helpful to have a diagnostic tool which can localize the source of breakdown sparks inside the cavity. These sparks generate thermal shocks to small regions of the inner cavity wall that can be detected and localized using microphones attached to the outer cavity surface. Details on RF cavity sound sources as well as the hardware, software, and algorithms used to localize the source of sound emitted from breakdown thermal shocks are presented. In addition, results from simulations and experiments on three RF cavities, namely the Aluminum Mock Cavity, the High-Pressure Cavity, and the Modular Cavity, are also given. These results demonstrate the validity and effectiveness of the described technique for acoustic localization of breakdown.« less

Acoustic localization of breakdown in radio frequency accelerating cavities

NASA Astrophysics Data System (ADS)

Lane, Peter

Current designs for muon accelerators require high-gradient radio frequency (RF) cavities to be placed in solenoidal magnetic fields. These fields help contain and efficiently reduce the phase space volume of source muons in order to create a usable muon beam for collider and neutrino experiments. In this context and in general, the use of RF cavities in strong magnetic fields has its challenges. It has been found that placing normal conducting RF cavities in strong magnetic fields reduces the threshold at which RF cavity breakdown occurs. To aid the effort to study RF cavity breakdown in magnetic fields, it would be helpful to have a diagnostic tool which can localize the source of breakdown sparks inside the cavity. These sparks generate thermal shocks to small regions of the inner cavity wall that can be detected and localized using microphones attached to the outer cavity surface. Details on RF cavity sound sources as well as the hardware, software, and algorithms used to localize the source of sound emitted from breakdown thermal shocks are presented. In addition, results from simulations and experiments on three RF cavities, namely the Aluminum Mock Cavity, the High-Pressure Cavity, and the Modular Cavity, are also given. These results demonstrate the validity and effectiveness of the described technique for acoustic localization of breakdown.

Theoretical exploration of competing phases of lattice Bose gases in a cavity

NASA Astrophysics Data System (ADS)

Liao, Renyuan; Chen, Huang-Jie; Zheng, Dong-Chen; Huang, Zhi-Gao

2018-01-01

We consider bosonic atoms loaded into optical lattices with cavity-mediated infinite-range interactions. Competing short- and global-range interactions cultivate a rich phase diagram. With a systematic field-theoretical perspective, we present an analytical construction of a global ground-state phase diagram. We find that the infinite-range interaction enhances the fluctuation of the number density. In the strong-coupling regime, we find four branches of elementary excitations, with two being "particlelike" and two being "holelike," and that the excitation gap becomes soft at the phase boundary between compressible phases and incompressible phases. We derive an effective theory describing compressible superfluid and supersolid states. To complement this perturbative study, we construct a self-consistent mean-field theory and find numerical results consistent with our theoretical analysis. We map out the phase diagram and find that a charge density wave may undergo a structure phase transition to a different charge density wave before it finally enters into the supersolid phase driven by increasing the hopping amplitude.

Direct Measurement of Large, Diffuse, Optical Structures

NASA Technical Reports Server (NTRS)

Saif, Babak N.; Keski-Kuha, Ritva; Feinberg, Lee; Wyant, J. C.; Atkinson, C.

2004-01-01

Digital Speckle Pattern Interferometry (DSPI) is a well-established method for the measurement of diffuse objects in experimental mechanics. DSPIs are phase shifting interferometers. Three or four bucket temporal phase shifting algorithms are commonly used to provide phase shifting. These algorithms are sensitive to vibrations and can not be used to measure large optical structures far away from the interferometer. In this research a simultaneous phase shifted interferometer, PhaseCam product of 4D Technology Corporation in Tucson Arizona, is modified to be a Simultaneous phase shifted Digital Speckle Pattern Interferometer (SDSPI). Repeatability, dynamic range, and accuracy of the SDSPI are characterized by measuring a 5 cm x 5 cm carbon fiber coupon.

HOM frequency control of SRF cavity in high current ERLs

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

Xu, Chen; Ben-Zvi, Ilan

The acceleration of high-current beam in Superconducting Radio Frequency (SRF) cavities is a challenging but essential for a variety of advanced accelerators. SRF cavities should be carefully designed to minimize the High Order Modes (HOM) power generated in the cavities by the beam current. The reduction of HOM power we demonstrate in a particular case can be quite large. This paper presents a method to systematically control the HOM resonance frequencies in the initial design phase to minimize the HOM power generation. This method is expected to be beneficial for the design of high SRF cavities addressing a variety ofmore » Energy Recovery Linac (ERL) applications.« less

HOM frequency control of SRF cavity in high current ERLs

DOE PAGES

Xu, Chen; Ben-Zvi, Ilan

2017-12-06

The acceleration of high-current beam in Superconducting Radio Frequency (SRF) cavities is a challenging but essential for a variety of advanced accelerators. SRF cavities should be carefully designed to minimize the High Order Modes (HOM) power generated in the cavities by the beam current. The reduction of HOM power we demonstrate in a particular case can be quite large. This paper presents a method to systematically control the HOM resonance frequencies in the initial design phase to minimize the HOM power generation. This method is expected to be beneficial for the design of high SRF cavities addressing a variety ofmore » Energy Recovery Linac (ERL) applications.« less

Phase I Study of IMRT and Molecular-Image Guided Adaptive Radiation Therapy for Advanced HNSCC

ClinicalTrials.gov

2016-10-27

Salivary Gland Squamous Cell Carcinoma; Stage II Salivary Gland Cancer; Stage II Squamous Cell Carcinoma of the Hypopharynx; Stage II Squamous Cell Carcinoma of the Lip and Oral Cavity; Stage II Squamous Cell Carcinoma of the Oropharynx; Stage II Verrucous Carcinoma of the Oral Cavity; Stage III Salivary Gland Cancer; Stage III Squamous Cell Carcinoma of the Hypopharynx; Stage III Squamous Cell Carcinoma of the Lip and Oral Cavity; Stage III Squamous Cell Carcinoma of the Oropharynx; Stage III Verrucous Carcinoma of the Oral Cavity; Stage IV Salivary Gland Cancer; Stage IV Squamous Cell Carcinoma of the Hypopharynx; Stage IV Squamous Cell Carcinoma of the Lip and Oral Cavity; Stage IV Squamous Cell Carcinoma of the Oropharynx; Stage IV Verrucous Carcinoma of the Oral Cavity

Generation of Ultrashort Pulses from Chromium - Forsterite Laser

NASA Astrophysics Data System (ADS)

Seas, Antonios

This thesis discusses the generation of ultrashort pulses from the chromium-doped forsterite laser, the various designs, construction and operation of forsterite laser systems capable of generating picosecond and femtosecond pulses in the near infrared. Various mode-locking techniques including synchronous optical pumping, active mode-locking, and self-mode-locking were successfully engineered and implemented. Active and synchronously pumped mode-locking using a three mirror, astigmatically compensated cavity design and a forsterite crystal with a figure of merit of 26 (FOM = alpha_{rm 1064nm} /alpha_{rm 1250nm }) generated pulses with FWHM of 49 and 260 ps, respectively. The tuning range of the mode-locked forsterite laser in both cases was determined to be in the order of 100 nm limited only by the dielectric coatings of the mirrors used in the cavity. The slope efficiency was measured to be 12.5% for synchronous pumping and 9.1% for active mode-locking. A four mirror astigmatically compensated cavity was found to be more appropriate for mode-locking. Active mode-locking using the four-mirror cavity generated pulses with FWHM of 31 ps. The pulsewidth was further reduced to 6 ps by using a forsterite crystal with a higher figure of merit (FOM = 39). Pulsewidth-bandwidth measurements indicated the presence of chirp in the output pulses. Numerical calculation of the phase characteristics of various optical materials indicated that a pair of prisms made of SF 14 optical glass can be used in the cavity in order to compensate for the chirp. The insertion of the prisms in the cavity resulted in a reduction of the pulsewidth from 6 ps down to 900 fs. Careful optimization of the laser cavity resulted in the generation of stable 90-fs pulses. Pulses as short as 60 fs were generated and self-mode-locked mode of operation using the Cr:forsterite laser was demonstrated for the first time. Pure self-mode-locking was next achieved generating 105-fs pulses tunable between 1230-1270 nm. Numerical calculations of the cubic phase characteristics of the prism pair used indicated that the pair of SF 14 prisms compensated for quadratic phase but introduced a large cubic phase term. Numerical evaluation of other optical glasses indicated that a pair of SFN 64 prisms can introduce the same quadratic phase as SF 14 prisms but introduce a smaller cubic phase. When the SF 14 prisms were replaced by SFN 64 prisms the pulsewidth was reduced to 50 fs. Great improvement was also observed in the stability of the self-mode-locked forsterite laser and in the ease of achieving mode-locking. Using the same experimental arrangement and a forsterite crystal with improved FOM the pulse width was reduced to 36 fs.

A novel phase retrieval method from three-wavelength in-line phase-shifting interferograms based on positive negative 2π phase shifts

NASA Astrophysics Data System (ADS)

Xu, Xiaoqing; Wang, Yawei; Ji, Ying; Xu, Yuanyuan; Xie, Ming

2018-01-01

A new method to extract quantitative phases for each wavelength from three-wavelength in-line phase-shifting interferograms is proposed. Firstly, seven interferograms with positive negative 2π phase shifts are sequentially captured by using the phase-shifting technique. Secondly, six dc-term suppressed intensities can be achieved by the use of the algebraic algorithm. Finally, the wrapped phases at the three wavelengths can be acquired simultaneously from these six interferograms add-subtracting by employing the trigonometric function method. The surface morphology with increased ambiguity-free range at synthetic beat wavelength can be obtained, while maintaining the low noise precision of the single wavelength measurement, by combining this method with three-wavelength phase unwrapping method. We illustrate the principle of this algorithm, and the simulated experiments of the spherical cap and the HeLa cell are conducted to prove our proposed method, respectively.

Expansion of linear range of Pound-Drever-Hall signal.

PubMed

Miyoki, Shinji; Telada, Souich; Uchiyama, Takashi

2010-10-01

We propose new solutions for expanding the linear signal range between the laser frequency deviation (or mirror position) and the voltage signal derived by the Pound-Drever-Hall (PDH) method for optical Fabry-Perot cavity resonance control. One solution is to perform not in-phase demodulation but near-Q-phase demodulation. Another solution is to take a suitable combination of signals demodulated by odd-harmonic modulation frequencies in the in phase. Although the PDH signal sensitivity will be diminished, the PDH signal linear range can be extended. From a practical standpoint, it is desirable that a sideband frequency for the PDH method is near the FP cavity resonance.

Quench dynamics of a disordered array of dissipative coupled cavities.

PubMed

Creatore, C; Fazio, R; Keeling, J; Türeci, H E

2014-09-08

We investigate the mean-field dynamics of a system of interacting photons in an array of coupled cavities in the presence of dissipation and disorder. We follow the evolution of an initially prepared Fock state, and show how the interplay between dissipation and disorder affects the coherence properties of the cavity emission, and show that these properties can be used as signatures of the many-body phase of the whole array.

3D measurement using combined Gray code and dual-frequency phase-shifting approach

NASA Astrophysics Data System (ADS)

Yu, Shuang; Zhang, Jing; Yu, Xiaoyang; Sun, Xiaoming; Wu, Haibin; Liu, Xin

2018-04-01

The combined Gray code and phase-shifting approach is a commonly used 3D measurement technique. In this technique, an error that equals integer multiples of the phase-shifted fringe period, i.e. period jump error, often exists in the absolute analog code, which can lead to gross measurement errors. To overcome this problem, the present paper proposes 3D measurement using a combined Gray code and dual-frequency phase-shifting approach. Based on 3D measurement using the combined Gray code and phase-shifting approach, one set of low-frequency phase-shifted fringe patterns with an odd-numbered multiple of the original phase-shifted fringe period is added. Thus, the absolute analog code measured value can be obtained by the combined Gray code and phase-shifting approach, and the low-frequency absolute analog code measured value can also be obtained by adding low-frequency phase-shifted fringe patterns. Then, the corrected absolute analog code measured value can be obtained by correcting the former by the latter, and the period jump errors can be eliminated, resulting in reliable analog code unwrapping. For the proposed approach, we established its measurement model, analyzed its measurement principle, expounded the mechanism of eliminating period jump errors by error analysis, and determined its applicable conditions. Theoretical analysis and experimental results show that the proposed approach can effectively eliminate period jump errors, reliably perform analog code unwrapping, and improve the measurement accuracy.

Cavity mode-width spectroscopy with widely tunable ultra narrow laser.

PubMed

Cygan, Agata; Lisak, Daniel; Morzyński, Piotr; Bober, Marcin; Zawada, Michał; Pazderski, Eugeniusz; Ciuryło, Roman

2013-12-02

We explore a cavity-enhanced spectroscopic technique based on determination of the absorbtion coefficient from direct measurement of spectral width of the mode of the optical cavity filled with absorbing medium. This technique called here the cavity mode-width spectroscopy (CMWS) is complementary to the cavity ring-down spectroscopy (CRDS). While both these techniques use information on interaction time of the light with the cavity to determine absorption coefficient, the CMWS does not require to measure very fast signals at high absorption conditions. Instead the CMWS method require a very narrow line width laser with precise frequency control. As an example a spectral line shape of P7 Q6 O₂ line from the B-band was measured with use of an ultra narrow laser system based on two phase-locked external cavity diode lasers (ECDL) having tunability of ± 20 GHz at wavelength range of 687 to 693 nm.

Etched-multilayer phase shifting masks for EUV lithography

DOEpatents

Chapman, Henry N.; Taylor, John S.

2005-04-05

A method is disclosed for the implementation of phase shifting masks for EUV lithography. The method involves directly etching material away from the multilayer coating of the mask, to cause a refractive phase shift in the mask. By etching into the multilayer (for example, by reactive ion etching), rather than depositing extra material on the top of the multilayer, there will be minimal absorption loss associated with the phase shift.

Constant frequency pulsed phase-locked loop measuring device

NASA Technical Reports Server (NTRS)

Yost, William T. (Inventor); Kushnick, Peter W. (Inventor); Cantrell, John H. (Inventor)

1993-01-01

A measuring apparatus is presented that uses a fixed frequency oscillator to measure small changes in the phase velocity ultrasonic sound when a sample is exposed to environmental changes such as changes in pressure, temperature, etc. The invention automatically balances electrical phase shifts against the acoustical phase shifts in order to obtain an accurate measurement of electrical phase shifts.

Controlling the opto-mechanics of a cantilever in an interferometer via cavity loss

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

Schmidsfeld, A. von, E-mail: avonschm@uos.de; Reichling, M., E-mail: reichling@uos.de

2015-09-21

In a non-contact atomic force microscope, based on interferometric cantilever displacement detection, the optical return loss of the system is tunable via the distance between the fiber end and the cantilever. We utilize this for tuning the interferometer from a predominant Michelson to a predominant Fabry-Pérot characteristics and introduce the Fabry-Pérot enhancement factor as a quantitative measure for multibeam interference in the cavity. This experimentally easily accessible and adjustable parameter provides a control of the opto-mechanical interaction between the cavity light field and the cantilever. The quantitative assessment of the light pressure acting on the cantilever oscillating in the cavitymore » via the frequency shift allows an in-situ measurement of the cantilever stiffness with remarkable precision.« less

High sensitivity gas sensor based on high-Q suspended polymer photonic crystal nanocavity

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

Clevenson, Hannah, E-mail: hannahac@mit.edu; Desjardins, Pierre; Gan, Xuetao

2014-06-16

We present high-sensitivity, multi-use optical gas sensors based on a one-dimensional photonic crystal cavity. These devices are implemented in versatile, flexible polymer materials which swell when in contact with a target gas, causing a measurable cavity length change. This change causes a shift in the cavity resonance, allowing precision measurements of gas concentration. We demonstrate suspended polymer nanocavity sensors and the recovery of sensors after the removal of stimulant gas from the system. With a measured quality factor exceeding 10{sup 4}, we show measurements of gas concentration as low as 600 parts per million (ppm) and an experimental sensitivity ofmore » 10 ppm; furthermore, we predict detection levels in the parts-per-billion range for a variety of gases.« less

Observation of an optical spring with a beam splitter.

PubMed

Cripe, Jonathan; Danz, Baylee; Lane, Benjamin; Lorio, Mary Catherine; Falcone, Julia; Cole, Garrett D; Corbitt, Thomas

2018-05-01

We present the experimental observation of an optical spring without the use of an optical cavity. The optical spring is produced by interference at a beam splitter and, in principle, does not have the damping force associated with optical springs created in detuned cavities. The experiment consists of a Michelson-Sagnac interferometer (with no recycling cavities) with a partially reflective GaAs microresonator as the beam splitter that produces the optical spring. Our experimental measurements at input powers of up to 360 mW show the shift of the optical spring frequency as a function of power and are in excellent agreement with theoretical predictions. In addition, we show that the optical spring is able to keep the interferometer stable and locked without the use of external feedback.

Stimulated photon emission and two-photon Raman scattering in a coupled-cavity QED system

PubMed Central

Li, C.; Song, Z.

2016-01-01

We study the scattering problem of photon and polariton in a one-dimensional coupled-cavity system. Analytical approximate analysis and numerical simulation show that a photon can stimulate the photon emission from a polariton through polariton-photon collisions. This observation opens the possibility of photon-stimulated transition from insulating to radiative phase in a coupled-cavity QED system. Inversely, we also find that a polariton can be generated by a two-photon Raman scattering process. This paves the way towards single photon storage by the aid of atom-cavity interaction. PMID:26877252

Time Harmonic Two-Dimensional Cavity Scar Statistics: Convex Mirrors and Bowtie

DOE PAGES

Warne, Larry Kevin; Jorgenson, Roy Eberhardt; Kotulski, Joseph Daniel; ...

2011-02-10

Here, this article examines the localization of time harmonic high-frequency modal fields in two-dimensional cavities along periodic paths between opposing sides of the cavity. The cases where these orbits lead to unstable localized modes are known as scars. This article examines the enhancements for these unstable orbits when the opposing mirrors are convex, constructing the high-frequency field in the scar region using elliptic cylinder coordinates in combination with a random reflection phase from the outer chaotic region. Finally, the enhancements when the cavity is symmetric as well as asymmetric about the orbit are examined.

Absolute Definition of Phase Shift in the Elastic Scattering of a Particle from Compound Systems

NASA Technical Reports Server (NTRS)

Temkin, A.

1961-01-01

The projection of the target wave function on the total wave function of a scattered particle interacting with the target system is used to define an absolute phase shift including any multiples of pi. With this definition of the absolute phase shift, one can prove rigorously in the limit of zero energy for s-wave electrons scattered from atomic hydrogen that the triplet phase shift must approach a nonzero multiple of pi. One can further show that at least one pi of this phase shift is not connected with the existence of a bound state of the H- ion.

Investigating Solutions to Wind Washing Issues in Two-Story Florida Homes, Phase 2

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

Withers, Charles R.; Kono, Jamie

2015-04-13

With U.S. Department of Energy goals of reducing existing home energy use by 30% and new home energy use by 50%, it is imperative to focus on several energy efficiency measures, including the quality of air and thermal barriers. This report provides results from a second-phase research study of a phenomenon generally referred to as wind washing. Wind washing is the movement of unconditioned air around or through building thermal barriers in such a way as to diminish or nullify the intended thermal performance. In some cases, thermal and air barriers are installed very poorly or not at all, andmore » air can readily move from unconditioned attic spaces into quasi-conditioned interstitial spaces. This study focused on the impact of poorly sealed and insulated floor cavities adjacent to attic spaces in Florida homes. In these cases, unconditioned attic air can be transferred into floor cavities through pathways driven by natural factors such as wind, or by thermal differences between the floor cavity and the attic. Air can also be driven into a floor cavity through mechanical forces imposed by return duct leakage in the floor cavity.« less

Phase-contrast scanning transmission electron microscopy.

PubMed

Minoda, Hiroki; Tamai, Takayuki; Iijima, Hirofumi; Hosokawa, Fumio; Kondo, Yukihito

2015-06-01

This report introduces the first results obtained using phase-contrast scanning transmission electron microscopy (P-STEM). A carbon-film phase plate (PP) with a small center hole is placed in the condenser aperture plane so that a phase shift is introduced in the incident electron waves except those passing through the center hole. A cosine-type phase-contrast transfer function emerges when the phase-shifted scattered waves interfere with the non-phase-shifted unscattered waves, which passed through the center hole before incidence onto the specimen. The phase contrast resulting in P-STEM is optically identical to that in phase-contrast transmission electron microscopy that is used to provide high contrast for weak phase objects. Therefore, the use of PPs can enhance the phase contrast of the STEM images of specimens in principle. The phase shift resulting from the PP, whose thickness corresponds to a phase shift of π, has been confirmed using interference fringes displayed in the Ronchigram of a silicon single crystal specimen. The interference fringes were found to abruptly shift at the edge of the PP hole by π. © The Author 2015. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Heralded quantum controlled-phase gates with dissipative dynamics in macroscopically distant resonators

NASA Astrophysics Data System (ADS)

Qin, Wei; Wang, Xin; Miranowicz, Adam; Zhong, Zhirong; Nori, Franco

2017-07-01

Heralded near-deterministic multiqubit controlled-phase gates with integrated error detection have recently been proposed by Borregaard et al. [Phys. Rev. Lett. 114, 110502 (2015), 10.1103/PhysRevLett.114.110502]. This protocol is based on a single four-level atom (a heralding quartit) and N three-level atoms (operational qutrits) coupled to a single-resonator mode acting as a cavity bus. Here we generalize this method for two distant resonators without the cavity bus between the heralding and operational atoms. Specifically, we analyze the two-qubit controlled-Z gate and its multiqubit-controlled generalization (i.e., a Toffoli-like gate) acting on the two-lowest levels of N qutrits inside one resonator, with their successful actions being heralded by an auxiliary microwave-driven quartit inside the other resonator. Moreover, we propose a circuit-quantum-electrodynamics realization of the protocol with flux and phase qudits in linearly coupled transmission-line resonators with dissipation. These methods offer a quadratic fidelity improvement compared to cavity-assisted deterministic gates.

Dynamics of Superradiant Lasers

NASA Astrophysics Data System (ADS)

Thompson, James

2014-05-01

A superradiant laser has been shown to operate with less than one photon on average inside of the optical cavity. In this regime, almost all of the phase information of the laser is stored in the atoms rather than the cavity field. As a result, the laser's phase is highly insensitive to both technical and fundamental thermal cavity mirror vibrations. This vibration noise presently limits the coherence of the best lasers as well as the precision of the optical lattice clocks that these lasers interrogate. We have explored the physics of superradiant lasers utilizing Raman transitions between hyperfine states in rubidium to mimic narrow optical transitions. In this talk, we will discuss the amplitude stability of our superradiant Raman laser, and the dynamics of phase synchronization in our system. We will also consider the prospects for future superradiant lasers that would lase on the same highly-forbidden transitions used in optical lattice clocks. We acknowledge support from DARPA QUASAR, ARO, NIST, and the NSF PFC.

Tunable, high-repetition-rate, dual-signal-wavelength femtosecond optical parametric oscillator based on BiB3O6

NASA Astrophysics Data System (ADS)

Meng, Xianghao; Wang, Zhaohua; Tian, Wenlong; Fang, Shaobo; Wei, Zhiyi

2018-01-01

We have demonstrated a high-repetition-rate tunable femtosecond dual-signal-wavelength optical parametric oscillator (OPO) based on BiB3O6 (BiBO) crystal, synchronously pumped by a frequency-doubled mode-locked Yb:KGW laser. The cavity is simple since no dispersion compensators are used in the cavity. The wavelength range of dual-signal is widely tunable from 710 to 1000 nm. Tuning is accomplished by rotating phase-matching angle of BiBO, and optimizing cavity length and output coupler. Using a 3.75 W pump laser, the maximum average dual-signal output power is 760 mW at 707 and 750 nm, leading to a conversion efficiency of 20.3% not taking into account the idler power. Our experimental results show a non-critical phase-matching configuration pumped by a high peak power laser source. The operation of the dual-signal benefits from the balance of phase matching and group velocity mismatching between the two signals.

Influence of OPD in wavelength-shifting interferometry

NASA Astrophysics Data System (ADS)

Wang, Hongjun; Tian, Ailing; Liu, Bingcai; Dang, Juanjuan

2009-12-01

Phase-shifting interferometry is a powerful tool for high accuracy optical measurement. It operates by change the optical path length in the reference arm or test arm. This method practices by move optical device. So it has much problem when the optical device is very large and heavy. For solve this problem, the wavelength-shifting interferometry was put forwarded. In wavelength-shifting interferometry, the phase shifting angle was achieved by change the wavelength of optical source. The phase shifting angle was decided by wavelength and OPD (Optical Path Difference) between test and reference wavefront. So the OPD is an important factor to measure results. But in measurement, because the positional error and profile error of under testing optical element is exist, the phase shifting angle is different in different test point when wavelength scanning, it will introduce phase shifting angle error, so it will introduce optical surface measure error. For analysis influence of OPD on optical surface error, the relation between surface error and OPD was researched. By simulation, the relation between phase shifting error and OPD was established. By analysis, the error compensation method was put forward. After error compensation, the measure results can be improved to great extend.

Influence of OPD in wavelength-shifting interferometry

NASA Astrophysics Data System (ADS)

Wang, Hongjun; Tian, Ailing; Liu, Bingcai; Dang, Juanjuan

2010-03-01

Phase-shifting interferometry is a powerful tool for high accuracy optical measurement. It operates by change the optical path length in the reference arm or test arm. This method practices by move optical device. So it has much problem when the optical device is very large and heavy. For solve this problem, the wavelength-shifting interferometry was put forwarded. In wavelength-shifting interferometry, the phase shifting angle was achieved by change the wavelength of optical source. The phase shifting angle was decided by wavelength and OPD (Optical Path Difference) between test and reference wavefront. So the OPD is an important factor to measure results. But in measurement, because the positional error and profile error of under testing optical element is exist, the phase shifting angle is different in different test point when wavelength scanning, it will introduce phase shifting angle error, so it will introduce optical surface measure error. For analysis influence of OPD on optical surface error, the relation between surface error and OPD was researched. By simulation, the relation between phase shifting error and OPD was established. By analysis, the error compensation method was put forward. After error compensation, the measure results can be improved to great extend.

Effect of low temperature baking on niobium cavities

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

Peter Kneisel; Ganapati Myneni; William Lanford

A low temperature (100 C-150 C) ''in situ'' baking under ultra-high vacuum has been successfully applied as final preparation of niobium RF cavities by several laboratories over the last few years. The benefits reported consist mainly of an improvement of the cavity quality factor and a recovery from the so-called ''Q-drop'' without field emission at high field. A series of experiments with a CEBAF single cell cavity have been carried out at Jefferson Lab to carefully investigate the effect of baking at progressively higher temperatures for a fixed time on all the relevant material parameters. Measurements of the cavity qualitymore » factor in the temperature range 1.37K-280K and resonant frequency shift between 6K-9.3K provide information about the surface resistance, energy gap, penetration depth and mean free path. The experimental data have been analyzed with the complete BCS theory of superconductivity using a modified version of the computer code originally written by J. Halbritter [1] . Small niobium samples inserted in the cavity during its surface preparation were analyzed with respect to their hydrogen content with a Nuclear Reaction Analysis (NRA). The single cell cavity has been tested at three different temperatures before and after baking to gain some insight on thermal conductivity and Kapitza resistance and the data are compared with different models. This paper describes the results from these experiments and comments on the existing models to explain the effect of baking on the performance of niobium RF cavities.« less

Assessing the measurement of aerosol single scattering albedo by Cavity Attenuated Phase-Shift Single Scattering Monitor (CAPS PMssa)

NASA Astrophysics Data System (ADS)

Perim de Faria, Julia; Bundke, Ulrich; Onasch, Timothy B.; Freedman, Andrew; Petzold, Andreas

2016-04-01

The necessity to quantify the direct impact of aerosol particles on climate forcing is already well known; assessing this impact requires continuous and systematic measurements of the aerosol optical properties. Two of the main parameters that need to be accurately measured are the aerosol optical depth and single scattering albedo (SSA, defined as the ratio of particulate scattering to extinction). The measurement of single scattering albedo commonly involves the measurement of two optical parameters, the scattering and the absorption coefficients. Although there are well established technologies to measure both of these parameters, the use of two separate instruments with different principles and uncertainties represents potential sources of significant errors and biases. Based on the recently developed cavity attenuated phase shift particle extinction monitor (CAPS PM_{ex) instrument, the CAPS PM_{ssa instrument combines the CAPS technology to measure particle extinction with an integrating sphere capable of simultaneously measuring the scattering coefficient of the same sample. The scattering channel is calibrated to the extinction channel, such that the accuracy of the single scattering albedo measurement is only a function of the accuracy of the extinction measurement and the nephelometer truncation losses. This gives the instrument an accurate and direct measurement of the single scattering albedo. In this study, we assess the measurements of both the extinction and scattering channels of the CAPS PM_{ssa through intercomparisons with Mie theory, as a fundamental comparison, and with proven technologies, such as integrating nephelometers and filter-based absorption monitors. For comparison, we use two nephelometers, a TSI 3563 and an Aurora 4000, and two measurements of the absorption coefficient, using a Particulate Soot Absorption Photometer (PSAP) and a Multi Angle Absorption Photometer (MAAP). We also assess the indirect absorption coefficient measurement from the CAPS PM_{ssa (calculated as the difference from the measured extinction and scattering). The study was carried out in the laboratory with controlled particle generation systems. We used both light absorbing aerosols (Regal 400R pigment black from Cabot Corp. and colloidal graphite - Aquadag - from Agar Scientific) and purely scattering aerosols (ammonium sulphate and polystyrene latex spheres), covering single scattering albedo values from approximately 0.4 to 1.0. A new truncation angle correction for the CAPS PM_{ssa integrated sphere is proposed.

Investigation of an Ultrafast Harmonic Resonant RF Kicker

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

Huang, Yulu

An Energy Recovery Linac (ERL) based multi-turn electron Circulator Cooler Ring (CCR) is envisaged in the proposed Jefferson Lab Electron Ion Collider (JLEIC) to cool the ion bunches with high energy (55 MeV), high current (1.5 A), high repetition frequency (476.3 MHz), high quality magnetized electron bunches. A critical component in this scheme is a pair of ultrafast kickers for the exchange of electron bunches between the ERL and the CCR. The ultrafast kicker should operate with the rise and fall time in less than 2.1 ns, at the repetition rate of ~10s MHz, and should be able to runmore » continuously during the whole period of cooling. These -and-fall time being combined together, are well beyond the state-of-art of traditional pulsed power supplies and magnet kickers. To solve this technical challenge, an alternative method is to generate this high repetition rate, fast rise-and-fall time short pulse continuous waveform by summing several finite number of (co)sine waves at harmonic frequencies of the kicking repetition frequency, and these harmonic modes can be generated by the Quarter Wave Resonater (QWR) based multifrequency cavities. Assuming the recirculator factor is 10, 10 harmonic modes (from 47.63 MHz to 476.3 MHz) with proper amplitudes and phases, plus a DC offset are combined together, a continuous short pulse waveform with the rise-and-fall time in less than 2.1 ns, repetition rate of 47.63 MHz waveform can be generated. With the compact and matured technology of QWR cavities, the total cost of both hardware development and operation can be reduced to a modest level. Focuse on the technical scheme, three main topics will be discussed in this thesis: the synthetization of the kicking pulse, the design and optimization of the deflecting QWR multi-integer harmonic frequency resonator and the fabrication and bench measurements of a half scale copper prototype. In the kicking pulse synthetization part, we begin with the Fourier Series expansion of an ideal square pulse, and get a Flat-Top waveform which will give a uniform kick over the bunch length of the kicked electron bunches, thus the transverse emittance of these kicked electron bunches can be maintained. By using two identical kickers with the betatron phase advance of 180 degree or its odd multiples, the residual kick voltage wave slopes at the unkicked bunch position will be totally cancelled out. Flat-Top waveform combined with two kicker scheme, the transverse emittance of the cooling electron bunches will be conserved during the whole injection, recirculation, and ejection processes. In the cavity design part, firstly, the cavity geometry is optimized to get high transverse shunt impedance thus less than 100 W of RF losses on the cavity wall can be achieved for all these 10 harmonic modes. To support all these 10 harmonic modes, group of four QWRs are adopted with the mode distribution of 5:3:1:1. In the multi-frequency cavities such as the five-mode-cavity and the three-mode-cavity, tunings are required to achieve the design frequencies for each mode. Slight segments of taper design on the inner conductor help to get the frequencies to be exactly on the odd harmonic modes. Stub tuners equal to the number of resonant modes are inserted to the outer conductor wall to compensate the frequency shifts due manufacturing errors and other perturbations during the operation such as the change of the cavity temperature. Single loop couple is designed for all harmonic modes in each cavity. By adjusting its loop size, position and rotation, it is possible to get the fundamental mode critical coupled and other higher harmonic modes slightly over coupled. A broadband circulator will be considered for absorbing the reflected power. Finally in this part, multipole field components due to the asymmetric cylindrical structure around the beam axis of the cavity as well as the beam-induced higher order mode (HOM) issues will be analyzed and discussed in this thesis. A half-scale copper prototype cavity (resonant frequencies from 95.26 MHz to 857.34 MHz) was fabricated to validate the electromagnetic characteristics. With this half scale prototype, the tuning processes of multiple harmonic frequencies, unloaded quality factor measurements of each mode, and bead-pull measurements are performed. The bench measurement results matched well with the simulation results, which have validated our cavity design and construction methods. Finally, a simple mode combining experiment with five separate signal generators was performed on this prototype cavity and the desired fast rise/fall time (1.2 ns), high repetition rate (95.26 MHz) waveform was captured, which finally proved our design of this ultrafast harmonic kicker.« less

Photon Counting as a Probe of Superfluidity in a Two-Band Bose-Hubbard System Coupled to a Cavity Field

NASA Astrophysics Data System (ADS)

Rajaram, Sara; Trivedi, Nandini

2013-12-01

We show that photon number measurement can be used to detect superfluidity for a two-band Bose-Hubbard model coupled to a cavity field. The atom-photon coupling induces transitions between the two internal atomic levels and results in entangled polaritonic states. In the presence of a cavity field, we find different photon numbers in the Mott-insulating versus superfluid phases, providing a method of distinguishing the atomic phases by photon counting. Furthermore, we examine the dynamics of the photon field after a rapid quench to zero atomic hopping by increasing the well depth. We find a robust correlation between the field’s quench dynamics and the initial superfluid order parameter, thereby providing a novel and accurate method of determining the order parameter.

Coherent single-atom superradiance

NASA Astrophysics Data System (ADS)

Kim, Junki; Yang, Daeho; Oh, Seung-hoon; An, Kyungwon

2018-02-01

Superradiance is a quantum phenomenon emerging in macroscopic systems whereby correlated single atoms cooperatively emit photons. Demonstration of controlled collective atom-field interactions has resulted from the ability to directly imprint correlations with an atomic ensemble. Here we report cavity-mediated coherent single-atom superradiance: Single atoms with predefined correlation traverse a high–quality factor cavity one by one, emitting photons cooperatively with the N atoms that have already gone through the cavity (N represents the number of atoms). Enhanced collective photoemission of N-squared dependence was observed even when the intracavity atom number was less than unity. The correlation among single atoms was achieved by nanometer-precision position control and phase-aligned state manipulation of atoms by using a nanohole-array aperture. Our results demonstrate a platform for phase-controlled atom-field interactions.

Theory of remote entanglement via quantum-limited phase-preserving amplification

NASA Astrophysics Data System (ADS)

Silveri, Matti; Zalys-Geller, Evan; Hatridge, Michael; Leghtas, Zaki; Devoret, Michel H.; Girvin, S. M.

2016-06-01

We show that a quantum-limited phase-preserving amplifier can act as a which-path information eraser when followed by heterodyne detection. This "beam splitter with gain" implements a continuous joint measurement on the signal sources. As an application, we propose heralded concurrent remote entanglement generation between two qubits coupled dispersively to separate cavities. Dissimilar qubit-cavity pairs can be made indistinguishable by simple engineering of the cavity driving fields providing further experimental flexibility and the prospect for scalability. Additionally, we find an analytic solution for the stochastic master equation, a quantum filter, yielding a thorough physical understanding of the nonlinear measurement process leading to an entangled state of the qubits. We determine the concurrence of the entangled states and analyze its dependence on losses and measurement inefficiencies.

Knowledge and risk perception of oral cavity and oropharyngeal cancer among non-medical university students.

PubMed

Osazuwa-Peters, Nosayaba; Tutlam, Nhial T

2016-01-28

To assess non-medical university students' knowledge and perceived risk of developing oral cavity and oropharyngeal cancer. A cross-sectional survey was conducted among non-medical students of a private Midwestern university in the United States in May 2012. Questionnaire assessed demographic information and contained 21 previously validated questions regarding knowledge and perceived risk of developing oral cavity and oropharyngeal cancer. Knowledge scale was categorized into low and high. Risk level was estimated based on smoking, drinking, and sexual habits. Bivariate associations between continuous and categorical variables were assessed using Pearson correlation and Chi-square tests, respectively. The response rate was 87% (100 out of 115 students approached). Eighty-one percent (81%) had low oral cavity and oropharyngeal cancer knowledge; and only 2% perceived that their oral cavity and oropharyngeal cancer risk was high. Risk perception was negatively correlated with age at sexual debut, r (64) = -0.26, p = 0.037; one-way ANOVA showed a marginally significant association between risk perception and number of sexual partners, F(4, 60) = 2.48, p = 0.05. There was no significant association between knowledge and perception of risk; however, oral cavity and oropharyngeal cancer knowledge was significantly associated with frequency of prevention of STDs (p < 0.05). Although 86% had heard about oral cavity and oropharyngeal cancer, only 18% had heard of oral mouth examination, and 7% of these reported ever having an oral cavity and oropharyngeal cancer exam. Oral cavity and oropharyngeal cancer knowledge and risk perception is low among this student population. Since oral cavity and oropharyngeal cancer incidence is increasingly shifting towards younger adults, interventions must be tailored to this group in order to improve prevention and control.

Migratory phase of Litomosoides sigmodontis filarial infective larvae is associated with pathology and transient increase of S100A9 expressing neutrophils in the lung

PubMed Central

Pionnier, Nicolas; Vallarino-Lhermitte, Nathaly; Lefoulon, Emilie; Nieguitsila, Adélaïde; Specht, Sabine; Carlin, Leo M.; Martin, Coralie

2017-01-01

Filarial infections are tropical diseases caused by nematodes of the Onchocercidae family such as Mansonella perstans. The infective larvae (L3) are transmitted into the skin of vertebrate hosts by blood-feeding vectors. Many filarial species settle in the serous cavities including M. perstans in humans and L. sigmodontis, a well-established model of filariasis in mice. L. sigmodontis L3 migrate to the pleural cavity where they moult into L4 around day 9 and into male and female adult worms around day 30. Little is known of the early phase of the parasite life cycle, after the L3 is inoculated in the dermis by the vector and enters the afferent lymphatic vessels and before the moulting processes in the pleural cavity. Here we reveal a pulmonary phase associated with lung damage characterized by haemorrhages and granulomas suggesting L3 reach the lung via pulmonary capillaries and damage the endothelium and parenchyma by crossing them to enter the pleural cavity. This study also provides evidence for a transient inflammation in the lung characterized by a very early recruitment of neutrophils associated with high expression levels of S100A8 and S100A9 proteins. PMID:28486498

Non-stationary and relaxation phenomena in cavity-assisted quantum memories

NASA Astrophysics Data System (ADS)

Veselkova, N. G.; Sokolov, I. V.

2017-12-01

We investigate the non-stationary and relaxation phenomena in cavity-assisted quantum memories for light. As a storage medium we consider an ensemble of cold atoms with standard Lambda-scheme of working levels. Some theoretical aspects of the problem were treated previously by many authors, and recent experiments stimulate more deep insight into the ultimate ability and limitations of the device. Since quantum memories can be used not only for the storage of quantum information, but also for a substantial manipulation of ensembles of quantum states, the speed of such manipulation and hence the ability to write and retrieve the signals of relatively short duration becomes important. In our research we do not apply the so-called bad cavity limit, and consider the memory operation of the signals whose duration is not much larger than the cavity field lifetime, accounting also for the finite lifetime of atomic coherence. In our paper we present an effective approach that makes it possible to find the non-stationary amplitude and phase behavior of strong classical control field, that matches the desirable time profile of both the envelope and the phase of the retrieved quantized signal. The phase properties of the retrieved quantized signals are of importance for the detection and manipulation of squeezing, entanglement, etc by means of optical mixing and homodyning.

A photothermal Mach-Zehnder interferometer for measuring caffeine and proteins in aqueous solutions using external cavity quantum cascade lasers

NASA Astrophysics Data System (ADS)

Kristament, Christian; Schwaighofer, Andreas; Montemurro, Milagros; Lendl, Bernhard

2018-02-01

One of the advantages of mid-IR spectroscopy in biomedical research lies in its capability to provide direct information on the secondary structure of proteins in their natural, often aqueous, environment. One impediment of direct absorption measurements in the correspondent spectral region is the strong absorbance of the native solvent (H2O). In this regard, the advent of broadly-tunable external cavity quantum cascade lasers (EC-QCL) allowed to significantly increasing the optical path length employed in transmission measurements due to their high spectral power densities. Low measured S/N ratios were improved by elaborated data analysis protocols that corrected mechanical flaws in the tuning mechanism of ECQCLs and allow for S/N ratios comparable to research grade FTIR spectrometers. Recent development of new optical set-ups outpacing direct absorption measurements led to further advancements. We present a dedicated Mach-Zehnder interferometer for photothermal measurements in balanced detection mode. In this highly sensitive design, the interferometer is illuminated by a HeNe laser to detect the refractive index change induced by the heat insertion of the EC-QCL. Here, we present photothermal phase shift interferometry measurements of caffeine in ethanol as well as casein in water. Further, the dependency of the signal amplitude on varying modulation frequencies was investigated for different liquids.

Optical diagnostics in the oral cavity: an overview.

PubMed

Wilder-Smith, P; Holtzman, J; Epstein, J; Le, A

2010-11-01

As the emphasis shifts from damage mitigation to disease prevention or reversal of early disease in the oral cavity, the need for sensitive and accurate detection and diagnostic tools become more important. Many novel and emergent optical diagnostic modalities for the oral cavity are becoming available to clinicians with a variety of desirable attributes including: (i) non-invasiveness, (ii) absence of ionizing radiation, (iii) patient-friendliness, (iv) real-time information (v) repeatability, and (vi) high-resolution surface and subsurface images. In this article, the principles behind optical diagnostic approaches, their feasibility and applicability for imaging soft and hard tissues, and their potential usefulness as a tool in the diagnosis of oral mucosal lesions, dental pathologies, and other dental applications will be reviewed. The clinical applications of light-based imaging technologies in the oral cavity and of their derivative devices will be discussed to provide the reader with a comprehensive understanding of emergent diagnostic modalities. © 2010 John Wiley & Sons A/S.

Experimental investigation into vortex structure and pressure drop across microcavities in 3D integrated electronics

NASA Astrophysics Data System (ADS)

Renfer, Adrian; Tiwari, Manish K.; Brunschwiler, Thomas; Michel, Bruno; Poulikakos, Dimos

2011-09-01

Hydrodynamics in microcavities with cylindrical micropin fin arrays simulating a single layer of a water-cooled electronic chip stack is investigated experimentally. Both inline and staggered pin arrangements are investigated using pressure drop and microparticle image velocimetry (μPIV) measurements. The pressure drop across the cavity shows a flow transition at pin diameter-based Reynolds numbers ( Re d ) ~200. Instantaneous μPIV, performed using a pH-controlled high seeding density of tracer microspheres, helps visualize vortex structure unreported till date in microscale geometries. The post-transition flow field shows vortex shedding and flow impingement onto the pins explaining the pressure drop increase. The flow fluctuations start at the chip outlet and shift upstream with increasing Re d . No fluctuations are observed for a cavity with pin height-to-diameter ratio h/ d = 1 up to Re d ~330; however, its pressure drop was higher than for a cavity with h/d = 2 due to pronounced influence of cavity walls.

Phase shifting interferometry based on a vibration sensor - feasibility study on elimination of the depth degeneracy

NASA Astrophysics Data System (ADS)

Lee, Seung Seok; Kim, Ju Ha; Choi, Eun Seo

2017-04-01

We proposed novel phase-shifting interferometry using a fiber-optic vibration sensor. The Doppler shift in the coiled fiber caused by vibrations can be used to detect the vibrations by using a fiber-optic interferometer. The principle can be applied to induce phase shifts. While applying vibrations to the coiled fiber at various vibration frequencies, we recorded the variations in the interference fringes. The interference fringe moved to longer wavelengths when a vibration frequency was increased from 38.00 to 38.40 kHz. Phase variations of 3.59 rad/kHz were obtained. The ability to accurately control the phase by using the vibrations in the coiled fiber was demonstrated by the elimination of the depth degeneracy using the complex signal generated by the phase-shifted interference fringes. Using vibrations to control phase shifting can be an acceptable alternative to conventional methods and can be applied to resolve the depth ambiguity in Fourier domain optical coherence tomography.

A Hybrid Method for Endocardial Contour Extraction of Right Ventricle in 4-Slices from 3D Echocardiography Dataset.

PubMed

Dawood, Faten A; Rahmat, Rahmita W; Kadiman, Suhaini B; Abdullah, Lili N; Zamrin, Mohd D

2014-01-01

This paper presents a hybrid method to extract endocardial contour of the right ventricular (RV) in 4-slices from 3D echocardiography dataset. The overall framework comprises four processing phases. In Phase I, the region of interest (ROI) is identified by estimating the cavity boundary. Speckle noise reduction and contrast enhancement were implemented in Phase II as preprocessing tasks. In Phase III, the RV cavity region was segmented by generating intensity threshold which was used for once for all frames. Finally, Phase IV is proposed to extract the RV endocardial contour in a complete cardiac cycle using a combination of shape-based contour detection and improved radial search algorithm. The proposed method was applied to 16 datasets of 3D echocardiography encompassing the RV in long-axis view. The accuracy of experimental results obtained by the proposed method was evaluated qualitatively and quantitatively. It has been done by comparing the segmentation results of RV cavity based on endocardial contour extraction with the ground truth. The comparative analysis results show that the proposed method performs efficiently in all datasets with overall performance of 95% and the root mean square distances (RMSD) measure in terms of mean ± SD was found to be 2.21 ± 0.35 mm for RV endocardial contours.

Spectral changes induced by a phase modulator acting as a time lens

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

Plansinis, B. W.; Donaldson, W. R.; Agrawal, G. P.

2015-07-06

We show both numerically and experimentally that a phase modulator, acting as a time lens in the Fourier-lens configuration, can induce spectral broadening, narrowing, or shifts, depending on the phase of the modulator cycle. These spectral effects depend on the maximum phase shift that can be imposed by the modulator. In our numerical simulations, pulse spectrum could be compressed by a factor of 8 for a 30 rad phase shift. Experimentally, spectral shifts over a 1.35 nm range and spectral narrowing and broadening by a factor of 2 were demonstrated using a lithium niobate phase modulator with a maximum phasemore » shift of 16 rad at a 10 GHz modulation frequency. All spectral changes were accomplished without employing optical nonlinear effects such as self- or cross-phase modulation.« less

Computational Study of an Axisymmetric Dual Throat Fluidic Thrust Vectoring Nozzle for a Supersonic Aircraft Application

NASA Technical Reports Server (NTRS)

Deere, Karen A.; Flamm, Jeffrey D.; Berrier, Bobby L.; Johnson, Stuart K.

2007-01-01

A computational investigation of an axisymmetric Dual Throat Nozzle concept has been conducted. This fluidic thrust-vectoring nozzle was designed with a recessed cavity to enhance the throat shifting technique for improved thrust vectoring. The structured-grid, unsteady Reynolds- Averaged Navier-Stokes flow solver PAB3D was used to guide the nozzle design and analyze performance. Nozzle design variables included extent of circumferential injection, cavity divergence angle, cavity length, and cavity convergence angle. Internal nozzle performance (wind-off conditions) and thrust vector angles were computed for several configurations over a range of nozzle pressure ratios from 1.89 to 10, with the fluidic injection flow rate equal to zero and up to 4 percent of the primary flow rate. The effect of a variable expansion ratio on nozzle performance over a range of freestream Mach numbers up to 2 was investigated. Results indicated that a 60 circumferential injection was a good compromise between large thrust vector angles and efficient internal nozzle performance. A cavity divergence angle greater than 10 was detrimental to thrust vector angle. Shortening the cavity length improved internal nozzle performance with a small penalty to thrust vector angle. Contrary to expectations, a variable expansion ratio did not improve thrust efficiency at the flight conditions investigated.

Cost-effective optical fiber pressure sensor based on intrinsic Fabry-Perot interferometric micro-cavities

NASA Astrophysics Data System (ADS)

Domingues, M. Fátima; Rodriguez, Camilo A.; Martins, Joana; Tavares, Cátia; Marques, Carlos; Alberto, Nélia; André, Paulo; Antunes, Paulo

2018-05-01

In this work, a cost-effective procedure to manufacture optical fiber pressure sensors is presented. This has a high relevance for integration in robotic exoskeletons or for gait plantar pressure monitoring within the physical rehabilitation scenarios, among other applications. The sensing elements are based on Fabry-Perot interferometric (FPI) micro-cavities, created from the recycling of optical fibers previously destroyed by the catastrophic fuse effect. To produce the pressure sensors, the fiber containing the FPI micro-cavities was embedded in an epoxy resin cylinder used as pressure transducer and responsible to transfer the pressure applied on its surface to the optical fiber containing the FPI micro-cavity. Before the embedding process, some FPI sensors were also characterized to strain variations. After that, the effect of the encapsulation of the FPI structure into the resin was assessed, from which a slight decrease on the FPI interferogram fringes visibility was verified, indicating a small increase in the micro-cavity length. Up on the sensors characterization, a linear dependence of the wavelength shift with the induced pressure was obtained, which leads to a maximum sensitivity of 59.39 ± 1.7 pm/kPa. Moreover, direct dependence of the pressure sensitivity with the micro-cavity volume and length was found.

High brightness electron accelerator

DOEpatents

Sheffield, Richard L.; Carlsten, Bruce E.; Young, Lloyd M.

1994-01-01

A compact high brightness linear accelerator is provided for use, e.g., in a free electron laser. The accelerator has a first plurality of acclerating cavities having end walls with four coupling slots for accelerating electrons to high velocities in the absence of quadrupole fields. A second plurality of cavities receives the high velocity electrons for further acceleration, where each of the second cavities has end walls with two coupling slots for acceleration in the absence of dipole fields. The accelerator also includes a first cavity with an extended length to provide for phase matching the electron beam along the accelerating cavities. A solenoid is provided about the photocathode that emits the electons, where the solenoid is configured to provide a substantially uniform magnetic field over the photocathode surface to minimize emittance of the electons as the electrons enter the first cavity.

Nucleate boiling performance evaluation of cavities at mesoscale level

DOE PAGES

Mu, Yu-Tong; Chen, Li; He, Ya-Ling; ...

2016-09-29

Nucleate boiling heat transfer (NBHT) from enhanced structures is an effective way to dissipate high heat flux. Here, a 3D multi-relaxation-time (MRT) phase-change lattice Boltzmann method in conjunction with conjugated heat transfer treatment is proposed and then applied to the study of cavities behaviours for nucleation on roughened surfaces for an entire ebullition cycle without introducing any artificial disturbance. The bubble departure diameter, departure frequency and total boiling heat transfer rate are also explored. We demonstrate that the cavity shapes show significant influence on the features of NBHT. The total heat transfer rate increases with the cavity mouth and cavitymore » base area while decreases with the increase in cavity bottom wall thickness. The cavity with low wetting can enhance the heat transfer and improve the bubble release frequency.« less

The ADMX Microwave Cavity: Present and future

NASA Astrophysics Data System (ADS)

Woollett, Nathan; ADMX Collaboration

2017-01-01

The Axion Dark Matter eXperiment (ADMX), a direct-detection axion search, uses a tunable resonant cavity to enhance axion to photon conversion rates to a detectable level when the cavity resonance matches the mass of the axion. It has successfully taken data in the 460 - 890 MHz frequency range and is now probing a similar range with much higher sensitivity. However the axion mass is unknown and may be at higher frequencies than the currently operating system. In anticipation of future runs with an increased mass range, ADMX is conducting extensive research and development of microwave cavities. These developments include photonic band-gap cavities, multi-vane cavities, partitioned cavities, in-phase coupled cavities, and superconducting hybrid cavities. Many of these projects are in different stages between simulations and testing of physical prototypes. The status and current objectives of these projects will be presented. Supported by DOE Grants DE-SC0010280, DE-FG02-96ER40956, DE-AC52-07NA27344, DE-AC03-76SF00098, the Heising-Simons Foundation and the LLNL, FNAL and PNNL LDRD program.

Phase retrieval from the phase-shift moiré fringe patterns in simultaneous dual-wavelength interferometry

NASA Astrophysics Data System (ADS)

Cheng, Jinlong; Gao, Zhishan; Bie, Shuyou; Dou, Yimeng; Ni, Ruihu; Yuan, Qun

2018-02-01

Simultaneous dual-wavelength interferometry (SDWI) could extend the measured range of each single-wavelength interferometry. The moiré fringe generated in SDWI indirectly represents the information of the measured long synthetic-wavelength ({λ }{{S}}) phase, thus the phase demodulation is rather arduous. To address this issue, we present a method to convert the moiré fringe pattern into a synthetic-wavelength interferogram (moiré to synthetic-wavelength, MTS). After the square of the moiré fringe pattern in the MTS method, the additive moiré pattern is turned into a multiplicative one. And the synthetic-wavelength interferogram could be obtained by a low-pass filtering in spectrum of the multiplicative moiré fringe pattern. Therefore, when the dual-wavelength interferometer is implemented with the π/2 phase shift at {λ }{{S}}, a sequence of synthetic-wavelength phase-shift interferograms with π/2 phase shift could be obtained after the MTS method processing on the captured moiré fringe patterns. And then the synthetic-wavelength phase could be retrieved by the conventional phase-shift algorithm. Compared with other methods in SDWI, the proposed MTS approach could reduce the restriction of the phase shift and frame numbers for the adoption of the conventional phase-shift algorithm. Following, numerical simulations are executed to evaluate the performance of the MTS method in processing time, frames of interferograms and the phase shift error compensation. And the necessary linear carrier for MTS method is less than 0.11 times of the traditional dual-wavelength spatial-domain Fourier transform method. Finally, the deviations for MTS method in experiment are 0.97% for a step with the height of 7.8 μm and 1.11% for a Fresnel lens with the step height of 6.2328 μm.

Device and method for noresonantly Raman shifting ultraviolet radiation

DOEpatents

Loree, Thomas R.; Barker, Dean L.

1979-01-01

A device and method for nonresonantly Raman shifting broad band uv excimer laser radiation, which enhances preselected Stokes signals by varying the pressure of the Raman scattering medium, the focal interaction length of the incident radiation within the Raman scattering medium and its power density level. Gaseous molecular H.sub.2, D.sub.2, CH.sub.4 (methane), HD and mixes thereof, and liquid N.sub.2 are used as the Raman scattering medium to frequency shift the outputs of high power KrF and ArF lasers. A cable fed discharge with an unstable resonant cavity configuration is utilized to produce the output laser power levels required for operation.

Light-Shifts of an Integrated Filter-Cell Rubidium Atomic Clock

DTIC Science & Technology

2015-05-25

the light-shift coefficient for two different rf- discharge lamps (i.e., a pure 87Rb lamp and a lamp filled with the natural Rb isotope abundance...for the Galileo Rb clock under the assumption of a natural (or 85Rb isotopically enriched) rf- discharge lamp for the Galileo clock. I...satellites [14]. 6.8347… GHz 85Rb Filter Cell Cell Resonance Photodiode Microwave Cavity 87Rb Discharge Lamp 87Rb & N2 Rb & Xe, Kr Optical Pumping 87Rb

In-line digital holography with phase-shifting Greek-ladder sieves

NASA Astrophysics Data System (ADS)

Xie, Jing; Zhang, Junyong; Zhang, Yanli; Zhou, Shenlei; Zhu, Jianqiang

2018-04-01

Phase shifting is the key technique in in-line digital holography, but traditional phase shifters have their own limitations in short wavelength regions. Here, phase-shifting Greek-ladder sieves with amplitude-only modulation are introduced into in-line digital holography, which are essentially a kind of diffraction lens with three-dimensional array diffraction-limited foci. In the in-line digital holographic experiment, we design two kinds of sieves by lithography and verify the validity of their phase-shifting function by measuring a 1951 U.S. Air Force resolution test target and three-dimensional array foci. With advantages of high resolving power, low cost, and no limitations at shorter wavelengths, phase-shifting Greek-ladder sieves have great potential in X-ray holography or biochemical microscopy for the next generation of synchrotron light sources.

Cryogenic test of the 4 K / 2 K insert for the ARIEL e-Linac cryomodule

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

Laxdal, R. E.; Ma, Y.; Harmer, P.

2014-01-29

The ARIEL project at TRIUMF requires a 50 MeV superconducting electron linac consisting of five nine cell 1.3 GHz cavities divided into three cryomodules with one, two and two cavities in each module respectively. LHe is distributed in parallel to each module at 4 K and at ∼1.2 bar. Each module has a cryogenic insert on board that receives the 4 K liquid and produces 2 K into a cavity phase separator. The module combines a 4 K phase separator, a plate and fin heat exchanger from DATE and a J-T valve expanding into the 2 K phase separator. Themore » unit also supplies 4 K liquid to thermal intercepts in the module in siphon loops that return the vaporized liquid to the 4 K reservoir. For testing purposes the unit is outfitted with a dummy 2 K phase separator and thermal intercepts with variable heaters that mimic the final heat loads in order to test the cryogenic performance. The design of the 4 K / 2 K insert, the results of the cold tests and a summary of the test infrastructure including cryogenics services will be presented.« less

Solving the jitter problem in microwave compressed ultrafast electron diffraction instruments: Robust sub-50 fs cavity-laser phase stabilization

PubMed Central

Otto, M. R.; René de Cotret, L. P.; Stern, M. J.; Siwick, B. J.

2017-01-01

We demonstrate the compression of electron pulses in a high-brightness ultrafast electron diffraction instrument using phase-locked microwave signals directly generated from a mode-locked femtosecond oscillator. Additionally, a continuous-wave phase stabilization system that accurately corrects for phase fluctuations arising in the compression cavity from both power amplification and thermal drift induced detuning was designed and implemented. An improvement in the microwave timing stability from 100 fs to 5 fs RMS is measured electronically, and the long-term arrival time stability (>10 h) of the electron pulses improves to below our measurement resolution of 50 fs. These results demonstrate sub-relativistic ultrafast electron diffraction with compressed pulses that is no longer limited by laser-microwave synchronization. PMID:28852686

Phase correction, phase resetting, and phase shifts after subliminal timing perturbations in sensorimotor synchronization.

PubMed

Repp, B H

2001-06-01

Recent studies of synchronized finger tapping have shown that perceptually subliminal phase shifts in an auditory sequence are rapidly compensated for in the motor activity (B. H. Repp, 2000a). Experiment 1 used a continuation-tapping task to confirm that this compensation is indeed a phase correction, not an adjustment of the central timekeeper period. Experiments 2-5 revealed that this phase correction occurs even when there is no ordinary sensorimotor asynchrony--when the finger taps are in antiphase or arbitrary phase relative to the auditory sequence (Experiments 2 and 3) or when the tap coinciding with the sequence phase shift is withheld (Experiments 4 and 5). The phase correction observed in the latter conditions was instantaneous, which suggests that phase resetting occurs when the motor activity is discontinuous. A prolonged phase shift suggestive of overcompensation was observed in some conditions, which poses a challenge to pure phase correction models.

Phase-Shift Interferometry with a Digital Photocamera

ERIC Educational Resources Information Center

Vannoni, Maurizio; Trivi, Marcelo; Molesini, Giuseppe

2007-01-01

A phase-shift interferometry experiment is proposed, working on a Twyman-Green optical configuration with additional polarization components. A guideline is provided to modern phase-shift interferometry, using concepts and laboratory equipment at the level of undergraduate optics courses. (Contains 5 figures.)

Improved detection sensitivity of D-mannitol crystalline phase content using differential spectral phase shift terahertz spectroscopy measurements.

PubMed

Allard, Jean-François; Cornet, Alain; Debacq, Christophe; Meurens, Marc; Houde, Daniel; Morris, Denis

2011-02-28

We report quantitative measurement of the relative proportion of δ- and β-D-mannitol crystalline phases inserted into polyethylene powder pellets, obtained by time-domain terahertz spectroscopy. Nine absorption bands have been identified from 0.2 THz to 2.2 THz. The best quantification of the δ-phase proportion is made using the 1.01 THz absorption band. Coherent detection allows using the spectral phase shift of the transmitted THz waveform to improve the detection sensitivity of the relative δ-phase proportion. We argue that differential phase shift measurements are less sensitive to samples' defects. Using a linear phase shift compensation for pellets of slightly different thicknesses, we were able to distinguish a 0.5% variation in δ-phase proportion.

Phase locking of a 1.5 Terahertz quantum cascade laser and use as a local oscillator in a heterodyne HEB receiver.

PubMed

Rabanus, D; Graf, U U; Philipp, M; Ricken, O; Stutzki, J; Vowinkel, B; Wiedner, M C; Walther, C; Fischer, M; Faist, J

2009-02-02

We demonstrate for the first time the closure of an electronic phase lock loop for a continuous-wave quantum cascade laser (QCL) at 1.5 THz. The QCL is operated in a closed cycle cryo cooler. We achieved a frequency stability of better than 100 Hz, limited by the resolution bandwidth of the spectrum analyser. The PLL electronics make use of the intermediate frequency (IF) obtained from a hot electron bolometer (HEB) which is downconverted to a PLL IF of 125 MHz. The coarse selection of the longitudinal mode and the fine tuning is achieved via the bias voltage of the QCL. Within a QCL cavity mode, the free-running QCL shows frequency fluctuations of about 5 MHz, which the PLL circuit is able to control via the Stark-shift of the QCL gain material. Temperature dependent tuning is shown to be nonlinear, and of the order of -16 MHz/K. Additionally we have used the QCL as local oscillator (LO) to pump an HEB and perform, again for the first time at 1.5 THz, a heterodyne experiment, and obtain a receiver noise temperature of 1741 K.

Phase Space Tweezers for Tailoring Cavity Fields by Quantum Zeno Dynamics

NASA Astrophysics Data System (ADS)

Raimond, J. M.; Sayrin, C.; Gleyzes, S.; Dotsenko, I.; Brune, M.; Haroche, S.; Facchi, P.; Pascazio, S.

2010-11-01

We discuss an implementation of quantum Zeno dynamics in a cavity quantum electrodynamics experiment. By performing repeated unitary operations on atoms coupled to the field, we restrict the field evolution in chosen subspaces of the total Hilbert space. This procedure leads to promising methods for tailoring nonclassical states. We propose to realize “tweezers” picking a coherent field at a point in phase space and moving it towards an arbitrary final position without affecting other nonoverlapping coherent components. These effects could be observed with a state-of-the-art apparatus.

Probing the limits of the rigid-intensity-shift model in differential-phase-contrast scanning transmission electron microscopy

NASA Astrophysics Data System (ADS)

Clark, L.; Brown, H. G.; Paganin, D. M.; Morgan, M. J.; Matsumoto, T.; Shibata, N.; Petersen, T. C.; Findlay, S. D.

2018-04-01

The rigid-intensity-shift model of differential-phase-contrast imaging assumes that the phase gradient imposed on the transmitted probe by the sample causes the diffraction pattern intensity to shift rigidly by an amount proportional to that phase gradient. This behavior is seldom realized exactly in practice. Through a combination of experimental results, analytical modeling and numerical calculations, using as case studies electron microscope imaging of the built-in electric field in a p-n junction and nanoscale domains in a magnetic alloy, we explore the breakdown of rigid-intensity-shift behavior and how this depends on the magnitude of the phase gradient and the relative scale of features in the phase profile and the probe size. We present guidelines as to when the rigid-intensity-shift model can be applied for quantitative phase reconstruction using segmented detectors, and propose probe-shaping strategies to further improve the accuracy.

Doppler radar with multiphase modulation of transmitted and reflected signal

NASA Technical Reports Server (NTRS)

Shores, Paul W. (Inventor); Griffin, John W. (Inventor); Kobayashi, Herbert S. (Inventor)

1989-01-01

A microwave radar signal is generated and split by a circulator. A phase shifter introduces a series of phase shifts into a first part of the split signal which is then transmitted by antenna. A like number of phase shifts is introduced by the phase shifter into the return signal from the target. The circulator delivers the phase shifted return signal and the leakage signal from the circulator to a mixer which generates an IF signal output at the Doppler frequency. The IF signal is amplified, filtered, counted per unit of time, and the result displayed to provide indications of target sense and range rate. An oscillator controls rate of phase shift in the transmitted and received radar signals and provides a time base for the counter. The phase shift magnitude increases may be continuous and linear or discrete functions of time.

The complex chemistry of outflow cavity walls exposed: the case of low-mass protostars

NASA Astrophysics Data System (ADS)

Drozdovskaya, Maria N.; Walsh, Catherine; Visser, Ruud; Harsono, Daniel; van Dishoeck, Ewine F.

2015-08-01

Complex organic molecules are ubiquitous companions of young low-mass protostars. Recent observations suggest that their emission stems, not only from the traditional hot corino, but also from offset positions. In this work, 2D physicochemical modelling of an envelope-cavity system is carried out. Wavelength-dependent radiative transfer calculations are performed and a comprehensive gas-grain chemical network is used to simulate the physical and chemical structure. The morphology of the system delineates three distinct regions: the cavity wall layer with time-dependent and species-variant enhancements; a torus rich in complex organic ices, but not reflected in gas-phase abundances and the remaining outer envelope abundant in simpler solid and gaseous molecules. Strongly irradiated regions, such as the cavity wall layer, are subject to frequent photodissociation in the solid phase. Subsequent recombination of the photoproducts leads to frequent reactive desorption, causing gas-phase enhancements of several orders of magnitude. This mechanism remains to be quantified with laboratory experiments. Direct photodesorption is found to be relatively inefficient. If radicals are not produced directly in the icy mantle, the formation of complex organics is impeded. For efficiency, a sufficient number of FUV photons needs to penetrate the envelope, and elevated cool dust temperatures need to enable grain-surface radical mobility. As a result, a high stellar luminosity and a sufficiently wide cavity favour chemical complexity. Furthermore within this paradigm, complex organics are demonstrated to have unique lifetimes and be grouped into early (formaldehyde, ketene, methanol, formic acid, methyl formate, acetic acid and glycolaldehyde) and late (acetaldehyde, dimethyl ether and ethanol) species.

Circadian rhythm phase shifts and endogenous free-running circadian period differ between African-Americans and European-Americans.

PubMed

Eastman, Charmane I; Suh, Christina; Tomaka, Victoria A; Crowley, Stephanie J

2015-02-11

Successful adaptation to modern civilization requires the internal circadian clock to make large phase shifts in response to circumstances (e.g., jet travel and shift work) that were not encountered during most of our evolution. We found that the magnitude and direction of the circadian clock's phase shift after the light/dark and sleep/wake/meal schedule was phase-advanced (made earlier) by 9 hours differed in European-Americans compared to African-Americans. European-Americans had larger phase shifts, but were more likely to phase-delay after the 9-hour advance (to phase shift in the wrong direction). The magnitude and direction of the phase shift was related to the free-running circadian period, and European-Americans had a longer circadian period than African-Americans. Circadian period was related to the percent Sub-Saharan African and European ancestry from DNA samples. We speculate that a short circadian period was advantageous during our evolution in Africa and lengthened with northern migrations out of Africa. The differences in circadian rhythms remaining today are relevant for understanding and treating the modern circadian-rhythm-based disorders which are due to a misalignment between the internal circadian rhythms and the times for sleep, work, school and meals.

Evidence of nonuniform phase-diffusion in a bad-cavity laser

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

Kuppens, S.J.M.; Exter, M.P. van; Duin, M. van

1995-07-01

The quantum-limited linewidth of a short HeNe 3.39-{micro}m laser was measured and seen to increase with increasing nonuniformity of the intracavity intensity distribution. Experiments were done inside as well as outside the bad-cavity regime; in this regime the polarization of the gain medium can not be adiabatically eliminated but acts as a memory. Good quantitative agreement with theory is obtained inside as well as outside the bad-cavity regime. The effect of nonuniformity is well described by the longitudinal Petermann K-factor. The bad-cavity and nonuniformity effects can be separated from each other as predicted by theory.

Enhanced efficiency of the second harmonic inhomogeneous component in an opaque cavity.

PubMed

Roppo, V; Raineri, F; Raj, R; Sagnes, I; Trull, J; Vilaseca, R; Scalora, M; Cojocaru, C

2011-05-15

In this Letter, we experimentally demonstrate the enhancement of the inhomogeneous second harmonic conversion in the opaque region of a GaAs cavity with efficiencies of the order of 0.1% at 612 nm, using 3 ps pump pulses having peak intensities of the order of 10 MW/cm(2). We show that the conversion efficiency of the inhomogeneous, phase-locked second harmonic component is a quadratic function of the cavity factor Q. © 2011 Optical Society of America

Implementation and Evaluation of Two Design Concepts of the Passive Ring Resonator Laser Gyroscope.

DTIC Science & Technology

1983-12-01

The cavity mirrors consist of 23 dielec- tric layers on a Zerodur substrate (Ref 1). The reflectivity of each mirror is 0.99995 (Ref 1). The...Conditions at the Cavity Input Mirror ...II1-8 6 Cavity Power Transmission vs. Frequency.. ........ II-10 7 Spatial Phase Distortion of the Reflected...32 16 Piano-Spherical Square vty.........II3 17 Astigmatism of a Spherical Mirror in a Ring 18 Case Is Circular-Circular Mode Match..........e...II

Passive radio frequency peak power multiplier

DOEpatents

Farkas, Zoltan D.; Wilson, Perry B.

1977-01-01

Peak power multiplication of a radio frequency source by simultaneous charging of two high-Q resonant microwave cavities by applying the source output through a directional coupler to the cavities and then reversing the phase of the source power to the coupler, thereby permitting the power in the cavities to simultaneously discharge through the coupler to the load in combination with power from the source to apply a peak power to the load that is a multiplication of the source peak power.

Experimental Measurements of Store Separation Using Dry Ice Models in a Subsonic Flow

DTIC Science & Technology

2011-03-01

slender bodies separating from rectangular cavities into low subsonic freestreams. The first part of their work presents the three phases of...aerodynamic problems relevant to separation of a thin body of revolution from rectangular cavities into subsonic or transonic flows” 13 [3]. Like many... cavity dimensions of 1.5 x 1.5 x 5.0 inches, resulting in a length-to-depth ratio of 3.33, slightly less the 3.6-6.0 used in previous research

Application of boundary element method to Stokes flows over a striped superhydrophobic surface with trapped gas bubbles

NASA Astrophysics Data System (ADS)

Ageev, A. I.; Golubkina, I. V.; Osiptsov, A. N.

2018-01-01

A slow steady flow of a viscous fluid over a superhydrophobic surface with a periodic striped system of 2D rectangular microcavities is considered. The microcavities contain small gas bubbles on the curved surface of which the shear stress vanishes. The general case is analyzed when the bubble occupies only a part of the cavity, and the flow velocity far from the surface is directed at an arbitrary angle to the cavity edge. Due to the linearity of the Stokes flow problem, the solution is split into two parts, corresponding to the flows perpendicular and along the cavities. Two variants of a boundary element method are developed and used to construct numerical solutions on the scale of a single cavity with periodic boundary conditions. By averaging these solutions, the average slip velocity and the slip length tensor components are calculated over a wide range of variation of governing parameters for the cases of a shear-driven flow and a pressure-driven channel flow. For a sufficiently high pressure drop in a microchannel of finite length, the variation of the bubble surface shift into the cavities induced by the streamwise pressure variation is estimated from numerical calculations.

An X-band phase-locked relativistic backward wave oscillator

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

Wu, Y.; Science and Technology on High Power Microwave Laboratory, Mianyang 621900; Li, Z. H.

2015-08-15

For the purpose of coherent high power microwave combining at high frequency band, an X-band phase-locked relativistic backward wave oscillator is presented and investigated. The phase-locking of the oscillator is accomplished by modulation of the electron beam before it reaches the oscillator. To produce a bunched beam with an acceptable injected RF power requirement, an overmoded input cavity is employed to provide initial density modulation. And a buncher cavity is introduced to further increase the modulation depth. When the beam enters the oscillator, the modulation depth is enough to lock the frequency and phase of the output microwave generated bymore » the oscillator. Particle-in-cell simulation shows that an input power of 90 kW is sufficient to lock the frequency and phase of 1.5 GW output microwave with locking bandwidth of 60 MHz.« less

Volume moiré tomography based on projection extraction by spatial phase shifting of double crossed gratings

NASA Astrophysics Data System (ADS)

Wang, Jia; Guo, Zhenyan; Song, Yang; Han, Jun

2018-01-01

To realize volume moiré tomography (VMT) for the real three-dimensional (3D) diagnosis of combustion fields, according to 3D filtered back projection (FBP) reconstruction algorithm, the radial derivatives of the projected phase should be measured firstly. In this paper, a simple spatial phase-shifting moiré deflectometry with double cross gratings is presented to measure the radial first-order derivative of the projected phase. Based on scalar diffraction theory, the explicit analytical intensity distributions of moiré patterns on different diffracted orders are derived, and the spatial shifting characteristics are analyzed. The results indicate that the first-order derivatives of the projected phase in two mutually perpendicular directions are involved in moiré patterns, which can be combined to compute the radial first-order derivative. And multiple spatial phase-shifted moiré patterns can be simultaneously obtained; the phase-shifted values are determined by the parameters of the system. A four-step phase-shifting algorithm is proposed for phase extraction, and its accuracy is proved by numerical simulations. Finally, the moiré deflectometry is used to measure the radial first-order derivative of projected phase of a propane flame with plane incident wave, and the 3D temperature distribution is reconstructed.

Nonadiabatic conditional geometric phase shift with NMR.

PubMed

Xiang-Bin, W; Keiji, M

2001-08-27

A conditional geometric phase shift gate, which is fault tolerant to certain types of errors due to its geometric nature, was realized recently via nuclear magnetic resonance (NMR) under adiabatic conditions. However, in quantum computation, everything must be completed within the decoherence time. The adiabatic condition makes any fast conditional Berry phase (cyclic adiabatic geometric phase) shift gate impossible. Here we show that by using a newly designed sequence of simple operations with an additional vertical magnetic field, the conditional geometric phase shift gate can be run nonadiabatically. Therefore geometric quantum computation can be done at the same rate as usual quantum computation.

The binding cavity of mouse major urinary protein is optimised for a variety of ligand binding modes

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

Pertinhez, Thelma A.; Ferrari, Elena; Casali, Emanuela

2009-12-25

{sup 15}N and {sup 1}HN chemical shift data and {sup 15}N relaxation studies have been used to characterise the binding of N-phenyl-naphthylamine (NPN) to mouse major urinary protein (MUP). NPN binds in the {beta}-barrel cavity of MUP, hydrogen bonding to Tyr120 and making extensive non-bonded contacts with hydrophobic side chains. In contrast to the natural pheromone 2-sec-butyl-4,5-dihydrothiazole, NPN binding gives no change to the overall mobility of the protein backbone of MUP. Comparison with 11 different ligands that bind to MUP shows a range of binding modes involving 16 different residues in the {beta}-barrel cavity. These finding justify why MUPmore » is able to adapt to allow for many successful binding partners.« less

Impact of optical feedback on current-induced polarization behavior of 1550 nm vertical-cavity surface-emitting lasers.

PubMed

Deng, Tao; Wu, Zheng-Mao; Xie, Yi-Yuan; Wu, Jia-Gui; Tang, Xi; Fan, Li; Panajotov, Krassimir; Xia, Guang-Qiong

2013-06-01

Polarization switching (PS) between two orthogonal linearly polarized fundamental modes is experimentally observed in commercial free-running 1550 nm vertical-cavity surface-emitting lasers (VCSELs) (Raycan). The characteristics of this PS are strongly modified after introducing a polarization-preserved (PP) or polarization-orthogonal (PO) optical feedback. Under the case that the external cavity is approximately 30 cm, the PP optical feedback results in the PS point shifting toward a lower injection current, and the region within which the two polarization modes coexist is enlarged with the increase of the PP feedback strength. Under too-strong PP feedback levels, the PS disappears. The impact of PO optical feedback on VCSEL polarization behavior is quite similar to that of PP optical feedback, but larger feedback strength is needed to obtain similar results.

A POSITIONAL DATA SYSTEM

DOEpatents

Forster, G.A.

1963-09-24

between master and slave synchros is described. A threephase a-c power source is connected to the stators of the synchros and an error detector is connected to the rotors of the synchros to measure the phasor difference therebetween. A phase shift network shifts the phase of one of the rotors 90 degrees and a demodulator responsive thereto causes the phasor difference signal of the rotors to shift phase 180 degrees whenever the 90 degree phase shifted signal goes negative. The phase shifted difference signal has a waveform which, with the addition of small values of resistance and capacitance, gives a substantially pure d-c output whose amplitude and polarity is proportional to the magnitude and direction of the difference in the angular positions of the synchro's rotors. (AEC)

Multiwavelength digital holography with wavelength-multiplexed holograms and arbitrary symmetric phase shifts.

PubMed

Tahara, Tatsuki; Otani, Reo; Omae, Kaito; Gotohda, Takuya; Arai, Yasuhiko; Takaki, Yasuhiro

2017-05-15

We propose multiwavelength in-line digital holography with wavelength-multiplexed phase-shifted holograms and arbitrary symmetric phase shifts. We use phase-shifting interferometry selectively extracting wavelength information to reconstruct multiwavelength object waves separately from wavelength-multiplexed monochromatic images. The proposed technique obtains systems of equations for real and imaginary parts of multiwavelength object waves from the holograms by introducing arbitrary symmetric phase shifts. Then, the technique derives each complex amplitude distribution of each object wave selectively and analytically by solving the two systems of equations. We formulate the algorithm in the case of an arbitrary number of wavelengths and confirm its validity numerically and experimentally in the cases where the number of wavelengths is two and three.

RF power recovery feedback circulator

DOEpatents

Sharamentov, Sergey I [Bolingbrook, IL

2011-03-29

A device and method for improving the efficiency of RF systems having a Reflective Load. In the preferred embodiment, Reflected Energy from a superconducting resonator of a particle accelerator is reintroduced to the resonator after the phase of the Reflected Energy is aligned with the phase of the Supply Energy from a RF Energy Source. In one embodiment, a Circulator is used to transfer Reflected Energy from the Reflective Load into a Phase Adjuster which aligns the phase of the Reflected Energy with that of the Supply Energy. The phase-aligned energy is then combined with the Supply Energy, and reintroduced into the Reflective Load. In systems having a constant phase shift, the Phase Adjuster may be designed to shift the phase of the Reflected Energy by a constant amount using a Phase Shifter. In systems having a variety (variable) phase shifts, a Phase Shifter controlled by a phase feedback loop comprising a Phase Detector and a Feedback Controller to account for the various phase shifts is preferable.

Quantum limits to gravity estimation with optomechanics

NASA Astrophysics Data System (ADS)

Armata, F.; Latmiral, L.; Plato, A. D. K.; Kim, M. S.

2017-10-01

We present a table-top quantum estimation protocol to measure the gravitational acceleration g by using an optomechanical cavity. In particular, we exploit the nonlinear quantum light-matter interaction between an optical field and a massive mirror acting as mechanical oscillator. The gravitational field influences the system dynamics affecting the phase of the cavity field during the interaction. Reading out such a phase carried by the radiation leaking from the cavity, we provide an estimate of the gravitational acceleration through interference measurements. Contrary to previous studies, having adopted a fully quantum description, we are able to propose a quantum analysis proving the ultimate bound to the estimability of the gravitational acceleration and verifying optimality of homodyne detection. Noticeably, thanks to the light-matter decoupling at the measurement time, no initial cooling of the mechanical oscillator is demanded in principle.

Effective spin physics in two-dimensional cavity QED arrays

NASA Astrophysics Data System (ADS)

Minář, Jiří; Güneş Söyler, Şebnem; Rotondo, Pietro; Lesanovsky, Igor

2017-06-01

We investigate a strongly correlated system of light and matter in two-dimensional cavity arrays. We formulate a multimode Tavis-Cummings (TC) Hamiltonian for two-level atoms coupled to cavity modes and driven by an external laser field which reduces to an effective spin Hamiltonian in the dispersive regime. In one-dimension we provide an exact analytical solution. In two-dimensions, we perform mean-field study and large scale quantum Monte Carlo simulations of both the TC and the effective spin models. We discuss the phase diagram and the parameter regime which gives rise to frustrated interactions between the spins. We provide a quantitative description of the phase transitions and correlation properties featured by the system and we discuss graph-theoretical properties of the ground states in terms of graph colourings using Pólya’s enumeration theorem.

Enhancing the Bandwidth of Gravitational-Wave Detectors with Unstable Optomechanical Filters

NASA Astrophysics Data System (ADS)

Miao, Haixing; Ma, Yiqiu; Zhao, Chunnong; Chen, Yanbei

2015-11-01

Advanced interferometric gravitational-wave detectors use optical cavities to resonantly enhance their shot-noise-limited sensitivity. Because of positive dispersion of these cavities—signals at different frequencies pick up different phases, there is a tradeoff between the detector bandwidth and peak sensitivity, which is a universal feature for quantum measurement devices having resonant cavities. We consider embedding an active unstable filter inside the interferometer to compensate the phase, and using feedback control to stabilize the entire system. We show that this scheme in principle can enhance the bandwidth without sacrificing the peak sensitivity. However, the unstable filter under our current consideration is a cavity-assisted optomechanical device operating in the instability regime, and the thermal fluctuation of the mechanical oscillator puts a very stringent requirement on the environmental temperature and the mechanical quality factor.

One-shot phase-shifting phase-grating interferometry with modulation of polarization: case of four interferograms.

PubMed

Rodriguez-Zurita, Gustavo; Meneses-Fabian, Cruz; Toto-Arellano, Noel-Ivan; Vázquez-Castillo, José F; Robledo-Sánchez, Carlos

2008-05-26

An experimental setup for optical phase extraction from 2-D interferograms using a one-shot phase-shifting technique able to achieve four interferograms with 90 degrees phase shifts in between is presented. The system uses a common-path interferometer consisting of two windows in the input plane and a phase grating in Fourier plane as its pupil. Each window has a birefringent wave plate attached in order to achieve nearly circular polarization of opposite rotations one respect to the other after being illuminated with a 45 degrees linear polarized beam. In the output, interference of the fields associated with replicated windows (diffraction orders) is achieved by a proper choice of the windows spacing with respect to the grating period. The phase shifts to achieve four interferograms simultaneously to perform phase-shifting interferometry can be obtained by placing linear polarizers on each diffraction orders before detection at an appropriate angle. Some experimental results are shown.

Resynchronization of circadian sleep-wake and temperature cycles in the squirrel monkey following phase shifts of the environmental light-dark cycle

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

Wexler, D.B.; Moore-ede, M.C.

1986-12-01

Circadian rhythms in physiological and behavioral functions gradually resynchronize after phase shifts in environmental time cues. In order to characterize the rate of circadian resynchronization in a diurnal primate model, the temperature, locomotor activity, and polygraphically determined sleep-wake states were monitored in squirrel monkeys before and after 8-h phase shifts of an environmental light-dark cycle of 12 h light and 12 h dark (LD 12:12). For the temperature rhythm, resynchronization took 4 d after phase delay shift and 5 d after phase advance shift; for the rest-activity cycle, resynchronization times were 3 d and 6 d, respectively. The activity acrophasemore » shifted more rapidly than the temperature acrophase early in the post-delay shift interval, but this internal desynchronization between rhythms disappeared during the course of resynchronization. Further study of the early resynchronization process requires emphasis on identifying evoked effects and measuring circadian pacemaker function. 13 references.« less

Resynchronization of circadian sleep-wake and temperature cycles in the squirrel monkey following phase shifts of the environmental light-dark cycle

NASA Technical Reports Server (NTRS)

Wexler, D. B.; Moore-Ede, M. C.

1986-01-01

Circadian rhythms in physiological and behavioral functions gradually resynchronize after phase shifts in environmental time cues. In order to characterize the rate of circadian resynchronization in a diurnal primate model, the temperature, locomotor activity, and polygraphically determined sleep-wake states were monitored in squirrel monkeys before and after 8-h phase shifts of an environmental light-dark cycle of 12 h light and 12 h dark (LD 12:12). For the temperature rhythm, resynchronization took 4 d after phase delay shift and 5 d after phase advance shift; for the rest-activity cycle, resynchronization times were 3 d and 6 d, respectively. The activity acrophase shifted more rapidly than the temperature acrophase early in the post-delay shift interval, but this internal desynchronization between rhythms disappeared during the course of resynchronization. Further study of the early resynchronization process requires emphasis on identifying evoked effects and measuring circadian pacemaker function.

Hemiparetic stepping to the beat: asymmetric response to metronome phase shift during treadmill gait.

PubMed

Pelton, Trudy A; Johannsen, Leif; Huiya Chen; Wing, Alan M

2010-06-01

Walking in time with a metronome is associated with improved spatiotemporal parameters in hemiparetic gait; however, the mechanism linking auditory and motor systems is poorly understood. Hemiparetic cadence control with metronome synchronization was examined to determine specific influences of metronome timing on treadmill walking. A within-participant experiment examined correction processes used to maintain heel strike synchrony with the beat by applying perturbations to the timing of a metronome. Eight chronic hemiparetic participants (mean age = 70 years; standard deviation = 12) were required to synchronize heel strikes with metronome pulses set according to each individual's comfortable speed (mean 0.4 m/s). During five 100-pulse trials, a fixed-phase baseline was followed by 4 unpredictable metronome phase shifts (20% of the interpulse interval), which amounted to 10 phase shifts on each foot. Infrared cameras recorded the motion of bilateral heel markers at 120 Hz. Relative asynchrony between heel strike responses and metronome pulses was used to index compensation for metronome phase shifts. Participants demonstrated compensation for phase shifts with convergence back to pre-phase shift asynchrony. This was significantly slower when the error occurred on the nonparetic side (requiring initial correction with the paretic limb) compared with when the error occurred on the paretic side (requiring initial nonparetic correction). Although phase correction of gait is slowed when the phase shift is delivered to the nonparetic side compared with the paretic side, phase correction is still present. This may underlie the utility of rhythmic auditory cueing in hemiparetic gait rehabilitation.

Measurement of Stress Distribution Around a Circular Hole in a Plate Under Bending Moment Using Phase-shifting Method with Reflective Polariscope Arrangement

NASA Astrophysics Data System (ADS)

Baek, Tae Hyun

Photoelasticity is one of the most widely used whole-field optical methods for stress analysis. The technique of birefringent coatings, also called the method of photoelastic coatings, extends the classical procedures of model photoelasticity to the measurement of surface strains in opaque models made of any structural material. Photoelastic phase-shifting method can be used for the determination of the phase values of isochromatics and isoclinics. In this paper, photoelastic phase-shifting technique and conventional Babinet-Soleil compensation method were utilized to analyze a specimen with a triangular hole and a circular hole under bending. Photoelastic phase-shifting technique is whole-field measurement. On the other hand, conventional compensation method is point measurement. Three groups of results were obtained by phase-shifting method with reflective polariscope arrangement, conventional compensation method and FEM simulation, respectively. The results from the first two methods agree with each other relatively well considering experiment error. The advantage of photoelastic phase-shifting method is that it is possible to measure the stress distribution accurately close to the edge of holes.

Highly uniform residual layers for arrays of 3D nanoimprinted cavities in Fabry-Pérot-filter-array-based nanospectrometers

NASA Astrophysics Data System (ADS)

Memon, Imran; Shen, Yannan; Khan, Abdullah; Woidt, Carsten; Hillmer, Hartmut

2016-04-01

Miniaturized optical spectrometers can be implemented by an array of Fabry-Pérot (FP) filters. FP filters are composed of two highly reflecting parallel mirrors and a resonance cavity. Each filter transmits a small spectral band (filter line) depending on its individual cavity height. The optical nanospectrometer, a miniaturized FP-based spectrometer, implements 3D NanoImprint technology for the fabrication of multiple FP filter cavities in a single process step. However, it is challenging to avoid the dependency of residual layer (RL) thickness on the shape of the printed patterns in NanoImprint. Since in a nanospectrometer the filter cavities vary in height between neighboring FP filters and, thus, the volume of each cavity varies causing that the RL varies slightly or noticeably between different filters. This is one of the few disadvantages of NanoImprint using soft templates such as substrate conformal imprint lithography which is used in this paper. The advantages of large area soft templates can be revealed substantially if the problem of laterally inhomogeneous RLs can be avoided or reduced considerably. In the case of the nanospectrometer, non-uniform RLs lead to random variations in the designed cavity heights resulting in the shift of desired filter lines. To achieve highly uniform RLs, we report a volume-equalized template design with the lateral distribution of 64 different cavity heights into several units with each unit comprising four cavity heights. The average volume of each unit is kept constant to obtain uniform filling of imprint material per unit area. The imprint results, based on the volume-equalized template, demonstrate highly uniform RLs of 110 nm thickness.

Parametric resonance in tunable superconducting cavities

NASA Astrophysics Data System (ADS)

Wustmann, Waltraut; Shumeiko, Vitaly

2013-05-01

We develop a theory of parametric resonance in tunable superconducting cavities. The nonlinearity introduced by the superconducting quantum interference device (SQUID) attached to the cavity and damping due to connection of the cavity to a transmission line are taken into consideration. We study in detail the nonlinear classical dynamics of the cavity field below and above the parametric threshold for the degenerate parametric resonance, featuring regimes of multistability and parametric radiation. We investigate the phase-sensitive amplification of external signals on resonance, as well as amplification of detuned signals, and relate the amplifier performance to that of linear parametric amplifiers. We also discuss applications of the device for dispersive qubit readout. Beyond the classical response of the cavity, we investigate small quantum fluctuations around the amplified classical signals. We evaluate the noise power spectrum both for the internal field in the cavity and the output field. Other quantum-statistical properties of the noise are addressed such as squeezing spectra, second-order coherence, and two-mode entanglement.

Insights to Superconducting Radio-Frequency Cavity Processing from First Principles Calculations and Spectroscopic Techniques

NASA Astrophysics Data System (ADS)

Ford, Denise Christine

Insights to the fundamental processes that occur during the manufacturing of niobium superconducting radio-frequency (SRF) cavities are provided via analyses of density functional theory calculations and Raman, infrared, and nuclear magnetic resonance (NMR) spectra. I show that during electropolishing fluorine is bound and released by the reaction of the acid components in the solution: HF + H2SO4 <-> HFSO3 + H2O. This result implies that new recipes can possibly be developed on the principle of controlled release of fluorine by a chemical reaction. I also show that NMR or Raman spectroscopy can be used to monitor the free fluorine when polishing with the standard electropolishing recipe. Density functional theory was applied to calculate the properties of common processing impurities---hydrogen, oxygen, nitrogen, and carbon---in the niobium. These impurities lower the superconducting transition temperature of niobium, and hydride precipitates are at best weakly superconducting. I modeled several of the niobium hydride phases relevant to SRF cavities, and explain the phase changes in the niobium hydrogen system based on the charge transfer between niobium and hydrogen and the strain field inside of the niobium. I also present evidence for a niobium lattice vacancy serving as a nucleation center for hydride phase formation. In considering the other chemical impurities in niobium, I show that the absorption of oxygen into a niobium lattice vacancy is preferred over the absorption of hydrogen, which indicates that oxygen can block these phase nucleation centers. I also show that dissolved oxygen atoms can trap dissolved hydrogen atoms to prevent niobium hydride phase formation. Nitrogen and carbon were studied in less depth, but behaved similarly to oxygen. Based on these results and a literature survey, I propose a mechanism for the success of the low-temperature anneal applied to niobium SRF cavities. Finally, I present the beginning of a model to describe magnetic impurities in niobium SRF cavities, which can cause a loss of local superconductivity. I calculated magnetic configurations of niobium hydrides and oxides, and show that stoichiometric hydride and oxide structures are nonmagnetic, but defective oxide structures retain local magnetic moments.

Insights to Superconducting Radio-Frequency Cavity Processing from First Principles Calculations and Spectroscopic Techniques

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

Ford, Denise Christine

Insights to the fundamental processes that occur during the manufacturing of niobium superconducting radio-frequency (SRF) cavities are provided via analyses of density functional theory calculations and Raman, infrared, and nuclear magnetic resonance (NMR) spectra. I show that during electropolishing fluorine is bound and released by the reaction of the acid components in the solution: HF + H 2SO 4 <-> HFSO 3 + H 2O. This result implies that new recipes can possibly be developed on the principle of controlled release of fluorine by a chemical reaction. I also show that NMR or Raman spectroscopy can be used to monitormore » the free fluorine when polishing with the standard electropolishing recipe. Density functional theory was applied to calculate the properties of common processing impurities – hydrogen, oxygen, nitrogen, and carbon – in the niobium. These impurities lower the superconducting transition temperature of niobium, and hydride precipitates are at best weakly superconducting. I modeled several of the niobium hydride phases relevant to SRF cavities, and explain the phase changes in the niobium hydrogen system based on the charge transfer between niobium and hydrogen and the strain field inside of the niobium. I also present evidence for a niobium lattice vacancy serving as a nucleation center for hydride phase formation. In considering the other chemical impurities in niobium, I show that the absorption of oxygen into a niobium lattice vacancy is preferred over the absorption of hydrogen, which indicates that oxygen can block these phase nucleation centers. I also show that dissolved oxygen atoms can trap dissolved hydrogen atoms to prevent niobium hydride phase formation. Nitrogen and carbon were studied in less depth, but behaved similarly to oxygen. Based on these results and a literature survey, I propose a mechanism for the success of the low-temperature anneal applied to niobium SRF cavities. Finally, I present the beginning of a model to describe magnetic impurities in niobium SRF cavities, which can cause a loss of local superconductivity. I calculated magnetic configurations of niobium hydrides and oxides, and show that stoichiometric hydride and oxide structures are nonmagnetic, but defective oxide structures retain local magnetic moments.« less

Method and apparatus for measuring butterfat and protein content using microwave absorption techniques

DOEpatents

Fryer, Michael O.; Hills, Andrea J.; Morrison, John L.

2000-01-01

A self calibrating method and apparatus for measuring butterfat and protein content based on measuring the microwave absorption of a sample of milk at several microwave frequencies. A microwave energy source injects microwave energy into the resonant cavity for absorption and reflection by the sample undergoing evaluation. A sample tube is centrally located in the resonant cavity passing therethrough and exposing the sample to the microwave energy. A portion of the energy is absorbed by the sample while another portion of the microwave energy is reflected back to an evaluation device such as a network analyzer. The frequency at which the reflected radiation is at a minimum within the cavity is combined with the scatter coefficient S.sub.11 as well as a phase change to calculate the butterfat content in the sample. The protein located within the sample may also be calculated in a likewise manner using the frequency, S.sub.11 and phase variables. A differential technique using a second resonant cavity containing a reference standard as a sample will normalize the measurements from the unknown sample and thus be self-calibrating. A shuttered mechanism will switch the microwave excitation between the unknown and the reference cavities. An integrated apparatus for measuring the butterfat content in milk using microwave absorption techniques is also presented.

Topological superfluids confined in a nanoscale slab geometry

NASA Astrophysics Data System (ADS)

Saunders, John

2013-03-01

Nanofluidic samples of superfluid 3He provide a route to explore odd-parity topological superfluids and their surface, edge and defect-bound excitations under well controlled conditions. We have cooled superfluid 3He confined in a precisely defined nano-fabricated cavity to well below 1 mK for the first time. We fingerprint the order parameter by nuclear magnetic resonance, exploiting a SQUID NMR spectrometer of exquisite sensitivity. We demonstrate that dimensional confinement, at length scales comparable to the superfluid Cooper-pair diameter, has a profound influence on the superfluid order of 3He. The chiral A-phase is stabilized at low pressures, in a cavity of height 650 nm. At higher pressures we observe 3He-B with a surface induced planar distortion. 3He-B is a time-reversal invariant topological superfluid, supporting gapless Majorana surface states. In the presence of the small symmetry breaking NMR static magnetic field we observe two possible B-phase states of the order parameter manifold, which can coexist as domains. Non-linear NMR on these states enables a measurement of the surface induced planar distortion, which determines the spectral weight of the surface excitations. The expected structure of the domain walls is such that, at the cavity surface, the line separating the two domains is predicted to host fermion zero modes, protected by symmetry and topology. Increasing confinement should stabilize new p-wave superfluid states of matter, such as the quasi-2D gapped A phase, which breaks time reversal symmetry, has a protected chiral edge mode, and may host half-quantum vortices with a Majorana zero-mode at the core. We discuss experimental progress toward this phase, through measurements on a 100 nm cavity. On the other hand, a cavity height of 1000 nm may stabilize a novel ``striped'' superfluid with spatially modulated order parameter. Supported by EPSRC (UK) GR/J022004/1 and European Microkelvin Consortium, FP7 grant 228464

Phase Shifting Capacity of the Circadian Pacemaker Determined by the SCN Neuronal Network Organization

PubMed Central

vanderLeest, Henk Tjebbe; Rohling, Jos H. T.; Michel, Stephan; Meijer, Johanna H.

2009-01-01

Background In mammals, a major circadian pacemaker that drives daily rhythms is located in the suprachiasmatic nuclei (SCN), at the base of the hypothalamus. The SCN receive direct light input via the retino-hypothalamic tract. Light during the early night induces phase delays of circadian rhythms while during the late night it leads to phase advances. The effects of light on the circadian system are strongly dependent on the photoperiod to which animals are exposed. An explanation for this phenomenon is currently lacking. Methodology and Principal Findings We recorded running wheel activity in C57 mice and observed large amplitude phase shifts in short photoperiods and small shifts in long photoperiods. We investigated whether these different light responses under short and long days are expressed within the SCN by electrophysiological recordings of electrical impulse frequency in SCN slices. Application of N-methyl-D-aspartate (NMDA) induced sustained increments in electrical activity that were not significantly different in the slices from long and short photoperiods. These responses led to large phase shifts in slices from short days and small phase shifts in slices from long days. An analysis of neuronal subpopulation activity revealed that in short days the amplitude of the rhythm was larger than in long days. Conclusions The data indicate that the photoperiodic dependent phase responses are intrinsic to the SCN. In contrast to earlier predictions from limit cycle theory, we observed large phase shifting responses in high amplitude rhythms in slices from short days, and small shifts in low amplitude rhythms in slices from long days. We conclude that the photoperiodic dependent phase responses are determined by the SCN and propose that synchronization among SCN neurons enhances the phase shifting capacity of the circadian system. PMID:19305510

Bistability in a hybrid optomechanical system: effect of a gain medium

NASA Astrophysics Data System (ADS)

Asghari Nejad, A.; Baghshahi, H. R.; Askari, H. R.

2017-11-01

In this paper, we investigate the optical bistability of a hybrid optomechanical system consisting of two coupled cavities: a bare optomechanical cavity (with an oscillating mirror at one end) and a traditional one. The traditional cavity is filled with an optical parametric amplifier (OPA), and an input pump laser is applied to it. The Hamiltonian of the system is written in a rotating frame. The dynamics of the system is driven by the quantum Langevin equations of motion. We demonstrate that the presence of an OPA can dramatically affect the type of stability of the optomechanical cavity. We show that it is possible to create a proper optical bistability for the optomechanical cavity by changing the gain coefficient of the OPA. Also, it is shown that changing the phase of the field driving the OPA has two different effects on the bistability region of the optomechanical cavity. Moreover, we show that by choosing a proper value for the detuning of the traditional cavity it is possible to observe a tristable behavior in the optomechanical cavity.

A three pulse phase response curve to three milligrams of melatonin in humans

PubMed Central

Burgess, Helen J; Revell, Victoria L; Eastman, Charmane I

2008-01-01

Exogenous melatonin is increasingly used for its phase shifting and soporific effects. We generated a three pulse phase response curve (PRC) to exogenous melatonin (3 mg) by administering it to free-running subjects. Young healthy subjects (n = 27) participated in two 5 day laboratory sessions, each preceded by at least a week of habitual, but fixed sleep. Each 5 day laboratory session started and ended with a phase assessment to measure the circadian rhythm of endogenous melatonin in dim light using 30 min saliva samples. In between were three days in an ultradian dim light (< 150 lux)–dark cycle (LD 2.5 : 1.5) during which each subject took one pill per day at the same clock time (3 mg melatonin or placebo, double blind, counterbalanced). Each individual's phase shift to exogenous melatonin was corrected by subtracting their phase shift to placebo (a free-run). The resulting PRC has a phase advance portion peaking about 5 h before the dim light melatonin onset, in the afternoon. The phase delay portion peaks about 11 h after the dim light melatonin onset, shortly after the usual time of morning awakening. A dead zone of minimal phase shifts occurred around the first half of habitual sleep. The fitted maximum advance and delay shifts were 1.8 h and 1.3 h, respectively. This new PRC will aid in determining the optimal time to administer exogenous melatonin to achieve desired phase shifts and demonstrates that using exogenous melatonin as a sleep aid at night has minimal phase shifting effects. PMID:18006583

Large Dispersive Shift of Cavity Resonance Induced by a Superconducting Flux Qubit in the Straddling Regime

NASA Astrophysics Data System (ADS)

Inomata, Kunihiro; Yamamoto, Tsuyoshi; Billangeon, Pierre-M.; Lin, Zhirong; Nakamura, Yasunobu; Tsai, Jaw-Shen; Koshino, Kazuki

2013-03-01

We demonstrate enhancement of the dispersive frequency shift in a coplanar waveguide resonator induced by a capacitively coupled superconducting flux qubit in the straddling regime. The magnitude of the observed shift, 80 MHz for the qubit-resonator detuning of 5 GHz, is quantitatively explained by the generalized Rabi model which takes into account the contribution of the qubit higher energy levels. By applying the enhanced dispersive shift to the qubit readout, we achieved 90 % contrast of the Rabi oscillations which is mainly limited by the energy relaxation of the qubit. We also discuss the qubit readout using a Josephson parametric amplifier. This work was supported by the MEXT Kakenhi ``Quantum Cybernetics'', the JSPS through its FIRST Program, and the NICT Commissioned Research.