Intraluminal laser atherectomy with ultrasound and electromagnetic guidance

Science.gov (United States)

Gregory, Kenton W.; Aretz, H. Thomas; Martinelli, Michael A.; LeDet, Earl G.; Hatch, G. F.; Gregg, Richard E.; Sedlacek, Tomas; Haase, Wayne C.

1991-05-01

The MagellanTM coronary laser atherectomy system is described. It uses high- resolution ultrasound imaging and electromagnetic sensing to provide real-time guidance and control of laser therapy in the coronary arteries. The system consists of a flexible catheter, an electromagnetic navigation antenna, a sensor signal processor and a computer for image processing and display. The small, flexible catheter combines an ultrasound transducer and laser delivery optics, aimed at the artery wall, and an electromagnetic receiving sensor. An extra-corporeal electromagnetic transmit antenna, in combination with catheter sensors, locates the position of the ultrasound and laser beams in the artery. Navigation and ultrasound data are processed electronically to produce real-time, transverse, and axial cross-section images of the artery wall at selected locations. By exploiting the ability of ultrasound to image beneath the surface of artery walls, it is possible to identify candidate treatment sites and perform safe radial laser debulking of atherosclerotic plaque with reduced danger of perforation. The utility of the system in plaque identification and ablation is demonstrated with imaging and experimental results.

Injection-controlled laser resonator

Science.gov (United States)

Chang, J.J.

1995-07-18

A new injection-controlled laser resonator incorporates self-filtering and self-imaging characteristics with an efficient injection scheme. A low-divergence laser signal is injected into the resonator, which enables the injection signal to be converted to the desired resonator modes before the main laser pulse starts. This injection technique and resonator design enable the laser cavity to improve the quality of the injection signal through self-filtering before the main laser pulse starts. The self-imaging property of the present resonator reduces the cavity induced diffraction effects and, in turn, improves the laser beam quality. 5 figs.

Determination of elastic modulus for hollow spherical shells via resonant ultrasound spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Ma, Xiaojun [Institute of Modern Physics, Fudan University, Shanghai 200433 (China); Research Center of Laser Fusion, CAEP, Mianyang 621900 (China); Tang, Xing; Wang, Zongwei [Research Center of Laser Fusion, CAEP, Mianyang 621900 (China); Chen, Qian; Qian, Menglu [Institute of Acoustic, Tongji University, Shanghai 200092 (China); Meng, Jie [Research Center of Laser Fusion, CAEP, Mianyang 621900 (China); Tang, Yongjian [Institute of Modern Physics, Fudan University, Shanghai 200433 (China); Research Center of Laser Fusion, CAEP, Mianyang 621900 (China); Shen, Hao [Institute of Modern Physics, Fudan University, Shanghai 200433 (China); Gao, Dangzhong, E-mail: dgaocn@163.com [Research Center of Laser Fusion, CAEP, Mianyang 621900 (China)

2017-04-15

Highlights: • The axisymmetric frequency equation of an isotropic hollow two-layer sphere is deduced by three dimension elasticity theory and global matrix method. • The simulated results demonstrate that the natural frequencies of a hollow sphere are more strongly dependent on Young’s modulus than Poisson's ratio. • The Young’s moduli of polymer capsules with an sub-millimeter inner radius are measured accurately with an uncertainty of ∼10%. - Abstract: The elastic property of a capsule is one of the essential parameters both in engineering applications and scientific understanding of material nature in inertial confinement fusion (ICF) experiments. The axisymmetric frequency equation of an isotropic hollow two-layer sphere is deduced by three dimension elasticity theory and global matrix method, and a combined resonant ultrasound spectroscopy(RUS), which consists of a piezoelectric-based resonant ultrasound spectroscopy(PZT-RUS) and a laser-based resonant ultrasound spectroscopy(LRUS), is developed for determining the elastic modulus of capsule. To understand the behavior of natural frequencies varying with elastic properties, the dependence of natural frequencies on Young’s modulus and Poisson’s ratio are calculated numerically. Some representative polymer capsules are measured using PZT-RUS and LRUS. Based on the theoretical and experimental results, the Young’s moduli of these capsules are measured accurately with an uncertainty of ∼10%.

Acoustic anomalies in the resonant ultrasound spectra of La2-x SrxCuO4

International Nuclear Information System (INIS)

Sarrao, J.L.; Lei, M.; Migliori, A.

1992-01-01

Resonant ultrasound spectroscopy is a novel technique for the simultaneous determination of a solid's elastic moduli. Measurements of the resonant ultrasound spectra of single crystals of La 2-x Sr x CuO 4 for several values of x are reported. Anomalies associated with the nonstoichiometric (x>0) doped superconductor have been observed. These anomalies indicate that the absence of short-wavelength translational invariance at the Brillouin-zone edge is being coupled into the zone center. Measurements of the stoichiometric (x=0) insulator will also be discussed. [This work was performed at Los Alamos National Laboratory under the auspices of the U.S. Department of Energy.

Evaluation of elastic properties of DLC layers using resonant ultrasound spectroscopy and AFM nanoindentation

Czech Academy of Sciences Publication Activity Database

Kocourek, Tomáš; Růžek, Michal; Landa, Michal; Jelínek, Miroslav; Mikšovský, Jan; Kopeček, Jaromír

2011-01-01

Roč. 205, č. 2 (2011), S67-S70 ISSN 0257-8972 R&D Projects: GA ČR(CZ) GA101/09/0702 Institutional research plan: CEZ:AV0Z10100522; CEZ:AV0Z20760514 Keywords : RUS-resonant ultrasound spectroscopy * PLD * diamond-like carbon * elastic properties * AFM nanoindentation Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.867, year: 2011

Candle soot nanoparticles-polydimethylsiloxane composites for laser ultrasound transducers

Science.gov (United States)

Chang, Wei-Yi; Huang, Wenbin; Kim, Jinwook; Li, Sibo; Jiang, Xiaoning

2015-10-01

Generation of high power laser ultrasound strongly demands the advanced materials with efficient laser energy absorption, fast thermal diffusion, and large thermoelastic expansion capabilities. In this study, candle soot nanoparticles-polydimethylsiloxane (CSNPs-PDMS) composite was investigated as the functional layer for an optoacoustic transducer with high-energy conversion efficiency. The mean diameter of the collected candle soot carbon nanoparticles is about 45 nm, and the light absorption ratio at 532 nm wavelength is up to 96.24%. The prototyped CSNPs-PDMS nano-composite laser ultrasound transducer was characterized and compared with transducers using Cr-PDMS, carbon black (CB)-PDMS, and carbon nano-fiber (CNFs)-PDMS composites, respectively. Energy conversion coefficient and -6 dB frequency bandwidth of the CSNPs-PDMS composite laser ultrasound transducer were measured to be 4.41 × 10-3 and 21 MHz, respectively. The unprecedented laser ultrasound transduction performance using CSNPs-PDMS nano-composites is promising for a broad range of ultrasound therapy applications.

Michelson interferometer with diffractively-coupled arm resonators in second-order Littrow configuration.

Science.gov (United States)

Britzger, Michael; Wimmer, Maximilian H; Khalaidovski, Alexander; Friedrich, Daniel; Kroker, Stefanie; Brückner, Frank; Kley, Ernst-Bernhard; Tünnermann, Andreas; Danzmann, Karsten; Schnabel, Roman

2012-11-05

Michelson-type laser-interferometric gravitational-wave (GW) observatories employ very high light powers as well as transmissively-coupled Fabry-Perot arm resonators in order to realize high measurement sensitivities. Due to the absorption in the transmissive optics, high powers lead to thermal lensing and hence to thermal distortions of the laser beam profile, which sets a limit on the maximal light power employable in GW observatories. Here, we propose and realize a Michelson-type laser interferometer with arm resonators whose coupling components are all-reflective second-order Littrow gratings. In principle such gratings allow high finesse values of the resonators but avoid bulk transmission of the laser light and thus the corresponding thermal beam distortion. The gratings used have three diffraction orders, which leads to the creation of a second signal port. We theoretically analyze the signal response of the proposed topology and show that it is equivalent to a conventional Michelson-type interferometer. In our proof-of-principle experiment we generated phase-modulation signals inside the arm resonators and detected them simultaneously at the two signal ports. The sum signal was shown to be equivalent to a single-output-port Michelson interferometer with transmissively-coupled arm cavities, taking into account optical loss. The proposed and demonstrated topology is a possible approach for future all-reflective GW observatory designs.

Noncontact ultrasonic nondestructive evaluation/inspection using laser generation and air coupled transducer

International Nuclear Information System (INIS)

Jhang, Kyung Young; Kim, Hong Joon; Cemiglia, Donatella; Djordjevic, Boro

2001-01-01

Ultrasonic MDE/I methods have been demonstrated as very effective tool in characterization of cracks and structural defects such as bond-line failures. Most of the ultrasonic testing is performed using conventional contact ultrasonic transducers that cannot be readily adapted to automation and field application. However, for large area inspection contact type is time consuming and as a result, it is important to develop a rapid and more efficient ultrasonic technique. In this paper, laser generation and air-coupled detection of ultrasound is proposed as a solution of non-contact method with no requirement of a coupling medium, and the bond quality of adhesively bonded and riveted aluminum lap splice joints is investigated as an application. A Q-switched Nd:YAG laser and a periodic transmission mask are used to generate a selected Lamb mode. The experimental show that multi-line laser source produces significant directed ultrasound and that the presence of defects can be detected reliably from the attenuation of signal amplitude. These results demonstrate that the proposed technique is well suitable and flexible for non-contact NDE/I applications.

Intraluminal ultrasound guidance of transverse laser coronary atherectomy

Science.gov (United States)

Aretz, H. Thomas; Martinelli, Michael A.; LeDet, Earl G.; Sedlacek, Tomas; Hatch, G. F.; Gregg, Richard E.

1990-07-01

A coronary laser atherectomy system combining laser delivery and ultrasonic imaging capability is described. The system is being developed by Intra-Sonix, Inc. to treat severe stenoses. The imaging system provides the clinician with the guidance needed to remove substantial plaque without perforation. The ultrasound transducers and laser optics are mounted in a small (less than 4 F), flexible catheter, that is deliverable over a standard guidewire (0.016 inch). The laser and ultrasound beams are directed at the artery wall to permit debulking of lesions and ultrasonic depth profiling of the tissue structure throughout the thickness of the artery. This allows the physician to determine the level of therapy to be applied and to monitor the plaque removal as the therapy progresses. The precise location of the ultrasound and laser beams in the artery is determined by a navigation system. Navigation data are processed electronically in conjunction with ultrasound data to produce real-time cross-sectional and longitudinal images of the artery wall at selected locations, which are updated as the catheter progresses through the vessel lumen. Results of in vitro tests on human atherosclerotic arteries and early in vivo experiments in a canine-human xenograft model showing image construction and radial laser delivery are discussed.

In-Source Laser Resonance Ionization at ISOL Facilities

CERN Document Server

Marsh, Bruce; Feddosseev, Valentin

Resonance ionization laser ion source development has been carried out at two radioactive ion beam facilities: ISOLDE (CERN, Switzerland) and the IGISOL facility (Jyvaskyla, Finland). The scope of the Resonance Ionization Laser Ion Source has been extended to 27 elements with the development of new three-step ionization schemes for Sb, Sc, Dy, Y and Au. The efficiencies were determined to be in the range of 2 - 20 %. Additionally, a new two-step ionization scheme has been developed for bismuth in an off-line atomic beam unit. The scheme relies on ionization via a strong and broad auto-ionizing resonance at an energy of 63196.79 cm$^{−1}$. This scheme may offer an improvement over the existing RILIS efficiency and will be more convenient for use during resonance ionization spectroscopy of Bi isotopes. The RILIS can be used as a spectroscopic tool to probe features such as the hyperfine structures and the isotope-shifts of radioisotopes with low production rates. By coupling a laser scanning process that dire...

Nonthermal effects of therapeutic ultrasound: the frequency resonance hypothesis.

Science.gov (United States)

Johns, Lennart D

2002-07-01

To present the frequency resonance hypothesis, a possible mechanical mechanism by which treatment with non-thermal levels of ultrasound stimulates therapeutic effects. The review encompasses a 4-decade history but focuses on recent reports describing the effects of nonthermal therapeutic levels of ultrasound at the cellular and molecular levels. A search of MEDLINE from 1965 through 2000 using the terms ultrasound and therapeutic ultrasound. The literature provides a number of examples in which exposure of cells to therapeutic ultrasound under nonthermal conditions modified cellular functions. Nonthermal levels of ultrasound are reported to modulate membrane properties, alter cellular proliferation, and produce increases in proteins associated with inflammation and injury repair. Combined, these data suggest that nonthermal effects of therapeutic ultrasound can modify the inflammatory response. The concept of the absorption of ultrasonic energy by enzymatic proteins leading to changes in the enzymes activity is not novel. However, recent reports demonstrating that ultrasound affects enzyme activity and possibly gene regulation provide sufficient data to present a probable molecular mechanism of ultrasound's nonthermal therapeutic action. The frequency resonance hypothesis describes 2 possible biological mechanisms that may alter protein function as a result of the absorption of ultrasonic energy. First, absorption of mechanical energy by a protein may produce a transient conformational shift (modifying the 3-dimensional structure) and alter the protein's functional activity. Second, the resonance or shearing properties of the wave (or both) may dissociate a multimolecular complex, thereby disrupting the complex's function. This review focuses on recent studies that have reported cellular and molecular effects of therapeutic ultrasound and presents a mechanical mechanism that may lead to a better understanding of how the nonthermal effects of ultrasound may be

An improved prism for use in laser resonators

Science.gov (United States)

Richards, J.

1981-08-01

The use of compound total internal reflection prisms rather than Porro prisms in polarisation coupled lasers is proposed. Performance advantages resulting from the use of these prisms include higher output without the need to bias the Pockels cell, ability to give a larger range of output coupling and independence of performance on the refractive index of the prism. In conventional Q-switched lasers the use of the prism at the Pockels cell end of the resonator instead of the usual 100% reflecting mirror also leads to some advantages including better hold-off, elimination of the need to bias the Pockels cell and insensitivity in one plane to angular misalignment.

Technology of discharge and laser resonators for high power CO2 lasers. Koshutsuryoku CO2 laser ni tsukawareru hoden reiki laser kyoshinki gijutsu

Energy Technology Data Exchange (ETDEWEB)

Takenaka, Y.; Kuzumoto, M. (Mitsubishi Electric Corp., Tokyo (Japan))

1994-03-20

This paper describes discharge excitation technology and resonator technology as basic technologies for high power CO2 lasers. As a result of progress in high-frequency power element techniques, the discharge excitation technology now generally uses laser excitation using AC discharge of capacity coupling type. Its representative example is silent discharge (SD) excitation. This is a system to excite laser by applying high voltages with as high frequency as 100 kHz to 1 MHz across a pair of electrodes covered with a dielectric material. The system maintains stability in discharge even if power supply voltage amplitude is modulated, and easily provides pulse outputs. Discharge excitation for diffusion cooled type CO2 laser generates a discharge in a gap with a gap length of about 2 mm, and can perform gas cooling by means of thermal conduction of gas, whereas a compact resonator can be fabricated. A resonator for the diffusion cooled type CO2 laser eliminates gas circulation and cooling systems, hence the device can be made more compact. A report has been given that several of these compact resonators were combined, from which a laser output of 85W was obtained by using RF discharge of 2kW. 43 refs., 21 figs.

Highly scalable, resonantly cladding-pumped, Er-doped fiber laser with record efficiency.

Science.gov (United States)

Dubinskii, M; Zhang, J; Ter-Mikirtychev, V

2009-05-15

We report the performance of a resonantly cladding-pumped, Yb-free, Er-doped fiber laser. We believe this is the first reported resonantly cladding-pumped fiber-Bragg-grating-based, Er-doped, large-mode-area (LMA) fiber laser. The laser, pumped by fiber-coupled InGaAsP/InP laser diode modules at 1,532.5 nm, delivers approximately 48 W of cw output at 1,590 nm. It is believed to be the highest power ever reported from a Yb-free Er-doped LMA fiber. This fully integrated laser also has the optical-to-optical efficiency of approximately 57%, to the best of our knowledge, the highest efficiency reported for cladding-pumped unidirectionally emitting Er-doped laser.

Generation of ultrasound in materials using continuous-wave lasers.

Science.gov (United States)

Caron, James N; DiComo, Gregory P; Nikitin, Sergei

2012-03-01

Generating and detecting ultrasound is a standard method of nondestructive evaluation of materials. Pulsed lasers are used to generate ultrasound remotely in situations that prohibit the use of contact transducers. The scanning rate is limited by the repetition rates of the pulsed lasers, ranging between 10 and 100 Hz for lasers with sufficient pulse widths and energies. Alternately, a high-power continuous-wave laser can be scanned across the surface, creating an ultrasonic wavefront. Since generation is continuous, the scanning rate can be as much as 4 orders of magnitude higher than with pulsed lasers. This paper introduces the concept, comparing the theoretical scanning speed with generation by pulsed laser. © 2012 Optical Society of America

The non-planar single-frequency ring laser with variable output coupling

Science.gov (United States)

Wu, Ke-ying; Yang, Su-hui; Wei, Guang-hui

2002-03-01

We put forward a novel non-planar single-frequency ring laser, which consists of a corner cube prism and a specially cut Porro prism made by Nd:YAG crystal. The relative angle between the corner cube and the Porro prism could be adjusted to control the output coupling of the laser resonator and the polarization-state of the output laser. A 1.06 μm single-frequency laser with 1 W output has been obtained.

Synchronisation in the phase model of three coupled lasers

International Nuclear Information System (INIS)

Kuznetsov, A P; Sataev, I R; Tyuryukina, L V; Chernyshov, N Yu

2014-01-01

The problem of synchronisation of three lasers is considered within the phase approximation. The domains of complete synchronisation, partial synchronisation, two-frequency resonant regimes, and three-frequency quasi-periodicity have been found using bifurcation analysis, the method of Lyapunov exponent maps, and construction of phase portraits. The differences in the properties of a three-element chain and ring, as well as the influence of the coupling type, are discussed. (control of laser radiation parameters)

Continuous-wave singly resonant optical parametric oscillator placed inside a ring laser

DEFF Research Database (Denmark)

Abitan, Haim; Buchhave, Preben

2003-01-01

A cw singly resonant optical parametric oscillator (SRO) was built and placed inside the cavity of a ring laser. The system consists of a diode-end-pumped Nd:YVO4 ring laser with intracavity periodically poled lithium niobate as the nonlinear gain medium of the SRO. When the laser was operated...... in a unidirectional mode, we obtained more than 520 mW of signal power in one beam. When the laser was operated in a bidirectional mode, we obtained 600 mW of signal power (300 mW in two separate beams). The power and the spectral features of the laser in the unidirectional and bidirectional modes were measured while...... the laser was coupled with the SRO. The results show that it is preferable to couple a SRO with a unidirectional ring laser....

Coupled-resonator optical waveguides

DEFF Research Database (Denmark)

Raza, Søren; Grgic, Jure; Pedersen, Jesper Goor

2010-01-01

Coupled-resonator optical waveguides hold potential for slow-light propagation of optical pulses. The dispersion properties may adequately be analyzed within the framework of coupled-mode theory. We extend the standard coupled-mode theory for such structures to also include complex-valued paramet......Coupled-resonator optical waveguides hold potential for slow-light propagation of optical pulses. The dispersion properties may adequately be analyzed within the framework of coupled-mode theory. We extend the standard coupled-mode theory for such structures to also include complex...

Review of magnetic resonance-guided focused ultrasound in the treatment of uterine fibroids

Directory of Open Access Journals (Sweden)

Pedro Felipe Magalhães Peregrino

Full Text Available Uterine leiomyoma is the most frequently occurring solid pelvic tumor in women during the reproductive period. Magnetic resonance-guided high-intensity focused ultrasound is a promising technique for decreasing menorrhagia and dysmenorrhea in symptomatic women. The aim of this study is to review the role of Magnetic resonance-guided high-intensity focused ultrasound in the treatment of uterine fibroids in symptomatic patients. We performed a review of the MEDLINE and Cochrane databases up to April 2016. The analysis and data collection were performed using the following keywords: Leiomyoma, High-Intensity Focused Ultrasound Ablation, Ultrasonography, Magnetic Resonance Imaging, Menorrhagia. Two reviewers independently performed a quality assessment; when there was a disagreement, a third reviewer was consulted. Nineteen studies of Magnetic resonance-guided high-intensity focused ultrasound-treated fibroid patients were selected. The data indicated that tumor size was reduced and that symptoms were improved after treatment. There were few adverse effects, and they were not severe. Some studies have reported that in some cases, additional sessions of Magnetic resonance-guided high-intensity focused ultrasound or other interventions, such as myomectomy, uterine artery embolization or even hysterectomy, were necessary. This review suggests that Magnetic resonance-guided high-intensity focused ultrasound is a safe and effective technique. However, additional evidence from future studies will be required before the technique can be recommended as an alternative treatment for fibroids.

Enhanced laser beam coupling to a plasma

International Nuclear Information System (INIS)

Steiger, A.D.; Woods, C.H.

1976-01-01

Density perturbations are induced in a heated plasma by means of a pair of oppositely directed, polarized laser beams of the same frequency. The wavelength of the density perturbations is equal to one half the wavelength of the laser beams. A third laser beam is linearly polarized and directed at the perturbed plasma along a line that is perpendicular to the direction of the two opposed beams. The electric field of the third beam is oriented to lie in the plane containing the three beams. The frequency of the third beam is chosen to cause it to interact resonantly with the plasma density perturbations, thereby efficiently coupling the energy of the third beam to the plasma. 10 claims, 2 figures

Ultrasound induced by CW laser cavitation bubbles

International Nuclear Information System (INIS)

Korneev, N; Montero, P Rodriguez; Ramos-Garcia, R; Ramirez-San-Juan, J C; Padilla-Martinez, J P

2011-01-01

The generation of ultrasound by a collapsing single cavitation bubble in a strongly absorbing liquid illuminated with a moderate power CW laser is described. The ultrasound shock wave is detected with hydrophone and interferometric device. To obtain a stronger pulse it is necessary to adjust a liquid absorption and a beam diameter. Their influence can be qualitatively understood with a simple model.

Laser resonant ionization spectroscopy and laser-induced resonant fluorescence spectra of samarium atom

International Nuclear Information System (INIS)

Jin, Changtai

1995-01-01

We have measured new high-lying levels of Sm atom by two-colour resonant photoionisation spectroscopy; we have observed the isotope shifts of Sm atom by laser-induced resonant fluorescence spectroscopy; the lifetime of eight low-lying levels of Sm atom were measured by using pulsed laser-Boxcar technique in atomic beam.

Resonator design and performance estimation for a space-based laser transmitter

Science.gov (United States)

Agrawal, Lalita; Bhardwaj, Atul; Pal, Suranjan; Kamalakar, J. A.

2006-12-01

Development of a laser transmitter for space applications is a highly challenging task. The laser must be rugged, reliable, lightweight, compact and energy efficient. Most of these features are inherently achieved by diode pumping of solid state lasers. Overall system reliability can further be improved by appropriate optical design of the laser resonator besides selection of suitable electro-optical and opto-mechanical components. This paper presents the design details and the theoretically estimated performance of a crossed-porro prism based, folded Z-shaped laser resonator. A symmetrically pumped Nd: YAG laser rod of 3 mm diameter and 60 mm length is placed in the gain arm with total input peak power of 1800 W from laser diode arrays. Electro-optical Q-switching is achieved through a combination of a polarizer, a fractional waveplate and LiNbO 3 Q-switch crystal (9 x 9 x 25 mm) placed in the feedback arm. Polarization coupled output is obtained by optimizing azimuth angle of quarter wave plate placed in the gain arm. Theoretical estimation of laser output energy and pulse width has been carried out by varying input power levels and resonator length to analyse the performance tolerances. The designed system is capable of meeting the objective of generating laser pulses of 10 ns duration and 30 mJ energy @ 10 Hz.

Accelerated Air-coupled Ultrasound Imaging of Wood Using Compressed Sensing

Directory of Open Access Journals (Sweden)

Yiming Fang

2015-12-01

Full Text Available Air-coupled ultrasound has shown excellent sensitivity and specificity for the nondestructive imaging of wood-based material. However, it is time-consuming, due to the high scanning density limited by the Nyquist law. This study investigated the feasibility of applying compressed sensing techniques to air-coupled ultrasound imaging, aiming to reduce the number of scanning lines and then accelerate the imaging. Firstly, an undersampled scanning strategy specified by a random binary matrix was proposed to address the limitation of the compressed sensing framework. The undersampled scanning can be easily implemented, while only minor modification was required for the existing imaging system. Then, discrete cosine transform was selected experimentally as the representation basis. Finally, orthogonal matching pursuit algorithm was utilized to reconstruct the wood images. Experiments on three real air-coupled ultrasound images indicated the potential of the present method to accelerate air-coupled ultrasound imaging of wood. The same quality of ACU images can be obtained with scanning time cut in half.

5.5 W near-diffraction-limited power from resonant leaky-wave coupled phase-locked arrays of quantum cascade lasers

International Nuclear Information System (INIS)

Kirch, J. D.; Chang, C.-C.; Boyle, C.; Mawst, L. J.; Botez, D.; Lindberg, D.; Earles, T.

2015-01-01

Five, 8.36 μm-emitting quantum-cascade lasers (QCLs) have been monolithically phase-locked in the in-phase array mode via resonant leaky-wave coupling. The structure is fabricated by etch and regrowth which provides large index steps (Δn = 0.10) between antiguided-array elements and interelement regions. Such high index contrast photonic-crystal (PC) lasers have more than an order of magnitude higher index contrast than PC-distributed feedback lasers previously used for coherent beam combining in QCLs. Absorption loss to metal layers inserted in the interelement regions provides a wide (∼1.0 μm) range in interelement width over which the resonant in-phase mode is strongly favored to lase. Room-temperature, in-phase-mode operation with ∼2.2 kA/cm 2 threshold-current density is obtained from 105 μm-wide aperture devices. The far-field beam pattern has lobewidths 1.65× diffraction limit (D.L.) and 82% of the light in the main lobe, up to 1.8× threshold. Peak pulsed near-D.L. power of 5.5 W is obtained, with 4.5 W emitted in the main lobe. Means of how to increase the device internal efficiency are discussed

Coherence Phenomena in Coupled Optical Resonators

Science.gov (United States)

Smith, D. D.; Chang, H.

2004-01-01

We predict a variety of photonic coherence phenomena in passive and active coupled ring resonators. Specifically, the effective dispersive and absorptive steady-state response of coupled resonators is derived, and used to determine the conditions for coupled-resonator-induced transparency and absorption, lasing without gain, and cooperative cavity emission. These effects rely on coherent photon trapping, in direct analogy with coherent population trapping phenomena in atomic systems. We also demonstrate that the coupled-mode equations are formally identical to the two-level atom Schrodinger equation in the rotating-wave approximation, and use this result for the analysis of coupled-resonator photon dynamics. Notably, because these effects are predicted directly from coupled-mode theory, they are not unique to atoms, but rather are fundamental to systems of coherently coupled resonators.

Random Sequence for Optimal Low-Power Laser Generated Ultrasound

Science.gov (United States)

Vangi, D.; Virga, A.; Gulino, M. S.

2017-08-01

Low-power laser generated ultrasounds are lately gaining importance in the research world, thanks to the possibility of investigating a mechanical component structural integrity through a non-contact and Non-Destructive Testing (NDT) procedure. The ultrasounds are, however, very low in amplitude, making it necessary to use pre-processing and post-processing operations on the signals to detect them. The cross-correlation technique is used in this work, meaning that a random signal must be used as laser input. For this purpose, a highly random and simple-to-create code called T sequence, capable of enhancing the ultrasound detectability, is introduced (not previously available at the state of the art). Several important parameters which characterize the T sequence can influence the process: the number of pulses Npulses , the pulse duration δ and the distance between pulses dpulses . A Finite Element FE model of a 3 mm steel disk has been initially developed to analytically study the longitudinal ultrasound generation mechanism and the obtainable outputs. Later, experimental tests have shown that the T sequence is highly flexible for ultrasound detection purposes, making it optimal to use high Npulses and δ but low dpulses . In the end, apart from describing all phenomena that arise in the low-power laser generation process, the results of this study are also important for setting up an effective NDT procedure using this technology.

Ultrasound imparted air-recoil resonance (UIAR) method for acoustic power estimation: theory and experiment.

Science.gov (United States)

Kaiplavil, Sreekumar; Rivens, Ian; ter Haar, Gail

2013-07-01

Ultrasound imparted air-recoil resonance (UIAR), a new method for acoustic power estimation, is introduced with emphasis on therapeutic high-intensity focused ultrasound (HIFU) monitoring applications. Advantages of this approach over existing practices include fast response; electrical and magnetic inertness, and hence MRI compatibility; portability; high damage threshold and immunity to vibration and interference; low cost; etc. The angle of incidence should be fixed for accurate measurement. However, the transducer-detector pair can be aligned in any direction with respect to the force of gravity. In this sense, the operation of the device is orientation independent. The acoustic response of a pneumatically coupled pair of Helmholtz resonators, with one of them acting as the sensor head, is used for the estimation of acoustic power. The principle is valid in the case of pulsed/ burst as well as continuous ultrasound exposure, the former being more sensitive and accurate. An electro-acoustic theory has been developed for describing the dynamics of pressure flow and resonance in the system considering various thermo- viscous loss mechanisms. Experimental observations are found to be in agreement with theoretical results. Assuming the window damage threshold (~10 J·mm(-2)) and accuracy of RF power estimation are the upper and lower scale-limiting factors, the performance of the device was examined for an RF power range of 5 mW to 100 W with a HIFU transducer operating at 1.70 MHz, and an average nonlinearity of ~1.5% was observed. The device is also sensitive to sub-milliwatt powers. The frequency response was analyzed at 0.85, 1.70, 2.55, and 3.40 MHz and the results are presented with respective theoretical estimates. Typical response time is in the millisecond regime. Output drift is about 3% for resonant and 5% for nonresonant modes. The principle has been optimized to demonstrate a general-purpose acoustic power meter.

Differential interferometer for measurement of displacement of laser resonator mirrors

Science.gov (United States)

Macúchová, Karolina; Němcová, Šárka; Hošek, Jan

2015-01-01

This paper covers a description and a technique of a possible optical method of mode locking within a laser resonator. The measurement system is a part of instrumentation of laser-based experiment OSQAR at CERN. The OSQAR experiment aims at search of axions, axion-like particles and measuring of ultra-fine vacuum magnetic birefringence. It uses a laser resonator to enhance the coupling constant of hypothetical photon-to-axion conversion. The developed locking-in technique is based on differential interferometry. Signal obtained from the measurement provide crucial information for adaptive control of the locking-in of the resonator in real time. In this paper we propose several optical setups used for measurement and analysis of mutual position of the resonator mirrors. We have set up a differential interferometer under our laboratory conditions. We have done measurements with hemi-spherical cavity resonator detuned with piezo crystals. The measurement was set up in a single plane. Laser light was directed through half-wave retarder to a polarizing beam splitter and then converted to circular polarization by lambda/4 plates. After reflection at the mirrors, the beam is recombined in a beam splitter, sent to analyser and non-polarizing beam splitter and then inspected by two detectors with mutually perpendicular polarizers. The 90 degrees phase shift between the two arms allows precise analysis of a mutual distance change of the mirrors. Because our setup was sufficiently stable, we were able to measure the piezo constant and piezo hysteresis. The final goal is to adapt the first prototype to 23 m resonator and measure the displacement in two planes.

Laser streaming: Turning a laser beam into a flow of liquid.

Science.gov (United States)

Wang, Yanan; Zhang, Qiuhui; Zhu, Zhuan; Lin, Feng; Deng, Jiangdong; Ku, Geng; Dong, Suchuan; Song, Shuo; Alam, Md Kamrul; Liu, Dong; Wang, Zhiming; Bao, Jiming

2017-09-01

Transforming a laser beam into a mass flow has been a challenge both scientifically and technologically. We report the discovery of a new optofluidic principle and demonstrate the generation of a steady-state water flow by a pulsed laser beam through a glass window. To generate a flow or stream in the same path as the refracted laser beam in pure water from an arbitrary spot on the window, we first fill a glass cuvette with an aqueous solution of Au nanoparticles. A flow will emerge from the focused laser spot on the window after the laser is turned on for a few to tens of minutes; the flow remains after the colloidal solution is completely replaced by pure water. Microscopically, this transformation is made possible by an underlying plasmonic nanoparticle-decorated cavity, which is self-fabricated on the glass by nanoparticle-assisted laser etching and exhibits size and shape uniquely tailored to the incident beam profile. Hydrophone signals indicate that the flow is driven via acoustic streaming by a long-lasting ultrasound wave that is resonantly generated by the laser and the cavity through the photoacoustic effect. The principle of this light-driven flow via ultrasound, that is, photoacoustic streaming by coupling photoacoustics to acoustic streaming, is general and can be applied to any liquid, opening up new research and applications in optofluidics as well as traditional photoacoustics and acoustic streaming.

Laser generated ultrasound sources using polymer nanocomposites for high frequency metrology

KAUST Repository

Rajagopal, Srinath

2017-11-22

Accurate characterization of ultrasound fields generated by diagnostic and therapeutic transducers is critical for patient safety. This requires hydrophones calibrated to a traceable standard and currently the upper calibration frequency range available to the user community is limited to a frequency of 40 MHz. However, the increasing use of high frequencies for both imaging and therapy necessitates calibrations to frequencies well beyond this range. For this to be possible, a source of high amplitude, broadband, quasi-planar and stable ultrasound fields is required. This is difficult to achieve using conventional piezoelectric sources, but laser generated ultrasound is a promising technique in this regard. In this study, various polymer-carbon nanotube nanocomposites (PNC) were fabricated and tested for their suitability for such an application by varying the polymer type, carbon nanotubes weight content in the polymer, and PNC thickness. A broadband hydrophone was used to measure the peak pressure and bandwidth of the laser generated ultrasound pulse. Peak-positive pressures of up to 8 MPa and −6dB bandwidths of up to 40 MHz were recorded. There is a nonlinear dependence of the peak pressure on the laser fluence and the bandwidth scales inversely proportionally to the peak pressure. The high-pressure plane waves generated from this preliminary investigation has demonstrated that laser generated ultrasound sources are a promising technique for high frequency calibration of hydrophones.

Resonance Ionization Laser Ion Sources

CERN Document Server

Marsh, B

2013-01-01

The application of the technique of laser resonance ionization to the production of singly charged ions at radioactive ion beam facilities is discussed. The ability to combine high efficiency and element selectivity makes a resonance ionization laser ion source (RILIS) an important component of many radioactive ion beam facilities. At CERN, for example, the RILIS is the most commonly used ion source of the ISOLDE facility, with a yearly operating time of up to 3000 hours. For some isotopes the RILIS can also be used as a fast and sensitive laser spectroscopy tool, provided that the spectral resolution is sufficiently high to reveal the influence of nuclear structure on the atomic spectra. This enables the study of nuclear properties of isotopes with production rates even lower than one ion per second and, in some cases, enables isomer selective ionization. The solutions available for the implementation of resonance laser ionization at radioactive ion beam facilities are summarized. Aspects such as the laser r...

Above-threshold ionization of atoms by resonant XUV laser pulses

Energy Technology Data Exchange (ETDEWEB)

Rodriguez, V D [Departamento de Fisica and IFIBA-CONICET, FCEyN, Universidad de Buenos Aires, 1428 Buenos Aires (Argentina); Arbo, D G [Instituto de AstronomIa y Fisica del Espacio, FCEN-UBA CONICET, CC 67 Suc 28 Buenos Aires (Argentina); Macri, P A, E-mail: vladimir@df.uba.ar [Departamento de Fisica, FCEyN, Instituto de Investigaciones Fisicas de Mar del Plata (IFIMAR), Universidad Nacional de Mar del Plata-CONICET, Funes 3350, 7600 Mar del Plata (Argentina)

2011-06-28

Above-threshold ionization of atoms by XUV short laser pulses with frequencies close to the resonant 1s-2p transition is investigated. We present a theory based on a variational expression using trial wavefunctions for the final and the initial states. For the former we use a Coulomb-Volkov wavefunction, and for the latter a close-coupling solution of the time-dependent Schroedinger equation considering a few bound states. The close-coupling Coulomb-Volkov theory, fully accounting for the important 1s-2p transition, explains the photoelectron spectrum as well as the total ionization cross sections for the resonant case. We also compare the partial wave populations and angular distributions given by the theory with the numerical solutions of the time-dependent Schroedinger equation.

Real-Time Laser Ultrasound Tomography for Profilometry of Solids

Science.gov (United States)

Zarubin, V. P.; Bychkov, A. S.; Karabutov, A. A.; Simonova, V. A.; Kudinov, I. A.; Cherepetskaya, E. B.

2018-01-01

We studied the possibility of applying laser ultrasound tomography for profilometry of solids. The proposed approach provides high spatial resolution and efficiency, as well as profilometry of contaminated objects or objects submerged in liquids. The algorithms for the construction of tomograms and recognition of the profiles of studied objects using the parallel programming technology NDIVIA CUDA are proposed. A prototype of the real-time laser ultrasound profilometer was used to obtain the profiles of solid surfaces of revolution. The proposed method allows the real-time determination of the surface position for cylindrical objects with an approximation accuracy of up to 16 μm.

Quantum oscillation amplification of the ultrasound polarization parameters in tungsten during coupling with the spiral wave

International Nuclear Information System (INIS)

Gudkov, V.V.; Zhevstovskikh, I.V.; Zimbovskaya, N.A.; Okulov, V.I.

1991-01-01

The quantum oscillations are studied of ellipcity, the rotation angle of the ultrasound polarization plane, the velocity and absorption of waves polarized circularly at the 196 MHz frequency in a tungsten single crystal in magnetic field of 30-80 kOe at temperature 1,8 K. The oscillation amplitudes of ellipticity and rotation angle of the ultrasound polarization plane beyond the Doppler-shifted cyclotron resonance are found to vary nonmonotonously with field and to be large enough, so that they are not described by the simple expressions for high fields. The explanation for the oscillation amplification of the polarization parameters is given within the theory involving the ultrasound-spiral wave coupling predicted by Kaner and Skobov. The quantitative comparison in details demonstrates a good agreement in the theory and experimental data and allows to find the numerical values of new parameters characterizing the Fermi surface, electron relaxation frequency, and deformation potential

Development of an optical resonator with high-efficient output coupler for the JAERI far-infrared free-electron laser

International Nuclear Information System (INIS)

Nagai, Ryoji; Hajima, Ryoichi; Nishimori, Nobuyuki; Sawamura, Masaru; Kikuzawa, Nobuhiro; Shizuma, Toshiyuki; Minehara, Eisuke

2001-01-01

An optical resonator with a high-efficient output coupler was developed for the JAERI far-infrared free-electron laser. The optical resonator is symmetrical near-concentric geometry with an insertable scraper output coupler. As a result of the development of the optical resonator, the JAERI-FEL has been successfully, lased with averaged power over 1 kW. Performance of the optical resonator with the output coupler was evaluated at optical wavelength of 22 μm by using an optical mode calculation code. The output coupling and diffractive loss with a dominant eigen-mode of the resonator were calculated using an iterative computation called Fox-Li procedure. An efficiency factor of the optical resonator was introduced for the evaluation of the optical resonator performance. The efficiency factor was derived by the amount of the output coupling and diffractive loss of the optical resonator. It was found that the optical resonator with the insertable scraper coupler was the most suitable to a high-power and high-efficient far-infrared free-electron laser. (author)

Dynamic nonlinear thermal optical effects in coupled ring resonators

Directory of Open Access Journals (Sweden)

Chenguang Huang

2012-09-01

Full Text Available We investigate the dynamic nonlinear thermal optical effects in a photonic system of two coupled ring resonators. A bus waveguide is used to couple light in and out of one of the coupled resonators. Based on the coupling from the bus to the resonator, the coupling between the resonators and the intrinsic loss of each individual resonator, the system transmission spectrum can be classified by three different categories: coupled-resonator-induced absorption, coupled-resonator-induced transparency and over coupled resonance splitting. Dynamic thermal optical effects due to linear absorption have been analyzed for each category as a function of the input power. The heat power in each resonator determines the thermal dynamics in this coupled resonator system. Multiple “shark fins” and power competition between resonators can be foreseen. Also, the nonlinear absorption induced thermal effects have been discussed.

Improving the Selectivity of the ISOLDE Resonance Ionization Laser Ion Source and In-Source Laser Spectroscopy of Polonium

CERN Document Server

Fink, Daniel Andreas; Jochim, Selim

Exotic atomic nuclei far away from stability are fascinating objects to be studied in many scientic elds such as atomic-, nuclear-, and astrophysics. Since these are often short-lived isotopes, it is necessary to couple their production with immediate extraction and delivery to an experiment. This is the purpose of the on-line isotope separator facility, ISOLDE, at CERN. An essential aspect of this laboratory is the Resonance Ionization Laser Ion Source (RILIS) because it provides a fast and highly selective means of ionizing the reaction products. This technique is also a sensitive laser-spectroscopy tool for the development and improvement of electron excitation schemes for the resonant laser photoionization and the study of the nuclear structure or fundamental atomic physics. Each of these aspects of the RILIS applications are subjects of this thesis work: a new device for the suppression of unwanted surface ionized contaminants in RILIS ion beams, known as the Laser Ion Source and Trap (LIST), was impleme...

Laser generated ultrasound sources using polymer nanocomposites for high frequency metrology

KAUST Repository

Rajagopal, Srinath; Sainsbury, Toby; Treeby, Bradley E.; Cox, Ben T.

2017-01-01

amplitude, broadband, quasi-planar and stable ultrasound fields is required. This is difficult to achieve using conventional piezoelectric sources, but laser generated ultrasound is a promising technique in this regard. In this study, various polymer

Quadrature squeezing of a mechanical resonator generated by the electromechanical coupling with two coupled quantum dots

Energy Technology Data Exchange (ETDEWEB)

Yan, Yan [Department of Physics, Huazhong Normal University, Wuhan (China); School of Physics and Optoelectronic Engineering, Yangtze University, Jingzhou (China); Zhu, Jia-pei [Department of Physics, Honghe University, Mengzi (China); Zhao, Shao-ming; Li, Gao-xiang [Department of Physics, Huazhong Normal University, Wuhan (China)

2015-01-01

The quadrature squeezing of a mechanical resonator (MR) coupled with two quantum dots (QDs) through the electromechanical coupling, where the QDs are driven by a strong and two weak laser fields is investigated. By tuning the gate voltage, the electron can be trapped in a quantum pure state. Under certain conditions, the discrepancies between the transition frequency and that of two weak fields are compensated by the phonons induced by the electromechanical coupling of the MR with QDs. In this case, some dissipative processes occur resonantly. The phonons created and (or) annihilated in these dissipative processes are correlated thus leading to the quadrature squeezing of the MR. A squeezed vacuum reservoir for the MR is built up. By tuning the gate voltage to control the energy structure of the QDs, the present squeezing scheme has strong resistance against the dephasing processes of the QDs in low temperature limit. The role of the temperature of the phonon reservoir is to damage squeezing of the MR. (copyright 2014 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

A cyclotron resonance laser accelerator

International Nuclear Information System (INIS)

Sprangle, P.; Tang, C.M.; Vlahos, L.

1983-01-01

A laser acceleration mechanism which utilizes a strong static, almost uniform, magnetic field together with an intense laser pulse is analyzed. The interaction and acceleration mechanism relies on a self resonance effect. Since the laser field is assumed to be diffraction limited, the magnetic field must be spatially varied to maintain resonance. The effective accelerating gradient is shown to scale like 1/√E /SUB b/ , where E /SUB b/ is the electron energy. For a numerical illustration the authors consider a 1 x 10 13 W/cm 2 , CO 2 laser and show that electrons can be accelerated to more than 500 MeV in a distance of 15 m (approximately two Rayleigh lengths)

Bubbling in delay-coupled lasers.

Science.gov (United States)

Flunkert, V; D'Huys, O; Danckaert, J; Fischer, I; Schöll, E

2009-06-01

We theoretically study chaos synchronization of two lasers which are delay coupled via an active or a passive relay. While the lasers are synchronized, their dynamics is identical to a single laser with delayed feedback for a passive relay and identical to two delay-coupled lasers for an active relay. Depending on the coupling parameters the system exhibits bubbling, i.e., noise-induced desynchronization, or on-off intermittency. We associate the desynchronization dynamics in the coherence collapse and low-frequency fluctuation regimes with the transverse instability of some of the compound cavity's antimodes. Finally, we demonstrate how, by using an active relay, bubbling can be suppressed.

Non-Contact Laser Based Ultrasound Evaluation of Canned Foods

Science.gov (United States)

Shelton, David

2005-03-01

Laser-Based Ultrasound detection was used to measure the velocity of compression waves transmitted through canned foods. Condensed broth, canned pasta, and non-condensed soup were evaluated in these experiments. Homodyne adaptive optics resulted in measurements that were more accurate than the traditional heterodyne method, as well as yielding a 10 dB gain in signal to noise. A-Scans measured the velocity of ultrasound sent through the center of the can and were able to distinguish the quantity of food stuff in its path, as well as distinguish between meat and potato. B-Scans investigated the heterogeneity of the sample’s contents. The evaluation of canned foods was completely non-contact and would be suitable for continuous monitoring in production. These results were verified by conducting the same experiments with a contact piezo transducer. Although the contact method yields a higher signal to noise ratio than the non-contact method, Laser-Based Ultrasound was able to detect surface waves the contact transducer could not.

Magnetic Resonance-Guided High-Intensity-Focused Ultrasound for Palliation of Painful Skeletal Metastases: A Pilot Study.

Science.gov (United States)

Chan, Michael; Dennis, Kristopher; Huang, Yuexi; Mougenot, Charles; Chow, Edward; DeAngelis, Carlo; Coccagna, Jennifer; Sahgal, Arjun; Hynynen, Kullervo; Czarnota, Gregory; Chu, William

2017-10-01

Bone is one of the most common sites of metastases, with bone metastases-related pain representing a significant source of morbidity among patients with cancer. Magnetic resonance-guided focused ultrasound is a noninvasive, outpatient modality with the potential for treating painful bone metastases. The aim of this study is to report our initial experience with magnetic resonance-guided focused ultrasound in the treatment of bone metastases and our preliminary analysis of urinary cytokine levels after therapy. This was a single-center pilot study of 10 patients with metastatic cancer to investigate the feasibility of magnetic resonance-guided focused ultrasound for primary pain control in device-accessible skeletal metastases. Treatments were performed on a clinical magnetic resonance-guided focused ultrasound system using a volumetric ablation technique. Primary efficacy was assessed using Brief Pain Inventory scores and morphine equivalent daily dose intake at 3 time points: before, day 14, and day 30 after the magnetic resonance-guided focused ultrasound treatment. Urine cytokines were measured 3 days before treatment and 2 days after the treatment. Of the 10 patients, 8 were followed up 14 days and 6 were followed up 30 days after the treatment. At day 14, 3 patients (37.5%) exhibited partial pain response and 4 patients (50%) exhibited an indeterminate response, and at day 30 after the treatment, 5 patients (83%) exhibited partial pain response. No treatment-related adverse events were recorded. Of the urine cytokines measured, only Transforming growth factor alpha (TGFα) demonstrated an overall decrease, with a trend toward statistical significance ( P = .078). Our study corroborates magnetic resonance-guided focused ultrasound as a feasible and safe modality as a primary, palliative treatment for painful bone metastases and contributes to the limited body of literature using magnetic resonance-guided focused ultrasound for this clinical indication.

A new mode of acoustic NDT via resonant air-coupled emission

Science.gov (United States)

Solodov, Igor; Dillenz, Alexander; Kreutzbruck, Marc

2017-06-01

Resonant modes of non-destructive testing (NDT) which make use of local damage resonance (LDR) have been developed recently and demonstrated a significant increase in efficiency and sensitivity of hybrid inspection techniques by laser vibrometry, ultrasonic thermography, and shearography. In this paper, a new fully acoustic version of resonant NDT is demonstrated for defects in composite materials relevant to automotive and aviation applications. This technique is based on an efficient activation of defect vibrations by using a sonic/ultrasonic wave matched to a fundamental LDR frequency of the defect. On this condition, all points of the faulty area get involved in synchronous out-of-plane vibrations which produce a similar in-phase wave motion in ambient air. This effect of resonant air-coupled emission results in airborne waves emanating from the defect area, which can be received by a commercial microphone (low LDR frequency) or an air-coupled ultrasonic transducer (high frequency LDR). A series of experiments confirm the feasibility of both contact and non-contact versions of the technique for NDT and imaging of simulated and realistic defects (impacts, delaminations, and disbonds) in composites.

Resonant coupling applied to superconducting accelerator structures

International Nuclear Information System (INIS)

Potter, James M.; Krawczyk, Frank L.

2013-01-01

The concept of resonant coupling and the benefits that accrue from its application is well known in the world of room temperature coupled cavity linacs. Design studies show that it can be applied successfully between sections of conventional elliptical superconducting coupled cavity accelerator structures and internally to structures with spoked cavity resonators. The coupling mechanisms can be designed without creating problems with high field regions or multipactoring. The application of resonant coupling to superconducting accelerators eliminates the need for complex cryogenic mechanical tuners and reduces the time needed to bring a superconducting accelerator into operation.

Wavelength-controlled external-cavity laser with a silicon photonic crystal resonant reflector

Science.gov (United States)

Gonzalez-Fernandez, A. A.; Liles, Alexandros A.; Persheyev, Saydulla; Debnath, Kapil; O'Faolain, Liam

2016-03-01

We report the experimental demonstration of an alternative design of external-cavity hybrid lasers consisting of a III-V Semiconductor Optical Amplifier with fiber reflector and a Photonic Crystal (PhC) based resonant reflector on SOI. The Silicon reflector comprises a polymer (SU8) bus waveguide vertically coupled to a PhC cavity and provides a wavelength-selective optical feedback to the laser cavity. This device exhibits milliwatt-level output power and sidemode suppression ratio of more than 25 dB.

Tunable Landau-Zener transitions using continuous- and chirped-pulse-laser couplings

Science.gov (United States)

Sarreshtedari, Farrokh; Hosseini, Mehdi

2017-03-01

The laser coupled Landau-Zener avoided crossing has been investigated with an aim towards obtaining the laser source parameters for precise controlling of the state dynamics in a two-level quantum system. The conventional Landau-Zener equation is modified for including the interaction of the system with a laser field during a bias energy sweep and the obtained Hamiltonian is numerically solved for the investigation of the two-state occupation probabilities. We have shown that in the Landau-Zener process, using an additional laser source with controlled amplitude, frequency, and phase, the system dynamics could be arbitrarily engineered. This is while, by synchronous frequency sweeping of a chirped-pulse laser, the system could be guided into a resonance condition, which again gives the remarkable possibility for precise tuning and controlling of the quantum system dynamics.

Low power laser generated ultrasound: Signal processing for time domain data acquisition

International Nuclear Information System (INIS)

Cleary, A; Thursby, G; McKee, C; Armstrong, I; Culshaw, B; Veres, I; Pierce, S G

2011-01-01

The use of low power modulated laser diode systems has previously been established as a suitable method for non-destructive laser generation of ultrasound. Using a quasi-continuous optical excitation amplified by an erbium-doped fibre amplifier (EDFA) allows flexible generation of ultrasonic waves, offering control of further parameters such as the frequency content or signal shape. In addition, pseudo-random binary sequences (PRBS) can be used to improve the detected impulse response. Here we compare two sequences, the m-sequence and the Golay code, and discuss the advantages and practical limits of their application with laser diode based optical excitation of ultrasound.

Dissimilar trend of nonlinearity in ultrasound transducers and systems at resonance and non-resonance frequencies

DEFF Research Database (Denmark)

Ghasemi, Negareh; Zare, Firuz; Davari, Pooya

2017-01-01

Several factors can affect performance of an ultrasound system such as quality of excitation signal and ultrasound transducer behaviour. Nonlinearity of piezoelectric ultrasound transducers is a key determinant in designing a proper driving power supply. Although, the nonlinearity of piezoelectric...... was excited at different frequencies. Different excitation signals were generated using a linear power amplifier and a multilevel converter within a range of 30–200 V. Empirical relation was developed to express the resistance of the piezoelectric transducer as a nonlinear function of both excitation voltage...... and resonance frequency. The impedance measurements revealed that at higher voltage ranges, the piezoelectric transducer can be easily saturated. Also, it was shown that for the developed ultrasound system composed of two transducers (one transmitter and one receiver), the output voltage measured across...

Laser magnetic resonance spectroscopy

International Nuclear Information System (INIS)

Ferrari, C.A.

1985-01-01

The technique of laser resonance magnetic resonance allows one to study the high-resolution spectroscopy of transient paramagnetic species, viz, atoms, radicals, and molecular ions. This article is a brief exposition of the method, describing the principles, instrumentation and applicability of the IR and FIR-LMR and shows results of HF + . (Author) [pt

Monolithic optofluidic ring resonator lasers created by femtosecond laser nanofabrication.

Science.gov (United States)

Chandrahalim, Hengky; Chen, Qiushu; Said, Ali A; Dugan, Mark; Fan, Xudong

2015-05-21

We designed, fabricated, and characterized a monolithically integrated optofluidic ring resonator laser that is mechanically, thermally, and chemically robust. The entire device, including the ring resonator channel and sample delivery microfluidics, was created in a block of fused-silica glass using a 3-dimensional femtosecond laser writing process. The gain medium, composed of Rhodamine 6G (R6G) dissolved in quinoline, was flowed through the ring resonator. Lasing was achieved at a pump threshold of approximately 15 μJ mm(-2). Detailed analysis shows that the Q-factor of the optofluidic ring resonator is 3.3 × 10(4), which is limited by both solvent absorption and scattering loss. In particular, a Q-factor resulting from the scattering loss can be as high as 4.2 × 10(4), suggesting the feasibility of using a femtosecond laser to create high quality optical cavities.

Imaging of Groin Pain: Magnetic Resonance and Ultrasound Imaging Features.

Science.gov (United States)

Lee, Susan C; Endo, Yoshimi; Potter, Hollis G

Evaluation of groin pain in athletes may be challenging as pain is typically poorly localized and the pubic symphyseal region comprises closely approximated tendons and muscles. As such, magnetic resonance imaging (MRI) and ultrasound (US) may help determine the etiology of groin pain. A PubMed search was performed using the following search terms: ultrasound, magnetic resonance imaging, sports hernia, athletic pubalgia, and groin pain. Date restrictions were not placed on the literature search. Clinical review. Level 4. MRI is sensitive in diagnosing pathology in groin pain. Not only can MRI be used to image rectus abdominis/adductor longus aponeurosis and pubic bone pathology, but it can also evaluate other pathology within the hip and pelvis. MRI is especially helpful when groin pain is poorly localized. Real-time capability makes ultrasound useful in evaluating the pubic symphyseal region, as it can be used for evaluation and treatment. MRI and US are valuable in diagnosing pathology in athletes with groin pain, with the added utility of treatment using US-guided intervention. Strength-of Recommendation Taxonomy: C.

High-frequency ultrasound evaluation of cellulite treated with the 1064 nm Nd:YAG laser.

Science.gov (United States)

Bousquet-Rouaud, Regine; Bazan, Marie; Chaintreuil, Jean; Echague, Agustina Vila

2009-03-01

To investigate non-invasive laser treatment for cellulite using the 1064 nm Nd:YAG laser and to correlate clinical results with high-frequency skin ultrasound images. Twelve individuals of normal weight were treated on either the left or right posterior side of the thigh with the following parameters: fluence 30 J/cm, 18 mm spot size and dynamic cooling device pulse duration of 30 ms. Three treatments were performed at intervals of 3-4 weeks, and followed-up 1 and 3 months after the last session. Photographs and ultrasound imaging were assessed before each session. The 1064 nm Nd:YAG laser resulted in a tightening of the skin and an improvement in cellulite. No side effects were reported. High-resolution ultrasound imaging showed a significant improvement in dermis density and a reduction of dermis thickness. The method is described in detail in Appendix 1. Infra-red lasers may constitute a safe and effective treatment for cellulite and high-frequency ultrasound imaging provides a quantitative and objective measurement of the treatment efficacy.

Effect of self-focusing on resonant third harmonic generation of laser in a rippled density plasma

International Nuclear Information System (INIS)

Kaur, Sukhdeep; Sharma, A. K.; Yadav, Sushila

2010-01-01

Resonant third harmonic generation by a Gaussian laser beam in a rippled density plasma is studied. The laser ponderomotive force induces second harmonic longitudinal velocity on electrons that couples with the static density ripple to produce a density perturbation at 2ω,2k+q, where ω and k are the frequency and wave number of the laser and q is the ripple wave number of the laser. This density perturbation beats with electron oscillatory velocity at ω,k-vector to produce a nonlinear current driving the third harmonic generation. In the regime of quadratic nonlinearity, the self-focusing of the laser enhances the third harmonic power. However, at higher intensity, plasma density is significantly reduced on the axis, detuning the third harmonic resonance and weakening the harmonic yield. Self-focusing causes enhancement in the efficiency of harmonic generation.

Clinically low-risk prostate cancer: evaluation with transrectal doppler ultrasound and functional magnetic resonance imaging

Directory of Open Access Journals (Sweden)

Maria Inês Novis

2011-01-01

Full Text Available OBJECTIVES: To evaluate transrectal ultrasound, amplitude Doppler ultrasound, conventional T2-weighted magnetic resonance imaging, spectroscopy and dynamic contrast-enhanced magnetic resonance imaging in localizing and locally staging low-risk prostate cancer. INTRODUCTION: Prostate cancer has been diagnosed at earlier stages and the most accepted classification for low-risk prostate cancer is based on clinical stage T1c or T2a, Gleason score <6, and prostate-specific antigen (PSA <10 ng/ml. METHODS: From 2005 to 2006, magnetic resonance imaging was performed in 42 patients, and transrectal ultrasound in 26 of these patients. Seven patients were excluded from the study. Mean patient age was 64.94 years and mean serum PSA was 6.05 ng/ml. The examinations were analyzed for tumor identification and location in prostate sextants, detection of extracapsular extension, and seminal vesicle invasion, using surgical pathology findings as the gold standard. RESULTS: Sixteen patients (45.7% had pathologically proven organ-confined disease, 11 (31.4% had positive surgical margin, 8 (28.9% had extracapsular extension, and 3 (8.6% presented with extracapsular extension and seminal vesicle invasion. Sensitivity, specificity, positive predictive value (PPV, negative predictive value (NPV and accuracy values for localizing low-risk prostate cancer were 53.1%, 48.3%, 63.4%, 37.8% and 51.3% for transrectal ultrasound; 70.4%, 36.2%, 65.1%, 42.0% and 57.7% for amplitude Doppler ultrasound; 71.5%, 58.9%, 76.6%, 52.4% and 67.1% for magnetic resonance imaging; 70.4%, 58.7%, 78.4%, 48.2% and 66.7% for magnetic resonance spectroscopy; 67.2%, 65.7%, 79.3%, 50.6% and 66.7% for dynamic contrast-enhanced magnetic resonance imaging, respectively. Sensitivity, specificity, PPV, NPV and accuracy values for detecting extracapsular extension were 33.3%, 92%, 14.3%, 97.2% and 89.7% for transrectal ultrasound and 50.0%, 77.6%, 13.7%, 95.6% and 75.7% for magnetic resonance imaging

Lens Coupled Quantum Cascade Laser

Science.gov (United States)

Hu, Qing (Inventor); Lee, Alan Wei Min (Inventor)

2013-01-01

Terahertz quantum cascade (QC) devices are disclosed that can operate, e.g., in a range of about 1 THz to about 10 THz. In some embodiments, QC lasers are disclosed in which an optical element (e.g., a lens) is coupled to an output facet of the laser's active region to enhance coupling of the lasing radiation from the active region to an external environment. In other embodiments, terahertz amplifier and tunable terahertz QC lasers are disclosed.

Stimulated resonance Raman spectroscopy: An alternative to laser-rf double resonance for ion spectroscopy

International Nuclear Information System (INIS)

Young, L.; Dinneen, T.; Mansour, N.B.

1988-01-01

Stimulated resonance Raman spectroscopy is presented as an alternative to laser-rf double resonance for obtaining high-precision measurements in ion beams. By use of a single-phase modulated laser beam to derive the two required fields, the laser--ion-beam alignment is significantly simplified. In addition, this method is especially useful in the low-frequency regime where the laser-rf double-resonance method encounters difficulties due to modifications of the ion-beam velocity distribution. These modifications, which result from interaction with the traveling rf wave used to induce magnetic dipole transitions, are observed and quantitatively modeled

Silicon photonic micro-ring resonators to sense strain and ultrasound

NARCIS (Netherlands)

Westerveld, W.J.

2014-01-01

We demonstrated that photonic micro-ring resonators can be used in micro-machined ultrasound microphones. This might cause a breakthrough in array transducers for ultrasonography; first because optical multiplexing allows array interrogation via one optical fiber and second because the

Study of distributed fiber-optic laser-ultrasound generation based on ghost-mode of tilted fiber Bragg gratings

Science.gov (United States)

Tian, Jiajun; Zhang, Qi; Han, Ming

2013-05-01

Fiber-optic ultrasonic transducers are an important component of an active ultrasonic testing system for structural health monitoring. Fiber-optic transducers have several advantages such as small size, light weight, and immunity to electromagnetic interference that make them much more attractive than the current available piezoelectric transducers, especially as embedded and permanent transducers in active ultrasonic testing for structural health monitoring. In this paper, a distributed fiber-optic laser-ultrasound generation based on the ghost-mode of tilted fiber Bragg gratings is studied. The influences of the laser power and laser pulse duration on the laser-ultrasound generation are investigated. The results of this paper are helpful to understand the working principle of this laser-ultrasound method and improve the ultrasonic generation efficiency.

Superthin resonator dye laser with THz intermode frequency separation

International Nuclear Information System (INIS)

Rudych, P D; Surovtsev, N V

2014-01-01

Two-color laser irradiation is considered an effective way to pump THz excitations for numerous scientific and applied goals. We present a design for convenient laser source with THz intermode frequency separation. The setup is based on dye laser with superthin resonator pumped by a subnanosecond pulse laser. It was proven that the superthin resonator dye laser is useful, possesses high stability and high energy conversion, and generates narrow laser modes. The ability of this laser to pump CARS processes for THz vibrations is demonstrated. (letter)

Ultrasound versus high field magnetic resonance imaging in rheumatoid arthritis

DEFF Research Database (Denmark)

Tan, York Kiat; Østergaard, Mikkel; Bird, Paul

2014-01-01

Over the past decade there have been significant advances in the field of musculoskeletal imaging, especially in the application of ultrasound (US) and magnetic resonance imaging (MRI) to the management of rheumatoid arthritis (RA). Both modalities offer significant advantages over the previous...

A study of pipe flow rate measurement using air-coupled ultrasound

International Nuclear Information System (INIS)

Tsukada, Keisuke; Tsuzuki, Nobuyoshi; Kikura, Hiroshige

2013-01-01

A non-contact flow meter employing air-coupled ultrasound is developed in this research. Ultrasonic flow meter is applied to the higher accuracy flow rate measurement, compared with pressure difference flow meter. However, ultrasonic flow meter has difficulty to measure in severe conditions such as in the condition of high temperature, high pressure condition, and radioactive materials in fluid. Especially, in high temperature condition, piezoelectric device in ultrasonic sensors lose the piezoelectricity, and it becomes difficult to transmit or detect ultrasound. Thus, in this research, ultrasonic sensors are fixed in the air. Ultrasonic sensors transmit and detect ultrasound through air, and measure the flow rate in the pipe. However, most of ultrasound is refracted and reflected at the boundaries between air and the pipe. And detected signals are weak. To increase the signal level, we developed focusing ultrasonic sensors that was optimized for the pipe flow measurement. And employing these focusing sensors the flow rate measurement has been done in order to evaluate the air-coupled ultrasonic flow meter by the ultrasonic beam focusing technique. (author)

Phase locking of optically coupled lasers

International Nuclear Information System (INIS)

Glova, A F

2003-01-01

A review of studies of the properties of radiation from optically coupled lasers is presented. The methods for phase locking the fields in optically coupled lasers of different types are considered and the methods for supermode selection and correction of the radiation pattern are discussed. (review)

Laser of optical fiber composed by two coupled cavities: application as optical fiber sensor

International Nuclear Information System (INIS)

Vazquez S, R.A.; Kuzin, E.A.; Ibarra E, B.; May A, M.; Shlyagin, M.; Marquez B, I.

2004-01-01

We show an optical fiber laser sensor which consist of two cavities coupled and three fiber Bragg gratings. We used one Bragg grating (called reference) and two Bragg gratings (called sensors), which have the lower reflection wavelength. The reference grating with the two sensors grating make two cavities: first one is the internal cavity which has 4230 m of length and the another one is the external cavity which has 4277 m of length. Measuring the laser beating frequency for a resonance cavity and moving the frequency peaks when the another cavity is put in resonance, we prove that the arrangement can be used as a two points sensor for determining the difference of temperature or stress between these two points. (Author)

Optical fiber sensor for the detection of laser-generated ultrasound in arterial tissues

Science.gov (United States)

Beard, Paul C.; Mills, Timothy N.

1995-02-01

Theoretical and experimental aspects of an extrinsic Fabry-Perot optical fiber ultrasound sensor for use in a photoacoustic-guided laser angioplasty system are described. The sensor has been characterized using laser generated thermoelastic waves as a source of wideband ultrasound. A system sensitivity of 25 mV/MPa and an acoustic noise floor of 2 Pa/Hz1/2 are reported using a transparent polymer film as the sensing element. The system demonstrates the required bandwidth for sensing thermoelastic waves containing frequency components up to 20 MHz.

Multiple-state Feshbach resonances mediated by high-order couplings

International Nuclear Information System (INIS)

Hemming, Christopher J.; Krems, Roman V.

2008-01-01

We present a study of multistate Feshbach resonances mediated by high-order couplings. Our analysis focuses on a system with one open scattering state and multiple bound states. The scattering state is coupled to one off-resonant bound state and multiple Feshbach resonances are induced by a sequence of indirect couplings between the closed channels. We derive a general recursive expression that can be used to fit the experimental data on multistate Feshbach resonances involving one continuum state and several bound states and present numerical solutions for several model systems. Our results elucidate general features of multistate Feshbach resonances induced by high-order couplings and suggest mechanisms for controlling collisions of ultracold atoms and molecules with external fields

Terahertz Quantum Cascade Laser With Efficient Coupling and Beam Profile

Science.gov (United States)

Chattopadhyay, Goutam; Kawamura, Jonathan H.; Lin, Robert H.; Williams, Benjamin

2012-01-01

Quantum cascade lasers (QCLs) are unipolar semiconductor lasers, where the wavelength of emitted radiation is determined by the engineering of quantum states within the conduction band in coupled multiple-quantum-well heterostructures to have the desired energy separation. The recent development of terahertz QCLs has provided a new generation of solid-state sources for radiation in the terahertz frequency range. Terahertz QCLs have been demonstrated from 0.84 to 5.0 THz both in pulsed mode and continuous wave mode (CW mode). The approach employs a resonant-phonon depopulation concept. The metal-metal (MM) waveguide fabrication is performed using Cu-Cu thermo-compression bonding to bond the GaAs/AlGaAs epitaxial layer to a GaAs receptor wafer.

Evaluation of Air Coupled Ultrasound for Composite Aerospace Structure

Science.gov (United States)

Tat, H.; Georgeson, G.; Bossi, R.

2009-03-01

Non-contact air coupled ultrasound suffers from the high acoustic impedance mismatch characteristics of air to solid interfaces. Advances in transducer technology, particularly MEMS, have improved the acoustic impedance match at the transmission stage and the signal to noise at the reception stage. Comparisons of through transmission (TTU) scanning of laminate and honeycomb test samples using conventional piezoelectric air coupled transducers, new MEMS air coupled transducers, and standard water coupled inspections have been performed to assess the capability. An additional issue for air coupled UT inspection is the need for a lean implementation for both manufacturing and in-service operations. Concepts and applications utilizing magnetic coupling of transducers have been developed that allows air coupled inspection operations in compact low cost configurations.

Detection of a Surface-Breaking Crack by Using the Surface Wave of a Laser Ultrasound

International Nuclear Information System (INIS)

Park, Seung-Kyu; Baik, Sung-Hoon; Jung, Hyun-Kyu; Joo, Young-Sang; Cha, Hyung-Ki; Kang, Young-June

2006-01-01

A laser ultrasonic system is a non-contact inspection device with a high spatial resolution and a wide-band spectrum. Also it provides absolute measurements of the moving distance and can be applied to the hard-to access locations with curved or rough surfaces like a nuclear power plant. Several laser ultrasonic techniques are applied for the detection of micro cracks in a nuclear power plant. Also, laser ultrasonic techniques are used to measure the grain size of materials and to detect cracks in railroads and aircrafts. Though the laser ultrasonic inspection system is widely applicable, it is comparatively expensive and it provides a low signal-to-noise ratio when compared to the conventional piezoelectric transducers. Many studies have been carried out to improve the system performance. One of the widely used measurement devices of a ultrasound is the Confocal Fabry-Perot Interferometer(CFPI) with a dynamic stabilizer. The dynamic stabilizer improves the stability of the CFPI by adaptively maintaining the optimum working status at the measuring time of the CFPI. In this paper, we have investigated the detection methods of the depth of a surface-breaking crack by using the surface wave of a laser ultrasound. We have fabricated a laser ultrasonic inspection system on an optical table by using a pulse laser, a CFPI with a dynamic stabilizer and a computer. The computer acquires the laser ultrasound by using a high speed A/D converter with a sampling rate of 1000 MHz. The dynamic stabilizer stabilizes the CFPI by adaptively maintaining it at an optimum status when the laser ultrasound is generated. The computer processes the ultrasonic signal in real time to extract the depth information of a surface-breaking crack. We extracted the depth information from the peak-to-valley values in the time domain and also from the center frequencies of the spectrum in the frequency domain

General expressions and physical origin of the coupling coefficient of arbitrary tuned coupled electromagnetic resonators

Energy Technology Data Exchange (ETDEWEB)

Elnaggar, Sameh Y. [School of Engineering and Information Technology, University of New South Wales, Canberra (Australia); Tervo, Richard J. [Department of Electrical and Computer Engineering, University of New Brunswick, Fredericton, NB, E3B 5A3 Canada (Canada); Mattar, Saba M., E-mail: mattar@unb.ca [Chemistry Department, University of New Brunswick, Fredericton, NB, E3B 5A3 Canada (Canada)

2015-11-21

The theory and operation of various devices and systems, such as wireless power transfer via magnetic resonant coupling, magneto-inductive wave devices, magnetic resonance spectroscopy probes, and metamaterials can rely on coupled tuned resonators. The coupling strength is usually expressed in terms of the coupling coefficient κ, which can have electrical κ{sub E} and/or magnetic κ{sub M} components. In the current article, general expressions of κ are derived. The relation between the complex Poynting equation in its microscopic form and κ is made and discussed in detail. It is shown that κ can be expressed in terms of the interaction energy between the resonators' modes. It thus provides a general form that combines the magnetic and electric components of κ. The expressions make it possible to estimate the frequencies and fields of the coupled modes for arbitrarily oriented and spaced resonators. Thus, enabling the calculation of system specific parameters such as the transfer efficiency of wireless power transfer systems, resonator efficiency for electron spin resonance probes, and dispersion relations of magneto-inductive and stereo-metamaterials structures.

General expressions and physical origin of the coupling coefficient of arbitrary tuned coupled electromagnetic resonators

International Nuclear Information System (INIS)

Elnaggar, Sameh Y.; Tervo, Richard J.; Mattar, Saba M.

2015-01-01

The theory and operation of various devices and systems, such as wireless power transfer via magnetic resonant coupling, magneto-inductive wave devices, magnetic resonance spectroscopy probes, and metamaterials can rely on coupled tuned resonators. The coupling strength is usually expressed in terms of the coupling coefficient κ, which can have electrical κ E and/or magnetic κ M components. In the current article, general expressions of κ are derived. The relation between the complex Poynting equation in its microscopic form and κ is made and discussed in detail. It is shown that κ can be expressed in terms of the interaction energy between the resonators' modes. It thus provides a general form that combines the magnetic and electric components of κ. The expressions make it possible to estimate the frequencies and fields of the coupled modes for arbitrarily oriented and spaced resonators. Thus, enabling the calculation of system specific parameters such as the transfer efficiency of wireless power transfer systems, resonator efficiency for electron spin resonance probes, and dispersion relations of magneto-inductive and stereo-metamaterials structures

Integrating out resonances in strongly-coupled electroweak scenarios

Directory of Open Access Journals (Sweden)

Rosell Ignasi

2017-01-01

Full Text Available Accepting that there is a mass gap above the electroweak scale, the Electroweak Effective Theory (EWET is an appropriate tool to describe this situation. Since the EWET couplings contain information on the unknown high-energy dynamics, we consider a generic strongly-coupled scenario of electroweak symmetry breaking, where the known particle fields are coupled to heavier states. Then, and by integrating out these heavy fields, we study the tracks of the lightest resonances into the couplings. The determination of the low-energy couplings (LECs in terms of resonance parameters can be made more precise by considering a proper short-distance behaviour on the Lagrangian with heavy states, since the number of resonance couplings is then reduced. Notice that we adopt a generic non-linear realization of the electroweak symmetry breaking with a singlet Higgs.

Comparative study of ultrasound imaging, computed tomography and magnetic resonance imaging in gynecology

International Nuclear Information System (INIS)

Ishii, Kenji; Kobayashi, Hisaaki; Hoshihara, Takayuki; Kobayashi, Mitsunao; Suda, Yoshio; Takenaka, Eiichi; Sasa, Hidenori.

1989-01-01

We studied 18 patients who were operated at the National Defense Medical College Hospital and confirmed by pathological diagnosis. We compared ultrasound imaging, computed tomography (CT) and magnetic resonance imaging (MRI) of the patients. MRI was useful to diagnose enlargement of the uterine cavity and a small amount of ascites and to understand orientation of the pelvic organs. Ultrasound imaging is the most useful examination to diagnose gynecological diseases. But when it is difficult to diagnose by ultrasound imaging alone, we should employ either CT or MRI, or preferably both. (author)

Multipoint fiber-optic laser-ultrasonic actuator based on fiber core-opened tapers.

Science.gov (United States)

Tian, Jiajun; Dong, Xiaolong; Gao, Shimin; Yao, Yong

2017-11-27

In this study, a novel fiber-optic, multipoint, laser-ultrasonic actuator based on fiber core-opened tapers (COTs) is proposed and demonstrated. The COTs were fabricated by splicing single-mode fibers using a standard fiber splicer. A COT can effectively couple part of a core mode into cladding modes, and the coupling ratio can be controlled by adjusting the taper length. Such characteristics are used to obtain a multipoint, laser-ultrasonic actuator with balanced signal strength by reasonably controlling the taper lengths of the COTs. As a prototype, we constructed an actuator that generated ultrasound at four points with a balanced ultrasonic strength by connecting four COTs with coupling ratios of 24.5%, 33.01%, 49.51%, and 87.8% in a fiber link. This simple-to-fabricate, multipoint, laser-ultrasonic actuator with balanced ultrasound signal strength has potential applications in fiber-optic ultrasound testing technology.

Laser-enhanced cavitation during high intensity focused ultrasound: An in vivo study

OpenAIRE

Cui, Huizhong; Zhang, Ti; Yang, Xinmai

2013-01-01

Laser-enhanced cavitation during high intensity focused ultrasound (HIFU) was studied in vivo using a small animal model. Laser light was employed to illuminate the sample concurrently with HIFU radiation. The resulting cavitation was detected with a passive cavitation detector. The in vivo measurements were made under different combinations of HIFU treatment depths, laser wavelengths, and HIFU durations. The results demonstrated that concurrent light illumination during HIFU has the potentia...

Laser cooling at resonance

Science.gov (United States)

Yudkin, Yaakov; Khaykovich, Lev

2018-05-01

We show experimentally that three-dimensional laser cooling of lithium atoms on the D2 line is possible when the laser light is tuned exactly to resonance with the dominant atomic transition. Qualitatively, it can be understood by applying simple Doppler cooling arguments to the specific hyperfine structure of the excited state of lithium atoms, which is both dense and inverted. However, to build a quantitative theory, we must resolve to a full model which takes into account both the entire atomic structure of all 24 Zeeman sublevels and the laser light polarization. Moreover, by means of Monte Carlo simulations, we show that coherent processes play an important role in showing consistency between the theory and the experimental results.

Waveguide-loaded silica fibers for coupling to high-index micro-resonators

Science.gov (United States)

Latawiec, P.; Burek, M. J.; Venkataraman, V.; Lončar, M.

2016-01-01

Tapered silica fibers are often used to rapidly probe the optical properties of micro-resonators. However, their low refractive index precludes phase-matching when coupling to high-index micro-resonators, reducing efficiency. Here, we demonstrate efficient optical coupling from tapered fibers to high-index micro-resonators by loading the fibers with an ancillary adiabatic waveguide-coupler fabricated via angled-etching. We demonstrate greatly enhanced coupling to a silicon multimode micro-resonator when compared to coupling via the bare fiber only. Signatures of resonator optical bistability are observed at high powers. This scheme can be applied to resonators of any size and material, increasing the functional scope of fiber coupling.

Opto-mechanical design of vacuum laser resonator for the OSQAR experiment

Science.gov (United States)

Hošek, Jan; Macúchová, Karolina; Nemcová, Šárka; Kunc, Štěpán.; Šulc, Miroslav

2015-01-01

This paper gives short overview of laser-based experiment OSQAR at CERN which is focused on search of axions and axion-like particles. The OSQAR experiment uses two experimental methods for axion search - measurement of the ultra-fine vacuum magnetic birefringence and a method based on the "Light shining through the wall" experiment. Because both experimental methods have reached its attainable limits of sensitivity we have focused on designing a vacuum laser resonator. The resonator will increase the number of convertible photons and their endurance time within the magnetic field. This paper presents an opto-mechanical design of a two component transportable vacuum laser resonator. Developed optical resonator mechanical design allows to be used as a 0.8 meter long prototype laser resonator for laboratory testing and after transportation and replacement of the mirrors it can be mounted on the LHC magnet in CERN to form a 20 meter long vacuum laser resonator.

Prospective study of ultrasound with perflutrene contrast compared to magnetic resonance imaging in the diagnosis of hepatic hemangiomas

Directory of Open Access Journals (Sweden)

Joel Schmillevitch

2011-06-01

Full Text Available CONTEXT:The incidence of hepatic hemangiomas ranges from 0.4% to 20% in the general population. Conventional ultrasound is usually the first diagnostic method to identify these hemangiomas, typically as an incidental finding. Ultrasonography with second generation contrast materials is being used in various areas of hepatology, yielding similar results to those obtained with computerized tomography and magnetic resonance imaging in the diagnosis of hepatic hemangiomas. OBJECTIVE: To evaluate the agreement between ultrasound with perflutrene contrast and magnetic resonance imaging in the diagnosis of hepatic hemangiomas. METHODS: A total of 37 patients were prospectively examined between January 2006 and August 2008. A total of 57 hepatic nodules were documented in this group as incidental findings on routine ultrasound exams. The 37 patients were administered perflutrene contrast without adverse reactions, and were all submitted to magnetic resonance exams. RESULTS: Conventional ultrasound identified 15 patients with nodules typical of hemangiomas and 22 patients with other nodules. In 35 patients, the contrast characteristics were consistent with hepatic hemangiomas. CONCLUSION: Agreement between the data obtained from ultrasound with contrast and magnetic resonance was 94.5%. In discordant cases, the magnetic resonance diagnosis prevailed. In the case which presented indeterminate findings on contrast ultrasonography, magnetic resonance was repeated after 3 months, confirming the diagnosis of a hepatic hemangioma. A biopsy was performed on the suspected malignant nodule which also confirmed the presence of a hepatic hemangioma. Ultrasonography with contrast has the advantages of being more accessible to the public at large and lower cost than magnetic resonance. The results of our study highlight the need for a new protocol in hepatic nodules incidentally identified on conventional ultrasonography. In the case of typical hemangiomas

Single-mode Brillouin fiber laser passively stabilized at resonance frequency with self-injection locked pump laser

International Nuclear Information System (INIS)

Spirin, V V; Lopez-Mercado, C A; Megret, P; Fotiadi, A A

2012-01-01

We demonstrate a single-mode Brillouin fiber ring laser, which is passively stabilized at pump resonance frequency by using self-injection locking of semiconductor pump laser. Resonance condition for Stokes radiation is achieved by length fitting of Brillouin laser cavity. The laser generate single-frequency Stokes wave with linewidth less than 0.5 kHz using approximately 17-m length cavity

Wave energy extraction by coupled resonant absorbers.

Science.gov (United States)

Evans, D V; Porter, R

2012-01-28

In this article, a range of problems and theories will be introduced that will build towards a new wave energy converter (WEC) concept, with the acronym 'ROTA' standing for resonant over-topping absorber. First, classical results for wave power absorption for WECs constrained to operate in a single degree of freedom will be reviewed and the role of resonance in their operation highlighted. Emphasis will then be placed on how the introduction of further resonances can improve power take-off characteristics by extending the range of frequencies over which the efficiency is close to a theoretical maximum. Methods for doing this in different types of WECs will be demonstrated. Coupled resonant absorbers achieve this by connecting a WEC device equipped with its own resonance (determined from a hydrodynamic analysis) to a new system having separate mass/spring/damper characteristics. It is shown that a coupled resonant effect can be realized by inserting a water tank into a WEC, and this idea forms the basis of the ROTA device. In essence, the idea is to exploit the coupling between the natural sloshing frequencies of the water in the internal tank and the natural resonance of a submerged buoyant circular cylinder device that is tethered to the sea floor, allowing a rotary motion about its axis of attachment.

Doppler ultrasound and magnetic resonance for evaluation of patients treated surgically for aortic coarctation

International Nuclear Information System (INIS)

Canteli, B.; Saez, F.; Garcia, F.; Cabrera, A.; Galdeano, J.M.; Rodriguez, O.

1994-01-01

Doppler ultrasound and magnetic resonance were performed in a series of 39 patients who had been treated surgically for aortic coarctation. The purpose was to assess the different Doppler gradients, comparing the findings with morphological data disclosed by magnetic resonance. The aortic caliber in the operative field was pathological in 7 patients (ratio between the caliber at the level of the lesion and that of descending aorta of less than 0.7). When the patients were considered as a group. Doppler ultrasound did not show satisfactory sensitivity (29%-43%), specificity (74%) or positive predictive value (17%-23%). Only the negative predictive value (85%-88%) presented more favorable results. When the Subgroup of patients without associated cardiac abnormalities or collateral circulation was studied alone, the following results were found: sensitivity, 100%; specificity, 81%-90%, positive predictive value, 33%-50%, negative predictive value, 100%, similar to those reported in the literature. Thus, we consider that Doppler ultrasound is a harmless and low cost diagnostic method that is highly suitable for follow-up of these patients, within certain limits. Magnetic resonance is the method of choice for the noninvasive assessment of aortic morphology. (Author)

Visible high power fiber coupled diode lasers

Science.gov (United States)

Köhler, Bernd; Drovs, Simon; Stoiber, Michael; Dürsch, Sascha; Kissel, Heiko; Könning, Tobias; Biesenbach, Jens; König, Harald; Lell, Alfred; Stojetz, Bernhard; Löffler, Andreas; Strauß, Uwe

2018-02-01

In this paper we report on further development of fiber coupled high-power diode lasers in the visible spectral range. New visible laser modules presented in this paper include the use of multi single emitter arrays @ 450 nm leading to a 120 W fiber coupled unit with a beam quality of 44 mm x mrad, as well as very compact modules with multi-W output power from 405 nm to 640 nm. However, as these lasers are based on single emitters, power scaling quickly leads to bulky laser units with a lot of optical components to be aligned. We also report on a new approach based on 450 nm diode laser bars, which dramatically reduces size and alignment effort. These activities were performed within the German government-funded project "BlauLas": a maximum output power of 80 W per bar has been demonstrated @ 450 nm. We show results of a 200 μm NA0.22 fiber coupled 35 W source @ 450 nm, which has been reduced in size by a factor of 25 compared to standard single emitter approach. In addition, we will present a 200 μm NA0.22 fiber coupled laser unit with an output power of 135 W.

Modeling bidirectionally coupled single-mode semiconductor lasers

International Nuclear Information System (INIS)

Mulet, Josep; Masoller, Cristina; Mirasso, Claudio R.

2002-01-01

We develop a dynamical model suitable for the description of two mutually coupled semiconductor lasers in a face-to-face configuration. Our study considers the propagation of the electric field along the compound system as well as the evolution of the carrier densities within each semiconductor laser. Mutual injection, passive optical feedback, and multiple reflections are accounted for in this framework, although under weak to moderate coupling conditions. We systematically describe the effect of the coupling strength on the spectrum of monochromatic solutions and on the respective dynamical behavior. By assuming single-longitudinal-mode operation, weak mutual coupling and slowly varying approximation, the dynamical model can be reduced to rate equations describing the mutual injection from one laser to its counterpart and vice versa. A good agreement between the complete and simplified models is found for small coupling. For larger coupling, higher-order terms lead to a smaller threshold reduction, reflected itself in the spectrum of the monochromatic solutions and in the dynamics of the optical power

Coupling of laser energy into plasma channels

International Nuclear Information System (INIS)

Dimitrov, D. A.; Giacone, R. E.; Bruhwiler, D. L.; Busby, R.; Cary, J. R.; Geddes, C. G. R.; Esarey, E.; Leemans, W. P.

2007-01-01

Diffractive spreading of a laser pulse imposes severe limitations on the acceleration length and maximum electron energy in the laser wake field accelerator (LWFA). Optical guiding of a laser pulse via plasma channels can extend the laser-plasma interaction distance over many Rayleigh lengths. Energy efficient coupling of laser pulses into and through plasma channels is very important for optimal LWFA performance. Results from simulation parameter studies on channel guiding using the particle-in-cell (PIC) code VORPAL [C. Nieter and J. R. Cary, J. Comput. Phys. 196, 448 (2004)] are presented and discussed. The effects that density ramp length and the position of the laser pulse focus have on coupling into channels are considered. Moreover, the effect of laser energy leakage out of the channel domain and the effects of tunneling ionization of a neutral gas on the guided laser pulse are also investigated. Power spectral diagnostics were developed and used to separate pump depletion from energy leakage. The results of these simulations show that increasing the density ramp length decreases the efficiency of coupling a laser pulse to a channel and increases the energy loss when the pulse is vacuum focused at the channel entrance. Then, large spot size oscillations result in increased energy leakage. To further analyze the coupling, a differential equation is derived for the laser spot size evolution in the plasma density ramp and channel profiles are simulated. From the numerical solution of this equation, the optimal spot size and location for coupling into a plasma channel with a density ramp are determined. This result is confirmed by the PIC simulations. They show that specifying a vacuum focus location of the pulse in front of the top of the density ramp leads to an actual focus at the top of the ramp due to plasma focusing, resulting in reduced spot size oscillations. In this case, the leakage is significantly reduced and is negligibly affected by ramp length

Properties of regular polygons of coupled microring resonators.

Science.gov (United States)

Chremmos, Ioannis; Uzunoglu, Nikolaos

2007-11-01

The resonant properties of a closed and symmetric cyclic array of N coupled microring resonators (coupled-microring resonator regular N-gon) are for the first time determined analytically by applying the transfer matrix approach and Floquet theorem for periodic propagation in cylindrically symmetric structures. By solving the corresponding eigenvalue problem with the field amplitudes in the rings as eigenvectors, it is shown that, for even or odd N, this photonic molecule possesses 1 + N/2 or 1+N resonant frequencies, respectively. The condition for resonances is found to be identical to the familiar dispersion equation of the infinite coupled-microring resonator waveguide with a discrete wave vector. This result reveals the so far latent connection between the two optical structures and is based on the fact that, for a regular polygon, the field transfer matrix over two successive rings is independent of the polygon vertex angle. The properties of the resonant modes are discussed in detail using the illustration of Brillouin band diagrams. Finally, the practical application of a channel-dropping filter based on polygons with an even number of rings is also analyzed.

Resonant laser ablation: mechanisms and applications

International Nuclear Information System (INIS)

Anderson, J.E.; Bodla, R.; Eiden, G.C.; Nogar, N.S.; Smith, C.H.

1996-01-01

Resonant laser ablation (RLA) typically relies on irradiation of a sample in a mass spectrometer with modest intensity laser pulses tuned to a one or two photon resonant transition in the analyte of interest. This paper shows that RLA is well suited for highly sensitive analyses of complex samples. The examples actually studied are trace components in rhenium and technetium in nickel. The authors also studied the 2+1 multiphoton ionization spectrum of iron-56 detected by RLA of Re containing 70 ppm iron. Two-photon transition rates for Fe transitions were calculated perturbatively and found to agree semi-quantitatively with experimentally observed intensities. 17 refs., 3 figs

Optical Analysis of Grazing Incidence Ring Resonators for Free-Electron Lasers

Science.gov (United States)

Gabardi, David Richard

1990-08-01

The design of resonators for free-electron lasers (FELs) which are to operate in the soft x-ray/vacuum ultraviolet (XUV) region of the spectrum is complicated by the fact that, in this wavelength regime, normal incidence mirrors, which would otherwise be used for the construction of the resonators, generally have insufficient reflectivities for this purpose. However, the use of grazing incidence mirrors in XUV resonators offers the possibility of (1) providing sufficient reflectivity, (2) a lessening of the mirrors' thermal loads due to the projection of the laser beam onto an oblique surface, and (3) the preservation of the FEL's tunability. In this work, the behavior of resonators employing grazing incidence mirrors in ring type configurations is explored. In particular, two designs, each utilizing four off-axis conic mirrors and a number of flats, are examined. In order to specify the location, orientation, and surface parameters for the mirrors in these resonators, a design algorithm has been developed based upon the properties of Gaussian beam propagation. Two computer simulation methods are used to perform a vacuum stability analysis of the two resonator designs. The first method uses paraxial ray trace techniques with the resonators' thin lens analogues while the second uses the diffraction-based computer simulation code GLAD (General Laser Analysis and Design). The effects of mirror tilts and deviations in the mirror surface parameters are investigated for a number of resonators designed to propagate laser beams of various Rayleigh ranges. It will be shown that resonator stability decreases as the laser wavelength for which the resonator was designed is made smaller. In addition, resonator stability will also be seen to decrease as the amount of magnification the laser beam receives as it travels around the resonator is increased.

Cavity-enhanced resonant photoacoustic spectroscopy with optical feedback cw diode lasers: A novel technique for ultratrace gas analysis and high-resolution spectroscopy.

Science.gov (United States)

Hippler, Michael; Mohr, Christian; Keen, Katherine A; McNaghten, Edward D

2010-07-28

Cavity-enhanced resonant photoacoustic spectroscopy with optical feedback cw diode lasers (OF-CERPAS) is introduced as a novel technique for ultratrace gas analysis and high-resolution spectroscopy. In the scheme, a single-mode cw diode laser (3 mW, 635 nm) is coupled into a high-finesse linear cavity and stabilized to the cavity by optical feedback. Inside the cavity, a build-up of laser power to at least 2.5 W occurs. Absorbing gas phase species inside the cavity are detected with high sensitivity by the photoacoustic effect using a microphone embedded in the cavity. To increase sensitivity further, coupling into the cavity is modulated at a frequency corresponding to a longitudinal resonance of an organ pipe acoustic resonator (f=1.35 kHz and Q approximately 10). The technique has been characterized by measuring very weak water overtone transitions near 635 nm. Normalized noise-equivalent absorption coefficients are determined as alpha approximately 4.4x10(-9) cm(-1) s(1/2) (1 s integration time) and 2.6x10(-11) cm(-1) s(1/2) W (1 s integration time and 1 W laser power). These sensitivities compare favorably with existing state-of-the-art techniques. As an advantage, OF-CERPAS is a "zero-background" method which increases selectivity and sensitivity, and its sensitivity scales with laser power.

Resonant laser printing of structural colors on high-index dielectric metasurfaces

DEFF Research Database (Denmark)

Zhu, Xiaolong; Yan, Wei; Levy, Uriel

2017-01-01

-dependent resonances. Strong on-resonance energy absorption under pulsed laser irradiation locally elevates the lattice temperature (exceeding 1200 K) in an ultrashort time scale (1 ns). This forms the basis for resonant laser printing, where rapid melting allows for surface energy-driven morphology changes...

Q-Boosted Optomechanical Resonators

Science.gov (United States)

2015-11-18

type a knob for optical Qo, where the inability to smooth etched nitride sidewall surfaces relegates OMO’s using it to Qo’s on the order of...6: Operation of an RP-OMO. As the ring resonator coupled to tapered fiber in (a) displaces by ∂r, the optical path length change produces the shift...frequency 0, B input pump laser field, tot the total optical resonator damping, ext the coupling between optical resonator and the tapered fiber

Cyclotron resonance cooling by strong laser field

International Nuclear Information System (INIS)

Tagcuhi, Toshihiro; Mima, Kunioka

1995-01-01

Reduction of energy spread of electron beam is very important to increase a total output radiation power in free electron lasers. Although several cooling systems of particle beams such as a stochastic cooling are successfully operated in the accelerator physics, these cooling mechanisms are very slow and they are only applicable to high energy charged particle beams of ring accelerators. We propose here a new concept of laser cooling system by means of cyclotron resonance. Electrons being in cyclotron motion under a strong magnetic field can resonate with circular polarized electromagnetic field, and the resonance take place selectively depending on the velocity of the electrons. If cyclotron frequency of electrons is equal to the frequency of the electromagnetic field, they absorb the electromagnetic field energy strongly, but the other electrons remain unchanged. The absorbed energy will be converted to transverse kinetic energy, and the energy will be dumped into the radiation energy through bremastrahlung. To build a cooling system, we must use two laser beams, where one of them is counter-propagating and the other is co-propagating with electron beam. When the frequency of the counter-propagating laser is tuned with the cyclotron frequency of fast electrons and the co-propagating laser is tuned with the cyclotron frequency of slow electrons, the energy of two groups will approach and the cooling will be achieved. We solve relativistic motions of electrons with relativistic radiation dumping force, and estimate the cooling rate of this mechanism. We will report optimum parameters for the electron beam cooling system for free electron lasers

Apodized coupled resonator waveguides.

Science.gov (United States)

Capmany, J; Muñoz, P; Domenech, J D; Muriel, M A

2007-08-06

In this paper we propose analyse the apodisation or windowing of the coupling coefficients in the unit cells of coupled resonator waveguide devices (CROWs) as a means to reduce the level of secondary sidelobes in the bandpass characteristic of their transfer functions. This technique is regularly employed in the design of digital filters and has been applied as well in the design of other photonic devices such as corrugated waveguide filters and fiber Bragg gratings. The apodisation of both Type-I and Type-II structures is discussed for several windowing functions.

Effect of couplings in the resonance continuum

International Nuclear Information System (INIS)

Royal, J; Larson, A; Orel, A E

2004-01-01

Electronic coupling of two or more resonances via the electron scattering continuum is investigated. The effect of this coupling as a function of the resonance curves and autoionization widths is investigated, and the conditions for the maximum effect are determined. The theory is applied to two physical problems, the product state distribution produced by the dissociative recombination of electrons with HeH + and a one-dimensional model for ion-pair production resulting from electron collisions with H + 3 . It is found that the coupling does not affect the product state distribution in HeH + but produces a significant effect in the H + 3 model

Predictive values of Bi-Rads categories 3, 4 and 5 in non-palpable breast masses evaluated by mammography, ultrasound and magnetic resonance imaging

International Nuclear Information System (INIS)

Roveda Junior, Decio; Fleury, Eduardo de Castro Faria; Piato, Sebastiao; Oliveira, Vilmar Marques de; Rinaldi, Jose Francisco; Ferreira, Carlos Alberto Pecci

2007-01-01

Objective: To evaluate the predictive value of BI-RADS TM categories 3, 4 and 5 in non-palpable breast masses assessed by mammography, ultrasound and magnetic resonance imaging. Materials And Methods: Twenty-nine patients with BI-RADS categories 3, 4 and 5 non-palpable breast masses identified by mammograms were submitted to complementary ultrasound and magnetic resonance imaging studies, besides excisional biopsy. In total, 30 biopsies were performed. The lesions as well as their respective BI-RADS classification into 3, 4 and 5 were correlated with the histopathological results. The predictive values calculation was made by means of specific mathematical equations. Results: Negative predictive values for category 3 were: mammography, 69.23%; ultrasound, 70.58%; and magnetic resonance imaging, 100%. Positive predictive values for category 4 were: mammography, 63.63%; ultrasound, 50%; and magnetic resonance imaging, 30.76%. For category 5, positive predictive values were: mammography and ultrasound, 100%; and magnetic resonance imaging, 92.85%. Conclusion: For category 3, the negative predictive value of magnetic resonance imaging was high, and for categories 4 and 5, the positive predictive values of the three modalities were moderate. (author)

Synchronization scenario of two distant mutually coupled semiconductor lasers

DEFF Research Database (Denmark)

Mulet, Josep; Mirasso, Claudio; Heil, Tilmann

2004-01-01

We present numerical and experimental investigations of the synchronization of the coupling-induced instabilities in two distant mutually coupled semiconductor lasers. In our experiments, two similar Fabry-Perot lasers are coupled via their coherent optical fields. Our theoretical framework is ba...

Heteroclinic dynamics of coupled semiconductor lasers with optoelectronic feedback.

Science.gov (United States)

Shahin, S; Vallini, F; Monifi, F; Rabinovich, M; Fainman, Y

2016-11-15

Generalized Lotka-Volterra (GLV) equations are important equations used in various areas of science to describe competitive dynamics among a population of N interacting nodes in a network topology. In this Letter, we introduce a photonic network consisting of three optoelectronically cross-coupled semiconductor lasers to realize a GLV model. In such a network, the interaction of intensity and carrier inversion rates, as well as phases of laser oscillator nodes, result in various dynamics. We study the influence of asymmetric coupling strength and frequency detuning between semiconductor lasers and show that inhibitory asymmetric coupling is required to achieve consecutive amplitude oscillations of the laser nodes. These studies were motivated primarily by the dynamical models used to model brain cognitive activities and their correspondence with dynamics obtained among coupled laser oscillators.

High-slope-efficiency 2.06 μm Ho: YLF laser in-band pumped by a fiber-coupled broadband diode.

Science.gov (United States)

Ji, Encai; Liu, Qiang; Nie, Mingming; Cao, Xuezhe; Fu, Xing; Gong, Mali

2016-03-15

We first demonstrate the laser performance of a compact 2.06 μm Ho: YLF laser resonantly pumped by a broadband fiber-coupled diode. In continuous-wave (CW) operation, maximum output power of 1.63 W, corresponding to a slope efficiency of 89.2%, was obtained with a near diffraction-limited beam quality. In actively Q-switched operation, maximum pulse energy of 1.1 mJ was achieved at the repetition frequency of 100 Hz. The minimum pulse duration was 43 ns. The performance in both the CW and Q-switched regimes indicates that the current fiber-coupled diode in-band pumped Ho: YLF laser has great potential in certain conditions that require several watts of output power or several millijoules of short pulse energy.

Dynamical resonance shift and unification of resonances in short-pulse laser-cluster interaction

Science.gov (United States)

Mahalik, S. S.; Kundu, M.

2018-06-01

Pronounced maximum absorption of laser light irradiating a rare-gas or metal cluster is widely expected during the linear resonance (LR) when Mie-plasma wavelength λM of electrons equals the laser wavelength λ . On the contrary, by performing molecular dynamics (MD) simulations of an argon cluster irradiated by short 5-fs (FWHM) laser pulses it is revealed that, for a given laser pulse energy and a cluster, at each peak intensity there exists a λ —shifted from the expected λM—that corresponds to a unified dynamical LR at which evolution of the cluster happens through very efficient unification of possible resonances in various stages, including (i) the LR in the initial time of plasma creation, (ii) the LR in the Coulomb expanding phase in the later time, and (iii) anharmonic resonance in the marginally overdense regime for a relatively longer pulse duration, leading to maximum laser absorption accompanied by maximum removal of electrons from cluster and also maximum allowed average charge states for the argon cluster. Increasing the laser intensity, the absorption maxima is found to shift to a higher wavelength in the band of λ ≈(1 -1.5 ) λM than permanently staying at the expected λM. A naive rigid sphere model also corroborates the wavelength shift of the absorption peak as found in MD and unequivocally proves that maximum laser absorption in a cluster happens at a shifted λ in the marginally overdense regime of λ ≈(1 -1.5 ) λM instead of λM of LR. The present study is important for guiding an optimal condition laser-cluster interaction experiment in the short-pulse regime.

Synthesis of coupled resonator optical waveguides by cavity aggregation.

Science.gov (United States)

Muñoz, Pascual; Doménech, José David; Capmany, José

2010-01-18

In this paper, the layer aggregation method is applied to coupled resonator optical waveguides. Starting from the frequency transfer function, the method yields the coupling constants between the resonators. The convergence of the algorithm developed is examined and the related parameters discussed.

Laser-Induced Focused Ultrasound for Cavitation Treatment: Toward High-Precision Invisible Sonic Scalpel.

Science.gov (United States)

Lee, Taehwa; Luo, Wei; Li, Qiaochu; Demirci, Hakan; Guo, L Jay

2017-10-01

Beyond the implementation of the photoacoustic effect to photoacoustic imaging and laser ultrasonics, this study demonstrates a novel application of the photoacoustic effect for high-precision cavitation treatment of tissue using laser-induced focused ultrasound. The focused ultrasound is generated by pulsed optical excitation of an efficient photoacoustic film coated on a concave surface, and its amplitude is high enough to produce controllable microcavitation within the focal region (lateral focus <100 µm). Such microcavitation is used to cut or ablate soft tissue in a highly precise manner. This work demonstrates precise cutting of tissue-mimicking gels as well as accurate ablation of gels and animal eye tissues. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Diode lasers optimized in brightness for fiber laser pumping

Science.gov (United States)

Kelemen, M.; Gilly, J.; Friedmann, P.; Hilzensauer, S.; Ogrodowski, L.; Kissel, H.; Biesenbach, J.

2018-02-01

In diode laser applications for fiber laser pumping and fiber-coupled direct diode laser systems high brightness becomes essential in the last years. Fiber coupled modules benefit from continuous improvements of high-power diode lasers on chip level regarding output power, efficiency and beam characteristics resulting in record highbrightness values and increased pump power. To gain high brightness not only output power must be increased, but also near field widths and far field angles have to be below a certain value for higher power levels because brightness is proportional to output power divided by beam quality. While fast axis far fields typically show a current independent behaviour, for broadarea lasers far-fields in the slow axis suffer from a strong current and temperature dependence, limiting the brightness and therefore their use in fibre coupled modules. These limitations can be overcome by carefully optimizing chip temperature, thermal lensing and lateral mode structure by epitaxial and lateral resonator designs and processing. We present our latest results for InGaAs/AlGaAs broad-area single emitters with resonator lengths of 4mm emitting at 976nm and illustrate the improvements in beam quality over the last years. By optimizing the diode laser design a record value of the brightness for broad-area lasers with 4mm resonator length of 126 MW/cm2sr has been demonstrated with a maximum wall-plug efficiency of more than 70%. From these design also pump modules based on 9 mini-bars consisting of 5 emitters each have been realized with 360W pump power.

A resonant ionization laser ion source at ORNL

Energy Technology Data Exchange (ETDEWEB)

Liu, Y.; Stracener, D.W.

2016-06-01

Multi-step resonance laser ionization has become an essential tool for the production of isobarically pure radioactive ion beams at the isotope separator on-line (ISOL) facilities around the world. A resonant ionization laser ion source (RILIS) has been developed for the former Holifield Radioactive Ion Beam Facility (HRIBF) of Oak Ridge National Laboratory. The RILIS employs a hot-cavity ion source and a laser system featuring three grating-tuned and individually pumped Ti:Sapphire lasers, especially designed for stable and simple operation. The RILIS has been installed at the second ISOL production platform of former HRIBF and has successfully provided beams of exotic neutron-rich Ga isotopes for beta decay studies. This paper reports the features, advantages, limitations, and on-line and off-line performance of the RILIS.

Lithographic wavelength control of an external cavity laser with a silicon photonic crystal cavity-based resonant reflector.

Science.gov (United States)

Liles, Alexandros A; Debnath, Kapil; O'Faolain, Liam

2016-03-01

We report the experimental demonstration of a new design for external cavity hybrid lasers consisting of a III-V semiconductor optical amplifier (SOA) with fiber reflector and a photonic crystal (PhC)-based resonant reflector on SOI. The silicon reflector is composed of an SU8 polymer bus waveguide vertically coupled to a PhC cavity and provides a wavelength-selective optical feedback to the laser cavity. This device exhibits milliwatt-level output power and side-mode suppression ratios of more than 25 dB.

Laser Ultrasound Spectroscopy Scanning for 3D Printed Parts

Energy Technology Data Exchange (ETDEWEB)

Brennan, Guendalyn Kendra [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-08-04

One of the challenges of additive manufacturing is quality control due to the possibility of unseen flaws in the final product. The current methods of inspection are lacking in detail, too slow for practical use, or unable to validate internal structure. This report examines the use of laser ultrasound spectroscopy in layer by layer scans of 3D printed parts as they are created. The result is fast and detailed quality control. An additional advantage of this method is the ability to cancel a print as soon as a defect is detected, therefore saving materials and time. This technique, though simple in concept, has been a challenge to implement. I discuss tweaking the 3D printer configuration, and finding the optimal settings for laser scanning small parts made of ABS plastic, as well as the limits of how small of a detail the laser can detect. These settings include the frequency of the ultrasonic transducer, the speed of the laser, and the distance from the laser to the part.

Critical Coupling Between Optical Fibers and WGM Resonators

Science.gov (United States)

Matsko, Andrey; Maleki, Lute; Itchenko, Vladimir; Savchenkov, Anatoliy

2009-01-01

Two recipes for ensuring critical coupling between a single-mode optical fiber and a whispering-gallery-mode (WGM) optical resonator have been devised. The recipes provide for phase matching and aperture matching, both of which are necessary for efficient coupling. There is also a provision for suppressing intermodal coupling, which is detrimental because it drains energy from desired modes into undesired ones. According to one recipe, the tip of the single-mode optical fiber is either tapered in diameter or tapered in effective diameter by virtue of being cleaved at an oblique angle. The effective index of refraction and the phase velocity at a given position along the taper depend on the diameter (or effective diameter) and the index of refraction of the bulk fiber material. As the diameter (or effective diameter) decreases with decreasing distance from the tip, the effective index of refraction also decreases. Critical coupling and phase matching can be achieved by placing the optical fiber and the resonator in contact at the proper point along the taper. This recipe is subject to the limitation that the attainable effective index of refraction lies between the indices of refraction of the bulk fiber material and the atmosphere or vacuum to which the resonator and fiber are exposed. The other recipe involves a refinement of the previously developed technique of prism coupling, in which the light beam from the optical fiber is collimated and focused onto one surface of a prism that has an index of refraction greater than that of the resonator. Another surface of the prism is placed in contact with the resonator. The various components are arranged so that the collimated beam is focused at the prism/resonator contact spot. The recipe includes the following additional provisions:

Continuous-wave generation and tunability of eye-safe resonantly diode-pumped Er:YAG laser

Science.gov (United States)

Němec, Michal; Indra, Lukás.; Šulc, Jan; Jelínková, Helena

2016-03-01

Laser sources generating radiation in the spectral range from 1.5 to 1.7 μm are very attractive for many applications such as satellite communication, range finding, spectroscopy, and atmospheric sensing. The goal of our research was an investigation of continuous-wave generation and wavelength tuning possibility of diode pumped eye-safe Er:YAG laser emitting radiation around 1645 nm. We used two 0.5 at. % doped Er:YAG active media with lengths of 10 mm and 25 mm (diameter 5 mm). As a pumping source, a fibre-coupled 1452 nm laser-diode was utilized, which giving possibility of the in-band pumping with a small quantum defect and low thermal stress of the active bulk laser material. The 150 mm long resonator was formed by a pump mirror (HT @ 1450 nm, HR @ 1610 - 1660 nm) and output coupler with 96 % reflectivity at 1610 - 1660 nm. For continuous-wave generation, the maximal output powers were 0.7 W and 1 W for 10 mm and 25 mm long laser crystals, respectively. The corresponding slope efficiencies with respect to absorbed pump power for these Er:YAG lasers were 26.5 % and 37.8 %, respectively. The beam spatial structure was close to the fundamental Gaussian mode. A wavelength tunability was realized by a birefringent plate and four local spectral maxima at 1616, 1633, 1645, and 1657 nm were reached. The output characteristics of the designed and realized resonantly diode-pumped eye-safe Er:YAG laser show that this compact system has a potential for usage mainly in spectroscopic fields.

Novel Electro-Optical Coupling Technique for Magnetic Resonance-Compatible Positron Emission Tomography Detectors

Directory of Open Access Journals (Sweden)

Peter D. Olcott

2009-03-01

Full Text Available A new magnetic resonance imaging (MRI-compatible positron emission tomography (PET detector design is being developed that uses electro-optical coupling to bring the amplitude and arrival time information of high-speed PET detector scintillation pulses out of an MRI system. The electro-optical coupling technology consists of a magnetically insensitive photodetector output signal connected to a nonmagnetic vertical cavity surface emitting laser (VCSEL diode that is coupled to a multimode optical fiber. This scheme essentially acts as an optical wire with no influence on the MRI system. To test the feasibility of this approach, a lutetium-yttrium oxyorthosilicate crystal coupled to a single pixel of a solid-state photomultiplier array was placed in coincidence with a lutetium oxyorthosilicate crystal coupled to a fast photomultiplier tube with both the new nonmagnetic VCSEL coupling and the standard coaxial cable signal transmission scheme. No significant change was observed in 511 keV photopeak energy resolution and coincidence time resolution. This electro-optical coupling technology enables an MRI-compatible PET block detector to have a reduced electromagnetic footprint compared with the signal transmission schemes deployed in the current MRI/PET designs.

Novel electro-optical coupling technique for magnetic resonance-compatible positron emission tomography detectors.

Science.gov (United States)

Olcott, Peter D; Peng, Hao; Levin, Craig S

2009-01-01

A new magnetic resonance imaging (MRI)-compatible positron emission tomography (PET) detector design is being developed that uses electro-optical coupling to bring the amplitude and arrival time information of high-speed PET detector scintillation pulses out of an MRI system. The electro-optical coupling technology consists of a magnetically insensitive photodetector output signal connected to a nonmagnetic vertical cavity surface emitting laser (VCSEL) diode that is coupled to a multimode optical fiber. This scheme essentially acts as an optical wire with no influence on the MRI system. To test the feasibility of this approach, a lutetium-yttrium oxyorthosilicate crystal coupled to a single pixel of a solid-state photomultiplier array was placed in coincidence with a lutetium oxyorthosilicate crystal coupled to a fast photomultiplier tube with both the new nonmagnetic VCSEL coupling and the standard coaxial cable signal transmission scheme. No significant change was observed in 511 keV photopeak energy resolution and coincidence time resolution. This electro-optical coupling technology enables an MRI-compatible PET block detector to have a reduced electromagnetic footprint compared with the signal transmission schemes deployed in the current MRI/PET designs.

THE POSSIBILITY OF USING LASER-ULTRASOUND TO MONITOR THE QUALITY SOLDERED CONNECTIONS CHAMBERS OF LIQUID ROCKET ENGINES

Directory of Open Access Journals (Sweden)

N. V. Astredinova

2014-01-01

Full Text Available During the manufacturing process to the design of modern liquid rocket engines are presented important requirements, such as minimum weight, maximum stiffness and strength of nodes, maximum service life in operation, high reliability and quality of soldered and welded seams. Due to the high quality requirements soldered connections and the specific design of the nozzle, it became necessary in the development and testing of a new non-conventional non-destructive testing method – laser-ultrasound diagnosis. In accordance with regulatory guidelines, quality control soldered connections is allowed to use an acoustic kind of control methods of the reflected light, transmitted light, resonant, free vibration and acoustic emission. Attempts to use traditional methods of non-destructive testing did not lead to positive results. This is due primarily to the size of typical solder joint defects, as well as the structural features of the rocket engine, the data structure is not controllable. In connection with this, a new method that provides quality control soldered connections cameras LRE based on the thermo generation of ultrasound. Methods of ultrasonic flaw detection of photoacoustic effect, in most cases, have a number of advantages over methods that use standard (traditional piezo transducers. In the course of studies have found that the sensitivity of the laser-ultrasonic method and flaw detector UDL-2M can detect lack of adhesion in the solder joints on the upper edges of the nozzle in the sub-header area of the site.

Radiation reaction effect on laser driven auto-resonant particle acceleration

International Nuclear Information System (INIS)

Sagar, Vikram; Sengupta, Sudip; Kaw, P. K.

2015-01-01

The effects of radiation reaction force on laser driven auto-resonant particle acceleration scheme are studied using Landau-Lifshitz equation of motion. These studies are carried out for both linear and circularly polarized laser fields in the presence of static axial magnetic field. From the parametric study, a radiation reaction dominated region has been identified in which the particle dynamics is greatly effected by this force. In the radiation reaction dominated region, the two significant effects on particle dynamics are seen, viz., (1) saturation in energy gain by the initially resonant particle and (2) net energy gain by an initially non-resonant particle which is caused due to resonance broadening. It has been further shown that with the relaxation of resonance condition and with optimum choice of parameters, this scheme may become competitive with the other present-day laser driven particle acceleration schemes. The quantum corrections to the Landau-Lifshitz equation of motion have also been taken into account. The difference in the energy gain estimates of the particle by the quantum corrected and classical Landau-Lifshitz equation is found to be insignificant for the present day as well as upcoming laser facilities

Evidence for trapping and collectivization of resonances at strong coupling

International Nuclear Information System (INIS)

Herzberg, R.D.; Brentano, P. von; Rotter, I.

1993-01-01

The behavior of 22 neutron resonances in 53 Cr is investigated as a function of the coupling-strength parameter μ and of the degree of overlapping. Starting from a doorway picture at small μ, the widths of 21 resonances increase with increasing μ at the cost of the width of the original 'single-particle doorway resonance'. At μ≅1, the widths of most states decrease again. At μ→10 the widths of these 'trapped' states vanish while 'collective' states are formed which gather the widths. Thus we again observe a doorway picture at strong coupling. At μ=1, the energies and widths of the resonances are fitted to the experimental data. At this coupling strength, most resonances investigated resemble trapped modes. (orig.)

Nd:YAG (2 omega) pumped dye laser using self-filtering unstable resonator

CERN Document Server

Rahimian, K; Hariri, H

2002-01-01

A self-filtering unstable resonator with a magnification of M=-3 in a Nd:YAG (2 omega) dye laser has been studied. The dye solution is Rhodamine 6 G in alcohol with the concentration of 5*10 sub - 3 Mol/lit. The spatial intensity distribution of the resonator has been compared has been compared with that of a plane-parallel resonator of equal length. The output energy in both configurations are comparable (20 mu J ,and 26 mu J ,respectively). A significant difference between these two resonators is the laser beam divergence, where beam divergences of 0.77 mrad for the self-filtering unstable resonator and 1.6 mrad for the plane-parallel resonator have been measured. The brightness corresponding to these two resonators are 1.5* 10 sub 1 1 and 2.2* 10 sub 1 0W.cm sub - 2.Sr sub - 1, and the pulse widths are 7 and 17 ns, respectively. These figures show clearly that laser resonator based on the self-filtering unstable resonator design an increase the laser brightness a factor of 10, with a beam divergence of a f...

Laser generated ultrasound sources using polymer nanocomposites for high frequency metrology

KAUST Repository

Rajagopal, Srinath

2017-11-22

Accurate characterisation of ultrasound fields generated by diagnostic and therapeutic transducers is critical for patient safety. This requires hydrophones calibrated to a traceable standard. The existing implementation of the primary standard at the National Measurement Institutes, e.g., NPL and PTB, can provide accurate calibration to a maximum frequency of 40MHz. However, the increasing use of high frequencies for both imaging and therapy necessitates calibrations to frequencies well beyond this range. For this to be possible, a source of high amplitude, broadband, quasi-planar and stable ultrasound fields is required. This is difficult to achieve using conventional piezoelectric sources, but laser generated ultrasound is a promising technique in this regard. In this study various polymer-carbon nanotube nanocomposites (PNC) were fabricated and tested for their suitability for such an application.

Resonant excitation of uranium atoms by an argon ion laser

Energy Technology Data Exchange (ETDEWEB)

Maeyama, H; Morikawa, M; Aihara, Y; Mochizuki, T; Yamanaka, C [Osaka Univ. (Japan)

1979-03-01

Photoionization of uranium atoms by UV lines, 3511 A and 3345 A, of an argon ion laser was observed and attributed due to resonant two-photon ionization. The dependence of the photoion currents on laser power was measured in focusing and non-focusing modes of laser beam, which has enabled us to obtain an absorption cross section and an ionization cross section independently. The orders of magnitude of these cross sections averaged over the fine structure were determined to be 10/sup -14/ cm/sup 2/ and 10/sup -17/ cm/sup 2/ respectively from a rate equation model. Resonance between 3511-A laser line and the absorption line of uranium isotopes was also confirmed by the ionization spectra obtained by near-single-frequency operation of the ion laser, which allowed the isotopic selective excitation of the uranium atoms. The maximum value of the enrichment of /sup 235/U was about 14%. The isotope separation of uranium atoms by this resonant excitation has been discussed.

In Situ Coupling of Ultrasound to Electro- and Photo-Deposition Methods for Materials Synthesis

Directory of Open Access Journals (Sweden)

Agnieszka Magdziarz

2017-01-01

Full Text Available This short review provides the current state-of-the-art of in situ coupling of ultrasound to chemical deposition methods. A synergetic action of the ultrasound and light radiation or electrical fields may result in new powerful methodologies, and these include sonophotodeposition and sonoelectrodeposition processes. The effect of ultrasound is explained on the base of different physical mechanisms emerging from cavitation phenomenon. Some possible mechanisms of the interactions between ultrasound and photochemical and electrochemical processes are discussed here. The application of sonophotodeposition and sonoelectrodeposition as green energy sources in the syntheses of different nanomaterials is also reviewed.

Circular lasers for telecommunications and rf/photonics applications

Science.gov (United States)

Griffel, Giora

2000-04-01

Following a review of ring resonator research in the past decade we shall report a novel bi-level etching technique that permits the use of standard photolithography for coupling to deeply-etched ring resonator structures. The technique is employed to demonstrate InGaAsP laterally- coupled racetrack ring resonators laser with record low threshold currents of 66 mA. The racetrack laser have curved sections of 150 micrometers radius with negligible bending loss. The lasers operate CW single mode up to nearly twice threshold with a 26 dB side-mode-suppression ratio. We shall also present a transfer matrix formalism for the analysis of ring resonator arrays and indicate application examples for flat band filter synthesis.

Interference of laser-induced resonances in the continuous structures of a helium atom

International Nuclear Information System (INIS)

Magunov, A I; Strakhova, S I

2003-01-01

Coherent effects in the interference of overlapping laser-induced resonances in helium atoms are considered. The simultaneous action of single-mode radiation of the 294-nm second harmonic of a cw dye laser and a 1064-nm Nd:YAG laser on helium atoms provides the overlap of two resonances induced by transitions from the 1s2s 1 S and 1s4s 1 S helium levels. The shape of the overlapping laser-induced resonances in the rotating-wave approximation is described by analytic expressions, which depend on the laser radiation intensities and the ratio of laser frequencies. (nonlinear optical phenomena)

Resonator coupled Josephson junctions; parametric excitations and mutual locking

DEFF Research Database (Denmark)

Jensen, H. Dalsgaard; Larsen, A.; Mygind, Jesper

1991-01-01

Self-pumped parametric excitations and mutual locking in systems of Josephson tunnel junctions coupled to multimode resonators are reported. For the very large values of the coupling parameter, obtained with small Nb-Al2O3-Nb junctions integrated in superconducting microstrip resonators, the DC I......-V characteristic shows an equidistant series of current steps generated by subharmonic pumping of the fundamental resonator mode. This is confirmed by measurement of frequency and linewidth of the emitted Josephson radiation...

In-Process Detection of Weld Defects Using Laser-Based Ultrasound

International Nuclear Information System (INIS)

Bacher, G.D.; Kercel, S.W.; Kisner, R.A.; Klein, M.B.; Pouet, B.

1999-01-01

Laser-based ultrasonic (LBU) measurement shows great promise for on-line monitoring of weld quality in tailor-welded blanks. Tailor-welded blanks are steel blanks made from plates of differing thickness and/or properties butt-welded together; they are used in automobile manufacturing to produce body, frame, and closure panels. LBU uses a pulsed laser to generate the ultrasound and a continuous wave (CW) laser interferometer to detect the ultrasound at the point of interrogation to perform ultrasonic inspection. LBU enables in-process measurements since there is no sensor contact or near-contact with the workpiece. The authors are using laser-generated plate (Lamb) waves to propagate from one plate into the weld nugget as a means of detecting defects. This paper reports the results of the investigation of a number of inspection architectures based on processing of signals from selected plate waves, which are either reflected from or transmitted through the weld zone. Bayesian parameter estimation and wavelet analysis (both continuous and discrete) have shown that the LBU time-series signal is readily separable into components that provide distinguishing features which describe weld quality. The authors anticipate that, in an on-line industrial application, these measurements can be implemented just downstream from the weld cell. Then the weld quality data can be fed back to control critical weld parameters or alert the operator of a problem requiring maintenance. Internal weld defects and deviations from the desired surface profile can then be corrected before defective parts are produced

Double resonance modulation characteristics of optically injection-locked Fabry–Perot lasers

International Nuclear Information System (INIS)

Dorogush, E S; Afonenko, A A

2015-01-01

The distributed resonator model is used to show the presence of several resonance responses on the modulation characteristic of optically injection-locked Fabry–Perot lasers. The positions of the resonance peaks on the modulation characteristic are determined by the resonator length and frequency detuning of optical injection. It is shown that an appropriate choice of the resonator length and injection locking conditions allows one to obtain efficient modulation in two ranges near 40 – 60 GHz or to increase the direct modulation bandwidth up to 50 GHz. (control of laser radiation parameters)

Double resonance modulation characteristics of optically injection-locked Fabry–Perot lasers

Energy Technology Data Exchange (ETDEWEB)

Dorogush, E S; Afonenko, A A [Belarusian State University, Minsk (Belarus)

2015-12-31

The distributed resonator model is used to show the presence of several resonance responses on the modulation characteristic of optically injection-locked Fabry–Perot lasers. The positions of the resonance peaks on the modulation characteristic are determined by the resonator length and frequency detuning of optical injection. It is shown that an appropriate choice of the resonator length and injection locking conditions allows one to obtain efficient modulation in two ranges near 40 – 60 GHz or to increase the direct modulation bandwidth up to 50 GHz. (control of laser radiation parameters)

Laser modes and threshold condition i N-mirror resonator

DEFF Research Database (Denmark)

Pedersen, Christian; Skettrup, Torben

1996-01-01

Two formal methods for finding laser modes and threshold conditions in laser resonators containing as many as N mirrors are presented. The first method is based on an analysis determining the reflectivity and the transmittivity of an N-mirror system with gain. This is an extension of the classical...... 2 × 2 matrix method. The second method is based on self-consistency equations for the system and directly yields the circulating fields of the individual resonators. A set of rules has been proved to allow these fields to be calculated directly by means of inspection. The laser oscillation condition...

Current developments with TRIUMF’s titanium-sapphire laser based resonance ionization laser ion source

Energy Technology Data Exchange (ETDEWEB)

Lassen, J., E-mail: LASSEN@triumf.ca; Li, R. [TRIUMF (Canada); Raeder, S. [GSI Helmholtzzentrum für Schwerionenforschung GmbH (Germany); Zhao, X.; Dekker, T. [TRIUMF (Canada); Heggen, H. [GSI Helmholtzzentrum für Schwerionenforschung GmbH (Germany); Kunz, P.; Levy, C. D. P.; Mostanmand, M.; Teigelhöfer, A.; Ames, F. [TRIUMF (Canada)

2017-11-15

Developments at TRIUMF’s isotope separator and accelerator (ISAC) resonance ionization laser ion source (RILIS) in the past years have concentrated on increased reliability for on-line beam delivery of radioactive isotopes to experiments, as well as increasing the number of elements available through resonance ionization and searching for ionization schemes with improved efficiency. The current status of these developments is given with a list of two step laser ionization schemes implemented recently.

Study on 2D arbitrary geometry coupling resonance method

International Nuclear Information System (INIS)

He Lei; Wu Hongchun; Cao Liangzhi

2014-01-01

The paper firstly proposes a coupling resonance method in which subgroup method is employed in the serried peak energy region, and wavelet expansion method is employed in single peak energy region. The original subgroup model and wavelet expansion model are improved and coupled through the calculation of scattering source from subgroup to wavelet expansion, so that the self-shielding cross section in the whole energy region can be calculated accurately. To verify these theories and to prove the improvements, a PWR cell benchmark problem is calculated. It is demonstrated that, compared with other traditional multi-group resonance methods and continuous energy resonance method, this coupling resonance method has the ability to accurately calculate the whole energy region's self-shielding cross section while Keeping enough efficiency and finally has an ability to offer the accurate self-shielding parameters for latter transport, calculation. (authors)

Laser Beam and Resonator Calculations on Desktop Computers.

Science.gov (United States)

Doumont, Jean-Luc

There is a continuing interest in the design and calculation of laser resonators and optical beam propagation. In particular, recently, interest has increased in developing concepts such as one-sided unstable resonators, supergaussian reflectivity profiles, diode laser modes, beam quality concepts, mode competition, excess noise factors, and nonlinear Kerr lenses. To meet these calculation needs, I developed a general-purpose software package named PARAXIA ^{rm TM}, aimed at providing optical scientists and engineers with a set of powerful design and analysis tools that provide rapid and accurate results and are extremely easy to use. PARAXIA can handle separable paraxial optical systems in cartesian or cylindrical coordinates, including complex-valued and misaligned ray matrices, with full diffraction effects between apertures. It includes the following programs:. ABCD provides complex-valued ray-matrix and gaussian -mode analyses for arbitrary paraxial resonators and optical systems, including astigmatism and misalignment in each element. This program required that I generalize the theory of gaussian beam propagation to the case of an off-axis gaussian beam propagating through a misaligned, complex -valued ray matrix. FRESNEL uses FFT and FHT methods to propagate an arbitrary wavefront through an arbitrary paraxial optical system using Huygens' integral in rectangular or radial coordinates. The wavefront can be multiplied by an arbitrary mirror profile and/or saturable gain sheet on each successive propagation through the system. I used FRESNEL to design a one-sided negative-branch unstable resonator for a free -electron laser, and to show how a variable internal aperture influences the mode competition and beam quality in a stable cavity. VSOURCE implements the virtual source analysis to calculate eigenvalues and eigenmodes for unstable resonators with both circular and rectangular hard-edged mirrors (including misaligned rectangular systems). I used VSOURCE to

Femtosecond pulse with THz repetition frequency based on the coupling between quantum emitters and a plasmonic resonator

Science.gov (United States)

Li, Shilei; Ding, Yinxing; Jiao, Rongzhen; Duan, Gaoyan; Yu, Li

2018-03-01

Nanoscale pulsed light is highly desirable in nano-integrated optics. In this paper, we obtained femtosecond pulses with THz repetition frequency via the coupling between quantum emitters (QEs) and plasmonic resonators. Our structure consists of a V -groove (VG) plasmonic resonator and a nanowire embedded with two-level QEs. The influences of the incident light intensity and QE number density on the transmission response for this hybrid system are investigated through semiclassical theory and simulation. The results show that the transmission response can be modulated to the pulse form. And the repetition frequency and extinction ratio of the pulses can be controlled by the incident light intensity and QE number density. The reason is that the coupling causes the output power of nanowire to behave as an oscillating form, the oscillating output power in turn causes the field amplitude in the resonator to oscillate over time. A feedback system is formed between the plasmonic resonator and the QEs in the nanowire. This provides a method for generating narrow pulsed lasers with ultrahigh repetition frequencies in plasmonic systems using a continuous wave input, which has potential applications in generating optical clock signals at the nanoscale.

Unstable Resonator Retrofitted Handheld Laser Designator

Science.gov (United States)

1978-06-01

retrofitted with a negative-branch unstable resona- tor laser and hybrid pump cavity in place of the conventional plane-mirror/ porro prism resonator and...directed by prism B to an expanding telescope, shared with the viewing system of the designator. The actual, unfolded resonator length is approxi...was performed based on using a plane- parallel cavity consisting of a 47% reflectivity output coupler, porro - prism reflector, and the same LiNb03

A Study of Laser-generated Ultrasound for Evaluation of Thickness Reduction in Piping System

International Nuclear Information System (INIS)

Seo, Kyung Chul; Choi, Sang Woo; Lee, Jun Hyun; Kang, Seung Hyun

2005-01-01

In carbon steel pipes of nuclear power plants, local wall thinning may result from erosion-corrosion or FAC(Flow Accelerated Corrosion) damage. Local wall thinning is one of the major causes for the structural fracture of these pipes. Therefore, assessment of local wall thinning due to corrosion is an important issue in nondestructive evaluation for the integrity of nuclear power plants. In this study, laser-generated ultrasound technique was employed to evaluate local wall thinning due to corrosion. Guided waves were generated in the thermoelastic regime using a Q-switched pulsed Nd:YAG laser with an linear array slit. Time-frequency analysis of ultrasonic waveforms using wavelet transform and FRT(Fast Fourier Transform) allowed the identification of generated guided wave modes by comparison with the theoretical dispersion curves. This study shows some experimental results about optimization of generating laser ultrasound using various linear array slits.

Storage and on-demand release of microwaves using superconducting resonators with tunable coupling

International Nuclear Information System (INIS)

Pierre, Mathieu; Svensson, Ida-Maria; Raman Sathyamoorthy, Sankar; Johansson, Göran; Delsing, Per

2014-01-01

We present a system which allows to tune the coupling between a superconducting resonator and a transmission line. This storage resonator is addressed through a second, coupling resonator, which is frequency-tunable and controlled by a magnetic flux applied to a superconducting quantum interference device. We experimentally demonstrate that the lifetime of the storage resonator can be tuned by more than three orders of magnitude. A field can be stored for 18 μs when the coupling resonator is tuned off resonance and it can be released in 14 ns when the coupling resonator is tuned on resonance. The device allows capture, storage, and on-demand release of microwaves at a tunable rate.

Quantum heat engine with coupled superconducting resonators

DEFF Research Database (Denmark)

Hardal, Ali Ümit Cemal; Aslan, Nur; Wilson, C. M.

2017-01-01

We propose a quantum heat engine composed of two superconducting transmission line resonators interacting with each other via an optomechanical-like coupling. One resonator is periodically excited by a thermal pump. The incoherently driven resonator induces coherent oscillations in the other one...... the signatures of quantum behavior in the statistical and thermodynamic properties of the system. We find evidence of a quantum enhancement in the power output of the engine at low temperatures....

Self-optimizing approach for automated laser resonator alignment

Science.gov (United States)

Brecher, C.; Schmitt, R.; Loosen, P.; Guerrero, V.; Pyschny, N.; Pavim, A.; Gatej, A.

2012-02-01

Nowadays, the assembly of laser systems is dominated by manual operations, involving elaborate alignment by means of adjustable mountings. From a competition perspective, the most challenging problem in laser source manufacturing is price pressure, a result of cost competition exerted mainly from Asia. From an economical point of view, an automated assembly of laser systems defines a better approach to produce more reliable units at lower cost. However, the step from today's manual solutions towards an automated assembly requires parallel developments regarding product design, automation equipment and assembly processes. This paper introduces briefly the idea of self-optimizing technical systems as a new approach towards highly flexible automation. Technically, the work focuses on the precision assembly of laser resonators, which is one of the final and most crucial assembly steps in terms of beam quality and laser power. The paper presents a new design approach for miniaturized laser systems and new automation concepts for a robot-based precision assembly, as well as passive and active alignment methods, which are based on a self-optimizing approach. Very promising results have already been achieved, considerably reducing the duration and complexity of the laser resonator assembly. These results as well as future development perspectives are discussed.

Generation of single-frequency tunable green light in a coupled ring tapered diode laser cavity

DEFF Research Database (Denmark)

Jensen, Ole Bjarlin; Petersen, Paul Michael

2013-01-01

in the broad wavelength range from 1049 nm to 1093 nm and the beam propagation factor is improved from M2 = 2.8 to below 1.1. The laser frequency is automatically locked to the cavity resonance frequency using optical feedback. Furthermore, we show that this adaptive external cavity approach leads to efficient......We report the realization of a tapered diode laser operated in a coupled ring cavity that significantly improves the coherence properties of the tapered laser and efficiently generates tunable light at the second harmonic frequency. The tapered diode laser is tunable with single-frequency output...... frequency doubling. More than 500 mW green output power is obtained by placing a periodically poled LiNbO3 crystal in the external cavity. The single frequency green output from the laser system is tunable in the 530 nm to 533 nm range limited by the LiNbO3 crystal. The optical to optical conversion...

Comparison of the effect of low-power laser with therapeutic ultrasound on the treatment of rotator cuff tendonitis

Directory of Open Access Journals (Sweden)

asghar Akbari

2009-01-01

Full Text Available Akbari A1 1. Assistant Professor, Department of Physiotherapy, Faculty of Medicine, Zahedan University of Medical Sciences Abstract Background: Shoulder pain is the third most prevalent cause of musculoskeletal disorder after low back and cervical pains. Most of the shoulder symptoms are attributed to the rotator cuff. The objective of this study was to compare the effects of low-power laser therapy with ultrasound therapy on the patients with rotator cuff tendonitis. Materials and methods: This clinical trial was performed in Zahedan university of medical sciences in 2006. Thirty patients with rotator cuff tendonitis were randomly assigned to either a low-power laser therapy group (15 patients or an ultrasound therapy group (15 patients. Strength (kg of shoulder abductor, and internal and external rotator muscles, as well as range (degree of shoulder abduction, and internal and external rotation were measured before and after intervention using hand-held dynamometer and goniometer respectively. The pain was evaluated using the visual analogue scale. In the laser group, a low-level Ga-As laser was applied with a 100 mw point probe (average power, wave length of 905 nm, pulse duration of 200 ns, 6 J/cm2 dosage, 5 KHz frequency, and lasting 3 minutes. The ultrasound treatment was applied with a power of 1 W/cm2, a frequency of 1 MHz, pulse mode of 1:4, and lasting 10 minutes on each occasion. The treatment was carried out 3 times weekly for 10 days. The data were analyzed using independent sample t-test and paired t-test. Results: The pain in the laser group was significantly decreased from 6.06±1.6 to 5±1.3 in abduction, from 5.3±1.5 to 4.7±1.3 in internal rotation, and from 5.06±1.4 to 4.3±1.44 in external rotation (p0.05. A significant improvement after treatment was observed in the laser group in measures of shoulder abductor, internal rotator and external rotator muscles strength compared to those of the ultrasound therapy group (p<0

The utility of ultrasound and magnetic resonance imaging versus surgery for the characterization of müllerian anomalies in the pediatric and adolescent population.

Science.gov (United States)

Santos, X M; Krishnamurthy, R; Bercaw-Pratt, J L; Dietrich, J E

2012-06-01

To evaluate the utility of transabdominal ultrasound and magnetic resonance imaging in the evaluation of American Society for Reproductive Medicine (†)(ASRM)-classified müllerian anomalies compared to surgical findings in the pediatric and adolescent population. Retrospective chart review. Tertiary academic center. Thirty-eight patients with müllerian anomalies seen in our pediatric and adolescent gynecology clinic were identified both on the basis of ICD-9 codes and having magnetic resonance imaging at Texas Children's Hospital between 2004 and 2009. None. Correlation among transabdominal ultrasound and magnetic resonance imaging findings with surgical findings. Mean age was 12.2 (± 4.1) years. Twenty-eight patients underwent magnetic resonance imaging and required surgical intervention, and 88.5% demonstrated correlative consistency with surgical findings. Twenty-two patients underwent ultrasound, magnetic resonance imaging, and surgery, which revealed consistency among ultrasound and surgical findings (59.1%) and consistency among magnetic resonance imaging and surgical findings (90.9%). In ASRM diagnoses evaluated by magnetic resonance imaging, surgical findings correlated in 92% (Pearson 0.89). Overall, 55.2% of patients had a renal malformation. Magnetic resonance imaging is the gold standard imaging modality for müllerian anomalies and is an effective technique for noninvasive evaluation and accurate classification of the type of anomaly in the pediatric and adolescent population. Magnetic resonance imaging should be considered as an adjunct to transabdominal ultrasound to evaluate müllerian anomalies. Copyright © 2012 North American Society for Pediatric and Adolescent Gynecology. Published by Elsevier Inc. All rights reserved.

Resonant characteristics and sensitivity dependency on the contact surface in QCM-micropillar-based system of coupled resonator sensors

International Nuclear Information System (INIS)

Kashan, M A M; Kalavally, V; Ramakrishnan, N; Lee, H W

2016-01-01

We report the characteristics and sensitivity dependence over the contact surface in coupled resonating sensors (CRSs) made of high aspect ratio resonant micropillars attached to a quartz crystal microbalance (QCM). Through experiments and simulation, we observed that when the pillars of resonant heights were placed in maximum displacement regions the resonance frequency of the QCM increased following the coupled resonance characteristics, as the pillar offered elastic loading to the QCM surface. However, the same pillars when placed in relatively lower displacement regions, in spite of their resonant dimension, offered inertial loading and resulted in a decrease in QCM resonance frequency, as the displacement amplitude was insufficient to couple the vibrations from the QCM to the pillars. Accordingly, we discovered that the coupled resonance characteristics not only depend on the resonant structure dimensions but also on the contact regions in the acoustic device. Further analysis revealed that acoustic pressure at the contact surface also influences the resonance frequency characteristics and sensitivity of the CRS. To demonstrate the significance of the present finding for sensing applications, humidity sensing is considered as the example measurand. When a sensing medium made of resonant SU-8 pillars was placed in a maximum displacement region on a QCM surface, the sensitivity increased by 14 times in comparison to a resonant sensing medium placed in a lower displacement region of a QCM surface. (paper)

Microbubbles coupled to methotrexate-loaded liposomes for ultrasound-mediated delivery of methotrexate across the blood–brain barrier

Directory of Open Access Journals (Sweden)

Wang X

2014-10-01

Full Text Available Xiang Wang,1 Ping Liu,1 Weixiao Yang,1 Lu Li,1 Peijing Li,2 Zheng Liu,1 Zhongxiong Zhuo,1 Yunhua Gao1 1Department of Ultrasound, Xinqiao Hospital of the Third Military Medical University, Chongqing, 2Department of Ultrasound, General Hospital of the Jinan Military Area, Jinan, People’s Republic of China Abstract: Methotrexate (MTX is the single most effective agent for the treatment of primary central nervous system lymphoma. Currently, the delivery of MTX to the brain is achieved by high systemic doses, which cause severe long-term neurotoxicity, or intrathecal administration, which is highly invasive and may lead to infections or hemorrhagic complications. Acoustically active microbubbles have been developed as drug carriers for the noninvasive and brain-targeted delivery of therapeutics. However, their application is limited by their low drug-loading capacity. To overcome this limitation, we prepared microbubbles coupled to MTX-loaded liposomes using ZHIFUXIAN, a novel type of microbubbles with a superior safety profile and long circulation time. MTX-liposome-coupled microbubbles had a high drug-loading capacity of 8.91%±0.86%, and their size (2.64±0.93 µm in diameter was suitable for intravenous injection. When used with ultrasound, they showed more potent in vitro cytotoxicity against Walker-256 cancer cells than MTX alone or MTX-loaded liposomes. When Sprague-Dawley rats were exposed to sonication, administration of these MTX-liposome-coupled microbubbles via the tail vein led to targeted disruption of the blood–brain barrier without noticeable tissue or capillary damage. High-performance liquid chromatography analysis of the brain MTX concentration showed that MTX delivery to the brain followed the order of MTX-liposome-coupled microbubbles + ultrasound (25.3±2.4 µg/g > unmodified ZHIFUXIAN + MTX + ultrasound (18.6±2.2 µg/g > MTX alone (6.97±0.75 µg/g > MTX-liposome-coupled microbubbles (2.92±0.39 µg/g. Therefore

Ultrasound appearance of radiation-induced hepatic injury. Correlation with computed tomography and magnetic resonance imaging

International Nuclear Information System (INIS)

Garra, B.S.; Shawker, T.H.; Chang, R.; Kaplan, K.; White, R.D.

1988-01-01

The ultrasound findings in three cases of radiation-induced hepatic injury are described and compared with computed tomography and magnetic resonance imaging findings. Fatty infiltration of the liver was present in two of the cases in which concurrent chemotherapy was being administered. On ultrasound B-scans, the regions of radiation injury were hypoechoic relative to the remainder of the liver. This finding was more obvious in the patients with fatty livers. CT scans on the patients with fatty infiltrated livers showed higher attenuation in the irradiated region than in unexposed liver. In the patient where no fatty infiltration was present, the radiated section of liver had lower attenuation consistent with previous reports. Magnetic resonance imaging showed decreased signal in the exposed areas on T1 weighted images

Laser-Activated Polymeric Microcapsules for Ultrasound Imaging and Therapy: In Vitro Feasibility

NARCIS (Netherlands)

Lajoinie, Guillaume; van Rooij, Tom; Skachkov, Ilya; Blazejewski, Emilie; Veldhuis, Gert; de Jong, Nico; Kooiman, Klazina; Versluis, Michel

2017-01-01

Polymeric microcapsules with a light-absorbing dye incorporated in their shell can generate vapor microbubbles that can be spatiotemporally controlled by pulsed laser irradiation. These contrast agents of 6–8 μm in diameter can circulate through the vasculature, offering possibilities for ultrasound

Acoustofluidics: theory and simulation of radiation forces at ultrasound resonances in microfluidic devices

DEFF Research Database (Denmark)

Barnkob, Rune; Bruus, Henrik

2009-01-01

Theoretical analysis is combined with numerical simulations to optimize designs and functionalities of acoustofluidic devices, i.e. microfluidic devices in which ultrasound waves are used to anipulate biological particles. The resonance frequencies and corresponding modes of the acoustic fields...... are calculated for various specific geometries of glass/silicon chips containing water-filled microchannels. A special emphasis is put on taking the surrounding glass/silicon material into account, thus going beyond the traditional transverse half-wavelength picture. For the resonance frequencies, where...

Characteristic analysis of a polarization output coupling Porro prism resonator

Science.gov (United States)

Yang, Hailong; Meng, Junqing; Chen, Weibiao

2015-02-01

An Electro-optical Q-switched Nd:YAG slab laser with a crossed misalignment Porro prism resonator for space applications has been theoretically and experimentally investigated. The phase shift induced by the combination of different wave plates and Porro prism azimuth angles have been studied for creating high loss condition prior to Q-switching. The relationship of the effective output coupling reflectivity and the employed Q-switch driving voltage is explored by using Jones matrix optics. In the experiment, the maximum output pulse energy of 93 mJ with 14-ns pulse duration is obtained at the repetition rate of 20 Hz and the optical-to-optical conversion efficiency is 16.8%. The beam quality factors are M 2 x = 2.5 and M 2y = 2.2, respectively.

High-efficiency resonant coupled wireless power transfer via tunable impedance matching

Science.gov (United States)

Anowar, Tanbir Ibne; Barman, Surajit Das; Wasif Reza, Ahmed; Kumar, Narendra

2017-10-01

For magnetic resonant coupled wireless power transfer (WPT), the axial movement of near-field coupled coils adversely degrades the power transfer efficiency (PTE) of the system and often creates sub-resonance. This paper presents a tunable impedance matching technique based on optimum coupling tuning to enhance the efficiency of resonant coupled WPT system. The optimum power transfer model is analysed from equivalent circuit model via reflected load principle, and the adequate matching are achieved through the optimum tuning of coupling coefficients at both the transmitting and receiving end of the system. Both simulations and experiments are performed to evaluate the theoretical model of the proposed matching technique, and results in a PTE over 80% at close coil proximity without shifting the original resonant frequency. Compared to the fixed coupled WPT, the extracted efficiency shows 15.1% and 19.9% improvements at the centre-to-centre misalignment of 10 and 70 cm, respectively. Applying this technique, the extracted S21 parameter shows more than 10 dB improvements at both strong and weak couplings. Through the developed model, the optimum coupling tuning also significantly improves the performance over matching techniques using frequency tracking and tunable matching circuits.

Single-frequency, fully integrated, miniature DPSS laser based on monolithic resonator

Science.gov (United States)

Dudzik, G.; Sotor, J.; Krzempek, K.; Soboń, G.; Abramski, K. M.

2014-02-01

We present a single frequency, stable, narrow linewidth, miniature laser sources operating at 532 nm (or 1064 nm) based on a monolithic resonators. Such resonators utilize birefringent filters formed by YVO4 beam displacer and KTP or YVO4 crystals to force single frequency operation at 532 nm or 1064 nm, respectively. In both configurations Nd:YVO4 gain crystal is used. The resonators dimensions are 1x1x10.5 mm3 and 1x1x8.5 mm3 for green and infrared configurations, respectively. Presented laser devices, with total dimensions of 40x52x120 mm3, are fully equipped with driving electronics, pump diode, optical and mechanical components. The highly integrated (36x15x65 mm3) low noise driving electronics with implemented digital PID controller was designed. It provides pump current and resonator temperature stability of ±30 μA@650 mA and ±0,003ºC, respectively. The laser parameters can be set and monitored via the USB interface by external application. The developed laser construction is universal. Hence, the other wavelengths can be obtained only by replacing the monolithic resonator. The optical output powers in single frequency regime was at the level of 42 mW@532 nm and 0.5 W@1064 nm with the long-term fluctuations of ±0.85 %. The linewidth and the passive frequency stability under the free running conditions were Δν < 100 kHz and 3ṡ10-9@1 s integration time, respectively. The total electrical power supply consumption of laser module was only 4 W. Presented compact, single frequency laser operating at 532 nm and 1064 nm may be used as an excellent source for laser vibrometry, interferometry or seed laser for fiber amplifiers.

Double Fano resonances in plasmon coupling nanorods

International Nuclear Information System (INIS)

Liu, Fei; Jin, Jie

2015-01-01

Fano resonances are investigated in nanorods with symmetric lengths and side-by-side assembly. Single Fano resonance can be obtained by a nanorod dimer, and double Fano resonances are shown in nanorod trimers with side-by-side assembly. With transverse plasmon excitation, Fano resonances are caused by the destructive interference between a bright superradiant mode and dark subradiant modes. The bright mode originates from the electric plasmon resonance, and the dark modes originate from the magnetic resonances induced by near-field inter-rod coupling. Double Fano resonances result from double dark modes at different wavelengths, which are induced and tuned by the asymmetric gaps between the adjacent nanorods. Fano resonances show a high figure of merit and large light extinction in the periodic array of assembled nanorods, which can potentially be used in multiwavelength sensing in the visible and near-infrared regions. (paper)

Design and Analysis of Enhanced Modulation Response in Integrated Coupled Cavities DBR Lasers Using Photon-Photon Resonance

Directory of Open Access Journals (Sweden)

Paolo Bardella

2016-01-01

Full Text Available In the last few decades, various solutions have been proposed to increase the modulation bandwidth and, consequently, the transmission bit-rate of semiconductor lasers. In this manuscript, we discuss a design procedure for a recently proposed laser cavity realized with the monolithic integration of two distributed Bragg reflector (DBR lasers allowing one to extend the modulation bandwidth. Such an extension is obtained introducing in the dynamic response a photon-photon resonance (PPR at a frequency higher than the modulation bandwidth of the corresponding single-section laser. Design guidelines will be proposed, and dynamic small and large signal simulations results, calculated using a finite difference traveling wave (FDTW numerical simulator, will be discussed to confirm the design results. The effectiveness of the design procedure is verified in a structure with PPR frequency at 35 GHz allowing one to obtain an open eye diagram for a non-return-to-zero (NRZ digital signal up to 80 GHz . Furthermore, the investigation of the rich dynamics of this structure shows that with proper bias conditions, it is possible to obtain also a tunable self-pulsating signal in a frequency range related to the PPR design.

Laser of optical fiber composed by two coupled cavities: application as optical fiber sensor; Laser de fibra optica compuesto por dos cavidades acopladas: aplicacion como sensor de fibra optica

Energy Technology Data Exchange (ETDEWEB)

Vazquez S, R.A.; Kuzin, E.A.; Ibarra E, B. [Instituto Nacional de Astrofisica, Optica y Electronica (INAOE), A.P. 51 y 216, 72000 Puebla (Mexico); May A, M. [Universidad Autonoma del Carmen (UNACAR) Av. 56 No. 4 por Av. Concordia, Campeche (Mexico); Shlyagin, M.; Marquez B, I. [Centro de Investigacion Cientifica y de Ensenanza Superior de Ensenada (CICESE), 22860 Ensenada, Baja California (Mexico)]. e-mail: ravsa100@hotmail.com

2004-07-01

We show an optical fiber laser sensor which consist of two cavities coupled and three fiber Bragg gratings. We used one Bragg grating (called reference) and two Bragg gratings (called sensors), which have the lower reflection wavelength. The reference grating with the two sensors grating make two cavities: first one is the internal cavity which has 4230 m of length and the another one is the external cavity which has 4277 m of length. Measuring the laser beating frequency for a resonance cavity and moving the frequency peaks when the another cavity is put in resonance, we prove that the arrangement can be used as a two points sensor for determining the difference of temperature or stress between these two points. (Author)

Theoretical analysis of a novel ultrasound generator on an optical fiber tip

Science.gov (United States)

Wu, Nan; Wang, Wenhui; Tian, Ye; Guthy, Charles; Wang, Xingwei

2010-04-01

A novel ultrasound generator consisting of a single mode optical fiber with a layer of gold nanoparticles on its tip has been designed. The generator utilizes the optical and photo-acoustic properties of gold nanoparticles. When heated by laser pulses, a thin absorption layer made up of these nanoparticles at the cleaved surface of a single mode fiber generates a mechanical shock wave caused by thermal expansion. Mie's theory was applied in a MATLAB simulation to determine the relationship between the absorption efficiency and the optical resonance wavelengths of a layer of gold nanospheres. Results showed that the absorption efficiency and related resonance wavelengths of gold nanospheres varied based on the size of the gold nanosphere particles. In order to obtain the bandwidths associated with ultrasound, another MATLAB simulation was run to study the relationship between the power of the laser being used, the size of the gold nanosphere, and the energy decay time. The results of this and the previous simulation showed that the energy decay time is picoseconds in length.

Multi-frequency modes in superconducting resonators: Bridging frequency gaps in off-resonant couplings

Science.gov (United States)

Andersen, Christian Kraglund; Mølmer, Klaus

2015-03-01

A SQUID inserted in a superconducting waveguide resonator imposes current and voltage boundary conditions that makes it suitable as a tuning element for the resonator modes. If such a SQUID element is subject to a periodically varying magnetic flux, the resonator modes acquire frequency side bands. We calculate the multi-frequency eigenmodes and these can couple resonantly to physical systems with different transition frequencies and this makes the resonator an efficient quantum bus for state transfer and coherent quantum operations in hybrid quantum systems. As an example of the application, we determine their coupling to transmon qubits with different frequencies and we present a bi-chromatic scheme for entanglement and gate operations. In this calculation, we obtain a maximally entangled state with a fidelity F = 95 % . Our proposal is competitive with the achievements of other entanglement-gates with superconducting devices and it may offer some advantages: (i) There is no need for additional control lines and dephasing associated with the conventional frequency tuning of qubits. (ii) When our qubits are idle, they are far detuned with respect to each other and to the resonator, and hence they are immune to cross talk and Purcell-enhanced decay.

Sensing performance analysis on Fano resonance of metallic double-baffle contained MDM waveguide coupled ring resonator

Science.gov (United States)

Chen, Ying; Luo, Pei; Liu, Xiaofei; Di, Yuanjian; Han, Shuaitao; Cui, Xingning; He, Lei

2018-05-01

Based on the transmission property and the photon localization characteristic of the surface plasmonic sub-wavelength structure, a metallic double-baffle contained metal-dielectric-metal (MDM) waveguide coupled ring resonator is proposed. Like the electromagnetically induced transparency (EIT), the Fano resonance can be achieved by the interference between the metallic double-baffle resonator and the ring resonator. Based on the coupled mode theory, the transmission property is analyzed. Through the numerical simulation by the finite element method (FEM), the quantitative analysis on the influences of the radius R of the ring and the coupling distance g between the metallic double-baffle resonator and the ring resonator for the figure of merit (FOM) is performed. And after the structure parameter optimization, the sensing performance of the waveguide structure is discussed. The simulation results show that the FOM value of the optimized structure can attain to 5.74 ×104 and the sensitivity of resonance wavelength with refractive index drift is about 825 nm/RIU. The range of the detected refractive index is suitable for all gases. The waveguide structure can provide effective theoretical references for the design of integrated plasmonic devices.

Coupled Photonic Crystal Cavity Array Laser

DEFF Research Database (Denmark)

Schubert, Martin

in the quadratic lattice. Processing techniques are developed and optimized in order fabricate photonic crystals membranes in gallium arsenide with quantum dots as gain medium and in indium gallium arsenide phosphide with quantum wells as gain medium. Several key issues in process to ensure good quality....... The results are in good agreement with standard coupled mode theory. Also a novel type of photonic crystal structure is proposed called lambda shifted cavity which is a twodimensional photonic crystal laser analog of a VCSEL laser. Detailed measurements of the coupled modes in the photonic crystals...... with quantum dots are carried out. In agreement with a simple gain model the structures do not show stimulated emission. The spectral splitting due to the coupling between single cavities as well as arrays of cavities is studied theoretically and experimentally. Lasing is observed for photonic crystal cavity...

Rf transfer in the Coupled-Cavity Free-Electron Laser Two-Beam Accelerator

International Nuclear Information System (INIS)

Makowski, M.A.

1991-01-01

A significant technical problem associated with the Coupled-Cavity Free-Electron Laser Two-Beam Accelerator is the transfer of RF energy from the drive accelerator to the high-gradient accelerator. Several concepts have been advanced to solve this problem. This paper examines one possible solution in which the drive and high-gradient cavities are directly coupled to one another by means of holes in the cavity walls or coupled indirectly through a third intermediate transfer cavity. Energy cascades through the cavities on a beat frequency time scale which must be made small compared to the cavity skin time but large compared to the FEL pulse length. The transfer is complicated by the fact that each of the cavities in the system can support many resonant modes near the chosen frequency of operation. A generalized set of coupled-cavity equations has been developed to model the energy transfer between the various modes in each of the cavities. For a two cavity case transfer efficiencies in excess of 95% can be achieved. 3 refs., 2 figs

Gas breakdown at cyclotron resonance with a submillimeter laser

International Nuclear Information System (INIS)

Hacker, M.P.; Temkin, R.J.; Lax, B.

1976-01-01

A pulsed 496-μm CH 3 F laser is used to produce gas breakdown in He at pressures between 1 and 300 Torr in an intense longitudinal magnetic field. Breakdown is detected by the observation of visible light when the electron cyclotron frequency (eB/m) equals the laser frequency, which occurs at B=216 kG for lambda=496 μm. At the lowest helium pressures and near cyclotron resonance, the focused laser intensity of 40 kW/cm 2 gives rise to very large electron heating rates, well beyond the limit of validity of conventional equilibrium breakdown theory. The observed result is an intensity-dependent resonant linewidth, much larger than predicted by equilibrium theories

UV Resonant Raman Spectrometer with Multi-Line Laser Excitation

Science.gov (United States)

Lambert, James L.; Kohel, James M.; Kirby, James P.; Morookian, John Michael; Pelletier, Michael J.

2013-01-01

A Raman spectrometer employs two or more UV (ultraviolet) laser wavel engths to generate UV resonant Raman (UVRR) spectra in organic sampl es. Resonant Raman scattering results when the laser excitation is n ear an electronic transition of a molecule, and the enhancement of R aman signals can be several orders of magnitude. In addition, the Ra man cross-section is inversely proportional to the fourth power of t he wavelength, so the UV Raman emission is increased by another fact or of 16, or greater, over visible Raman emissions. The Raman-scatter ed light is collected using a high-resolution broadband spectrograph . Further suppression of the Rayleigh-scattered laser light is provi ded by custom UV notch filters.

Mode coupling in terahertz metamaterials using sub-radiative and super-radiative resonators

International Nuclear Information System (INIS)

Qiao, Shen; Zhang, Yaxin; Zhao, Yuncheng; Xu, Gaiqi; Sun, Han; Yang, Ziqiang; Liang, Shixiong

2015-01-01

We theoretically and experimentally explored the electromagnetically induced transparency (EIT) mode-coupling in terahertz (THz) metamaterial resonators, in which a dipole resonator with a super-radiative mode is coupled to an inductance-capacitance resonator with a sub-radiative mode. The interference between these two resonators depends on the relative spacing between them, resulting in a tunable transparency window in the absorption spectrum. Mode coupling was experimentally demonstrated for three spacing dependent EIT metamaterials. Transmittance of the transparency windows could be either enhanced or suppressed, producing different spectral linewidths. These spacing dependent mode-coupling metamaterials provide alternative ways to create THz devices, such as filters, absorbers, modulators, sensors, and slow-light devices

Modeling laser brightness from cross Porro prism resonators

Science.gov (United States)

Forbes, Andrew; Burger, Liesl; Litvin, Igor Anatolievich

2006-08-01

Laser brightness is a parameter often used to compare high power laser beam delivery from various sources, and incorporates both the power contained in the particular mode, as well as the propagation of that mode through the beam quality factor, M2. In this study a cross Porro prism resonator is considered; crossed Porro prism resonators have been known for some time, but until recently have not been modeled as a complete physical optics system that allows the modal output to be determined as a function of the rotation angle of the prisms. In this paper we consider the diffraction losses as a function of the prism rotation angle relative to one another, and combine this with the propagation of the specific modes to determine the laser output brightness as a function of the prism orientation.

Application of laser resonance scattering to the study of high-temperature plasma-wall interaction

International Nuclear Information System (INIS)

Maeda, Mitsuo; Muraoka, Katsunori; Hamamoto, Makoto; Akazaki, Masanori; Miyazoe, Yasushi

1981-01-01

Studies on laser resonance scattering and its application to the study of high-temperature plasma-wall interaction are reviewed. The application of dye laser beam to resonant scattering method has been developed. This method is able to detect low density atoms. The fluorescent photon counts can be estimated for a two-level system and a three-level system. The S/N ratio, Which is in close connection with the detection limit, has been estimated. The doppler effect due to the thermal motion of atoms is taken into consideration. The calibration of the absolute number of atoms is necessary. Tunable coherent light is used as the light source for resonance scattering method. This is able to excite atoms strongly and to increase the detection efficiency. As dye lasers, a N 2 laser, a YAG laser, and a KrF excimer laser have been studied. In VUV region, rare gas or rare gas halide lasers can be used. The strong output power can be expected when the resonance lines of atoms meet the synchronizing region of the excimer laser. The resonance scattering method is applied to the detection of impurity metal atoms in plasma. The studies of laser systems for the detection of hydrogen atoms are also in progress. (Kato, T.)

Design of high power solid-state pulsed laser resonators

International Nuclear Information System (INIS)

Narro, R.; Ponce, L.; Arronte, M.

2009-01-01

Methods and configurations for the design of high power solid-state pulsed laser resonators, operating in free running, are presented. For fundamental mode high power resonators, a method is proposed for the design of a resonator with joined stability zones. In the case of multimode resonators, two configurations are introduced for maximizing the laser overall efficiency due to the compensation of the astigmatism induced by the excitation. The first configuration consists in a triangular ring resonator. The results for this configuration are discussed theoretically, showing that it is possible to compensate the astigmatism of the thermal lens virtually in a 100%; however this is only possible for a specific pumping power. The second configuration proposes a dual-active medium resonator, rotated 90 degree one from the other around the optical axis, where each active medium acts as an astigmatic lens of the same dioptric power. The reliability of this configuration is corroborated experimentally using a Nd:YAG dual-active medium resonator. It is found that in the pumping power range where the astigmatism compensation is possible, the overall efficiency is constant, even when increasing the excitation power with the consequent increase of the thermal lens dioptric power. (Author)

Equilibrium beam distribution in an electron storage ring near linear synchrobetatron coupling resonances

Directory of Open Access Journals (Sweden)

Boaz Nash

2006-03-01

Full Text Available Linear dynamics in a storage ring can be described by the one-turn map matrix. In the case of a resonance where two of the eigenvalues of this matrix are degenerate, a coupling perturbation causes a mixing of the uncoupled eigenvectors. A perturbation formalism is developed to find eigenvalues and eigenvectors of the one-turn map near such a linear resonance. Damping and diffusion due to synchrotron radiation can be obtained by integrating their effects over one turn, and the coupled eigenvectors can be used to find the coupled damping and diffusion coefficients. Expressions for the coupled equilibrium emittances and beam distribution moments are then derived. In addition to the conventional instabilities at the sum, integer, and half-integer resonances, it is found that the coupling can cause an instability through antidamping near a sum resonance even when the symplectic dynamics are stable. As one application of this formalism, the case of linear synchrobetatron coupling is analyzed where the coupling is caused by dispersion in the rf cavity, or by a crab cavity. Explicit closed-form expressions for the sum/difference resonances are given along with the integer/half-integer resonances. The integer and half-integer resonances caused by coupling require particular care. We find an example of this with the case of a crab cavity for the integer resonance of the synchrotron tune. Whether or not there is an instability is determined by the value of the horizontal betatron tune, a unique feature of these coupling-caused integer or half-integer resonances. Finally, the coupled damping and diffusion coefficients along with the equilibrium invariants and projected emittances are plotted as a function of the betatron and synchrotron tunes for an example storage ring based on PEP-II.

Control of ring lasers by means of coupled cavities

DEFF Research Database (Denmark)

Buchhave, Preben; Abitan, Haim; Tidemand-Lichtenberg, Peter

2000-01-01

Variable phase coupling to an external ring is used to control a unidirectional ring laser. The observed behavior of the coupled rings is explained theoretically. We have found experimentally that by quickly changing the phase of the feedback from the external ring it is possible to Q......-switch the ring laser. Also, at certain values of the phase of the feedback in the external ring, instabilities in the total system occur and oscillations arise in the ring laser....

Quantum heat engine with coupled superconducting resonators

Science.gov (United States)

Hardal, Ali Ü. C.; Aslan, Nur; Wilson, C. M.; Müstecaplıoǧlu, Özgür E.

2017-12-01

We propose a quantum heat engine composed of two superconducting transmission line resonators interacting with each other via an optomechanical-like coupling. One resonator is periodically excited by a thermal pump. The incoherently driven resonator induces coherent oscillations in the other one due to the coupling. A limit cycle, indicating finite power output, emerges in the thermodynamical phase space. The system implements an all-electrical analog of a photonic piston. Instead of mechanical motion, the power output is obtained as a coherent electrical charging in our case. We explore the differences between the quantum and classical descriptions of our system by solving the quantum master equation and classical Langevin equations. Specifically, we calculate the mean number of excitations, second-order coherence, as well as the entropy, temperature, power, and mean energy to reveal the signatures of quantum behavior in the statistical and thermodynamic properties of the system. We find evidence of a quantum enhancement in the power output of the engine at low temperatures.

Modeling of Coupled Nano-Cavity Lasers

DEFF Research Database (Denmark)

Skovgård, Troels Suhr

-of-states and it is argued that Purcell enhancement should also be included in stimulated recombination term, contrary to the common practice in the literature. It is shown that for quantum well devices, the Purcell enhancement is effectively independent of the cavity quality factor due to the broad electronic density......-of-states relative to the optical density-of-states. The low effective Purcell eect for quantum well devices limits the highest possible modulation bandwidth to a few tens of gigahertz, which is comparable to the performance of conventional diode lasers. Compared to quantum well devices, quantum dot devices have...... is useful for design of coupled systems. A tight-binding description for coupled nanocavity lasers is developed and employed to investigate the phase-locking behavior for the system of two coupled cavities. Phase-locking is found to be critically dependent on exact parameter values and to be dicult...

A high-power diode-laser-pumped CW Nd:YAG laser using a stable-unstable resonator

International Nuclear Information System (INIS)

Mudge, M.; Ostermeyer, P.; Veitch, J.; Munch, J.; Hamilton, M.W.

2000-01-01

Full text: The design and operation of a power-scalable diode-laser-pumped CW Nd:YAG zigzag slab laser that uses a stable-unstable resonator with a graded reflectivity mirror as an output coupler is described. We demonstrate control of the thermal lens strength in the unstable plane and weak thermal lensing in the stable plane that is independent of pump power, vital for efficient scalability. This enabled CW operation of the stable-unstable resonator with excellent near- and far-field beam quality

Elastic properties of gamma-Pu by resonant ultrasound spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Migliori, Albert [Los Alamos National Laboratory; Betts, J [Los Alamos National Laboratory; Trugman, A [Los Alamos National Laboratory; Mielke, C H [Los Alamos National Laboratory; Mitchell, J N [Los Alamos National Laboratory; Ramos, M [Los Alamos National Laboratory; Stroe, I [WORXESTER, MA

2009-01-01

Despite intense experimental and theoretical work on Pu, there is still little understanding of the strange properties of this metal. We used resonant ultrasound spectroscopy method to investigate the elastic properties of pure polycrystalline Pu at high temperatures. Shear and longitudinal elastic moduli of the {gamma}-phase of Pu were determined simultaneously and the bulk modulus was computed from them. A smooth linear and large decrease of all elastic moduli with increasing temperature was observed. We calculated the Poisson ratio and found that it increases from 0.242 at 519K to 0.252 at 571K.

Silicon-Nitride-based Integrated Optofluidic Biochemical Sensors using a Coupled-Resonator Optical Waveguide

Directory of Open Access Journals (Sweden)

Jiawei eWANG

2015-04-01

Full Text Available Silicon nitride (SiN is a promising material platform for integrating photonic components and microfluidic channels on a chip for label-free, optical biochemical sensing applications in the visible to near-infrared wavelengths. The chip-scale SiN-based optofluidic sensors can be compact due to a relatively high refractive index contrast between SiN and the fluidic medium, and low-cost due to the complementary metal-oxide-semiconductor (CMOS-compatible fabrication process. Here, we demonstrate SiN-based integrated optofluidic biochemical sensors using a coupled-resonator optical waveguide (CROW in the visible wavelengths. The working principle is based on imaging in the far field the out-of-plane elastic-light-scattering patterns of the CROW sensor at a fixed probe wavelength. We correlate the imaged pattern with reference patterns at the CROW eigenstates. Our sensing algorithm maps the correlation coefficients of the imaged pattern with a library of calibrated correlation coefficients to extract a minute change in the cladding refractive index. Given a calibrated CROW, our sensing mechanism in the spatial domain only requires a fixed-wavelength laser in the visible wavelengths as a light source, with the probe wavelength located within the CROW transmission band, and a silicon digital charge-coupled device (CCD / CMOS camera for recording the light scattering patterns. This is in sharp contrast with the conventional optical microcavity-based sensing methods that impose a strict requirement of spectral alignment with a high-quality cavity resonance using a wavelength-tunable laser. Our experimental results using a SiN CROW sensor with eight coupled microrings in the 680nm wavelength reveal a cladding refractive index change of ~1.3 × 10^-4 refractive index unit (RIU, with an average sensitivity of ~281 ± 271 RIU-1 and a noise-equivalent detection limit (NEDL of 1.8 ×10^-8 RIU ~ 1.0 ×10^-4 RIU across the CROW bandwidth of ~1 nm.

Zero Cross-Talk Regimes in Dually Modulated Mutually-Coupled Nano-lasers

International Nuclear Information System (INIS)

Han, H; Zhang, M J; Wang, Y C; Shore, K A

2017-01-01

The modulation properties of dually modulated mutually-coupled nano-lasers have been analyzed using rate equations which include the Purcell cavity-enhanced spontaneous emission factor F and the spontaneous emission coupling factor β . Analysis of the dynamical response of modulated mutually-coupled nano-lasers reveals the existence of regimes of zero cross-talk wherein the response of one nano-laser is not impacted by the dynamics of the other nano-laser. The availability of zero-cross talk regimes is seen to offer opportunities for exploitation in photonic integrated circuits. (paper)

Coupling of high-quality-factor optical resonators

International Nuclear Information System (INIS)

Salzenstein, Patrice; Henriet, Rémi; Coillet, Aurélien; Chembo, Yanne K; Mortier, Michel; Sérier-Brault, Hélène; Rasoloniaina, Alphonse; Dumeige, Yannick; Féron, Patrice

2013-01-01

We improve theoretically and experimentally the problem of the coupling between a high Q-factor resonator and its external coupler. We have observed oscillations of ringing induced by the sweeping of the excitation frequency of an active microsphere. Thanks to this approach, the quality factor of an optical resonator was measured and we obtained Q = 5.8 × 10 8 . (paper)

Semiconductor ring lasers coupled by a single waveguide

Science.gov (United States)

Coomans, W.; Gelens, L.; Van der Sande, G.; Mezosi, G.; Sorel, M.; Danckaert, J.; Verschaffelt, G.

2012-06-01

We experimentally and theoretically study the characteristics of semiconductor ring lasers bidirectionally coupled by a single bus waveguide. This configuration has, e.g., been suggested for use as an optical memory and as an optical neural network motif. The main results are that the coupling can destabilize the state in which both rings lase in the same direction, and it brings to life a state with equal powers at both outputs. These are both undesirable for optical memory operation. Although the coupling between the rings is bidirectional, the destabilization occurs due to behavior similar to an optically injected laser system.

Magnetic resonance thermometry for monitoring photothermal effects of interstitial laser irradiation

Science.gov (United States)

Goddard, Jessica; Jose, Jessnie; Figueroa, Daniel; Le, Kelvin; Liu, Hong; Nordquist, Robert E.; Hode, Tomas; Chen, Wei R.

2012-03-01

Selective photothermal interaction using dye-assisted non-invasive laser irradiation has limitations when treating deeper tumors or when the overlying skin is heavily pigmented. We developed an interstitial laser irradiation method to induce the desired photothermal effects. An 805-nm near-infrared laser with a cylindrical diffuser was used to treat rat mammary tumors by placing the active tip of the fiber inside the target tumors. Three different power settings (1.0 to 1.5 watts) were applied to treat animal tumors with an irradiation duration of 10 minutes. The temperature distributions of the treated tumors were measured by a 7.1-Tesla magnetic resonance imager using proton resonance frequency (PRF) method. Three-dimensional temperature profiles were reconstructed and assessed using PRF. This is the first time a 7.1-Tesla magnetic resonance imager has been used to monitor interstitial laser irradiation via PRF. This study provides a basic understanding of the photothermal interaction needed to control the thermal damage inside tumor using interstitial laser irradiation. It also shows that PRF can be used effectively in monitoring photothermal interaction. Our long-term goal is to develop a PRF-guided laser therapy for cancer treatment.

Experiments on resonantly photo-pumped x-ray lasers

International Nuclear Information System (INIS)

Nilsen, J.; Porter, J.L.; Da Silva, L.B.; MacGowan, B.; Beiersdorfer, P..; Elliott, S.R.; Young, B.K.

1992-01-01

We describe our recent effort to identify and study a promising resonantly photopumped x-ray laser scheme. In particular we will describe a scheme which uses the strong emission lines of a nickel-like ion to resonantly photo-pump a neon-like ion and enhance the lasing of the neon-like 3p → 3s transitions

Increase in effectiveness of low frequency acoustic liners by use of coupled Helmholtz resonators

Science.gov (United States)

Dean, L. W.

1977-01-01

Coupling of Helmholtz resonators in a low-frequency absorber array was studied as a means for increasing the effectiveness for absorbing low-frequency core engine noise. The equations for the impedance of the coupled-resonator systems were developed in terms of uncoupled-resonator parameters, and the predicted impedance for a parallel-coupled scheme is shown to compare favorably with measurements from a test model. In addition, attenuation measurements made in a flow duct on test coupled-resonator panels are shown to compare favorably with predicted values. Finally, the parallel-coupled concept is shown to give significantly more attenuation than that of a typical uncoupled resonator array of the same total volume.

Transversely coupled Fabry-Perot resonators with Bragg grating reflectors.

Science.gov (United States)

Saber, Md Ghulam; Wang, Yun; El-Fiky, Eslam; Patel, David; Shahriar, Kh Arif; Alam, Md Samiul; Jacques, Maxime; Xing, Zhenping; Xu, Luhua; Abadía, Nicolás; Plant, David V

2018-01-01

We design and demonstrate Fabry-Perot resonators with transverse coupling using Bragg gratings as reflectors on the silicon-on-insulator (SOI) platform. The effects of tailoring the cavity length and the coupling coefficient of the directional coupler on the spectral characteristics of the device are studied. The fabricated resonators achieved an extinction ratio (ER) of 37.28 dB and a Q-factor of 3356 with an effective cavity length of 110 μm, and an ER of 8.69 dB and a Q-factor of 23642 with a 943 μm effective cavity length. The resonator structure presented here has the highest reported ER on SOI and provides additional degrees of freedom compared to an all-pass ring resonator to tune the spectral characteristics.

Parameters optimization for magnetic resonance coupling wireless power transmission.

Science.gov (United States)

Li, Changsheng; Zhang, He; Jiang, Xiaohua

2014-01-01

Taking maximum power transmission and power stable transmission as research objectives, optimal design for the wireless power transmission system based on magnetic resonance coupling is carried out in this paper. Firstly, based on the mutual coupling model, mathematical expressions of optimal coupling coefficients for the maximum power transmission target are deduced. Whereafter, methods of enhancing power transmission stability based on parameters optimal design are investigated. It is found that the sensitivity of the load power to the transmission parameters can be reduced and the power transmission stability can be enhanced by improving the system resonance frequency or coupling coefficient between the driving/pick-up coil and the transmission/receiving coil. Experiment results are well conformed to the theoretical analysis conclusions.

Resonant Photonic States in Coupled Heterostructure Photonic Crystal Waveguides

Directory of Open Access Journals (Sweden)

Sabarinathan J

2010-01-01

Full Text Available Abstract In this paper, we study the photonic resonance states and transmission spectra of coupled waveguides made from heterostructure photonic crystals. We consider photonic crystal waveguides made from three photonic crystals A, B and C, where the waveguide heterostructure is denoted as B/A/C/A/B. Due to the band structure engineering, light is confined within crystal A, which thus act as waveguides. Here, photonic crystal C is taken as a nonlinear photonic crystal, which has a band gap that may be modified by applying a pump laser. We have found that the number of bound states within the waveguides depends on the width and well depth of photonic crystal A. It has also been found that when both waveguides are far away from each other, the energies of bound photons in each of the waveguides are degenerate. However, when they are brought close to each other, the degeneracy of the bound states is removed due to the coupling between them, which causes these states to split into pairs. We have also investigated the effect of the pump field on photonic crystal C. We have shown that by applying a pump field, the system may be switched between a double waveguide to a single waveguide, which effectively turns on or off the coupling between degenerate states. This reveals interesting results that can be applied to develop new types of nanophotonic devices such as nano-switches and nano-transistors.

Significance of the Resonance Condition for Controlling the Seam Position in Laser-assisted TIG Welding

Science.gov (United States)

Emde, B.; Huse, M.; Hermsdorf, J.; Kaierle, S.; Wesling, V.; Overmeyer, L.; Kozakov, R.; Uhrlandt, D.

As an energy-preserving variant of laser hybrid welding, laser-assisted arc welding uses laser powers of less than 1 kW. Recent studies have shown that the electrical conductivity of a TIG welding arc changes within the arc in case of a resonant interaction between laser radiation and argon atoms. This paper presents investigations on how to control the position of the arc root on the workpiece by means of the resonant interaction. Furthermore, the influence on the welding result is demonstrated. The welding tests were carried out on a cooled copper plate and steel samples with resonant and non-resonant laser radiation. Moreover, an analysis of the weld seam is presented.

The calculation of Feshbach resonances using coupled propagator equations

International Nuclear Information System (INIS)

Zhan, Hongbin; Zhang, Yinchun; Winkler, P.

1994-01-01

A coupled channel theory of resonances has been formulated within the propagator approach of man-body theory and applied to the 1s3s 2 resonance of e-helium scattering. This system has previously been studied both experimentally and theoretically. These results for the width of the resonance agree well with these earlier findings

Resonance ionization laser ion sources for on-line isotope separators (invited)

International Nuclear Information System (INIS)

Marsh, B. A.

2014-01-01

A Resonance Ionization Laser Ion Source (RILIS) is today considered an essential component of the majority of Isotope Separator On Line (ISOL) facilities; there are seven laser ion sources currently operational at ISOL facilities worldwide and several more are under development. The ionization mechanism is a highly element selective multi-step resonance photo-absorption process that requires a specifically tailored laser configuration for each chemical element. For some isotopes, isomer selective ionization may even be achieved by exploiting the differences in hyperfine structures of an atomic transition for different nuclear spin states. For many radioactive ion beam experiments, laser resonance ionization is the only means of achieving an acceptable level of beam purity without compromising isotope yield. Furthermore, by performing element selection at the location of the ion source, the propagation of unwanted radioactivity downstream of the target assembly is reduced. Whilst advances in laser technology have improved the performance and reliability of laser ion sources and broadened the range of suitable commercially available laser systems, many recent developments have focused rather on the laser/atom interaction region in the quest for increased selectivity and/or improved spectral resolution. Much of the progress in this area has been achieved by decoupling the laser ionization from competing ionization processes through the use of a laser/atom interaction region that is physically separated from the target chamber. A new application of gas catcher laser ion source technology promises to expand the capabilities of projectile fragmentation facilities through the conversion of otherwise discarded reaction fragments into high-purity low-energy ion beams. A summary of recent RILIS developments and the current status of laser ion sources worldwide is presented

Extremely high-brightness kW-class fiber coupled diode lasers with wavelength stabilization

Science.gov (United States)

Huang, Robin K.; Chann, Bien; Glenn, John D.

2011-06-01

TeraDiode has produced ultra-high brightness fiber-coupled direct diode lasers. A fiber-coupled direct diode laser with a power level of 1,040 W from a 200 μm core diameter, 0.18 numerical aperture (NA) output fiber at a single center wavelength was demonstrated. This was achieved with a novel beam combining and shaping technique using COTS diode lasers. The fiber-coupled output corresponds to a Beam Parameter Product (BPP) of 18 mm-mrad and is the lowest BPP kW-class direct diode laser yet reported. The laser has been used to demonstrate laser cutting and welding of steel sheet metal up to 6.65 mm thick. Higher brightness fiber-coupled diode lasers, including a module with 418 W of power coupled to a 100 μm, 0.15 NA fiber, have also been demonstrated.

Time-resolved spectroscopy and fluorescence resonance energy transfer in the study of excimer laser damage of chromatin

Energy Technology Data Exchange (ETDEWEB)

Radu, L. [Department of Molecular Genetics and Radiobiology, Babes National Institute, Bucharest (Romania)], E-mail: lilianajradu@yahoo.fr; Mihailescu, I. [Department of Lasers, Laser, Plasma and Radiation Physics Institute, Bucharest (Romania); Radu, S. [Department of Computer Science, Polytechnics University, Bucharest (Romania); Gazdaru, D. [Department of Biophysics, Bucharest University (Romania)

2007-09-21

The analysis of chromatin damage produced by a 248 nm excimer laser radiation, for doses of 0.3-3 MJ/m{sup 2} was carried out by time-resolved spectroscopy and fluorescence resonance energy transfer (FRET). The chromatin was extracted from a normal and a tumoral tissue of Wistar rats. The decrease with laser dose of the relative contribution of the excited state lifetimes of ethidium bromide (EtBr) bounded to chromatin constitutes an evidence of the reduction of chromatin deoxyribonucleic acid (DNA) double-strand structure. FRET was performed from dansyl chloride to acridine orange, both coupled to chromatin. The increase of the average distance between these ligands, under the action of laser radiation, reflects a loosening of the chromatin structure. The radiosensitivity of tumor tissue chromatin is higher than that of a normal tissue. The determination of the chromatin structure modification in an excimer laser field can be of interest in laser therapy.

Time-resolved spectroscopy and fluorescence resonance energy transfer in the study of excimer laser damage of chromatin

International Nuclear Information System (INIS)

Radu, L.; Mihailescu, I.; Radu, S.; Gazdaru, D.

2007-01-01

The analysis of chromatin damage produced by a 248 nm excimer laser radiation, for doses of 0.3-3 MJ/m 2 was carried out by time-resolved spectroscopy and fluorescence resonance energy transfer (FRET). The chromatin was extracted from a normal and a tumoral tissue of Wistar rats. The decrease with laser dose of the relative contribution of the excited state lifetimes of ethidium bromide (EtBr) bounded to chromatin constitutes an evidence of the reduction of chromatin deoxyribonucleic acid (DNA) double-strand structure. FRET was performed from dansyl chloride to acridine orange, both coupled to chromatin. The increase of the average distance between these ligands, under the action of laser radiation, reflects a loosening of the chromatin structure. The radiosensitivity of tumor tissue chromatin is higher than that of a normal tissue. The determination of the chromatin structure modification in an excimer laser field can be of interest in laser therapy

Degradation of edible oil during food processing by ultrasound: electron paramagnetic resonance, physicochemical, and sensory appreciation.

Science.gov (United States)

Pingret, Daniella; Durand, Grégory; Fabiano-Tixier, Anne-Sylvie; Rockenbauer, Antal; Ginies, Christian; Chemat, Farid

2012-08-08

During ultrasound processing of lipid-containing food, some off-flavors can be detected, which can incite depreciation by consumers. The impacts of ultrasound treatment on sunflower oil using two different ultrasound horns (titanium and pyrex) were evaluated. An electron paramagnetic resonance study was performed to identify and quantify the formed radicals, along with the assessment of classical physicochemical parameters such as peroxide value, acid value, anisidine value, conjugated dienes, polar compounds, water content, polymer quantification, fatty acid composition, and volatiles profile. The study shows an increase of formed radicals in sonicated oils, as well as the modification of physicochemical parameters evidencing an oxidation of treated oils.

Magnetic resonance imaging is often misleading when used as an adjunct to ultrasound in the management of placenta accreta spectrum disorders.

Science.gov (United States)

Einerson, Brett D; Rodriguez, Christina E; Kennedy, Anne M; Woodward, Paula J; Donnelly, Meghan A; Silver, Robert M

2018-06-01

Magnetic resonance imaging is reported to have good sensitivity and specificity in the diagnosis of placenta accreta spectrum disorders, and is often used as an adjunct to ultrasound. But the additional utility of obtaining magnetic resonance imaging to assist in the clinical management of patients with placenta accreta spectrum disorders, above and beyond the information provided by ultrasound, is unknown. We aimed to determine whether magnetic resonance imaging provides data that may inform clinical management by changing the sonographic diagnosis of placenta accreta spectrum disorders. In all, 78 patients with sonographic evidence or clinical suspicion of placenta accreta spectrum underwent magnetic resonance imaging of the abdomen and pelvis in orthogonal planes through the uterus utilizing T1- and T2-weighted imaging sequences at the University of Utah and the University of Colorado from 1997 through 2017. The magnetic resonance imaging was interpreted by radiologists with expertise in diagnosis of placenta accreta spectrum who had knowledge of the sonographic interpretation and clinical risk factors for placenta accreta spectrum disorders. The primary outcome was a change in diagnosis from sonographic interpretation that could alter clinical management, which was defined a priori. Diagnostic accuracy was verified by surgical and histopathologic diagnosis at the time of delivery. A change in diagnosis that could potentially alter clinical management occurred in 28 (36%) cases. Magnetic resonance imaging correctly changed the diagnosis in 15 (19%), and correctly confirmed the diagnosis in 34 (44%), but resulted in an incorrect change in diagnosis in 13 (17%), and an incorrect confirmation of ultrasound diagnosis in 15 (21%). Magnetic resonance imaging was not more likely to change a diagnosis in the 24 cases of posterior and lateral placental location compared to anterior location (33% vs 37%, P = .84). Magnetic resonance imaging resulted in overdiagnosis in

A flexible ultrasound transducer array with micro-machined bulk PZT.

Science.gov (United States)

Wang, Zhe; Xue, Qing-Tang; Chen, Yuan-Quan; Shu, Yi; Tian, He; Yang, Yi; Xie, Dan; Luo, Jian-Wen; Ren, Tian-Ling

2015-01-23

This paper proposes a novel flexible piezoelectric micro-machined ultrasound transducer, which is based on PZT and a polyimide substrate. The transducer is made on the polyimide substrate and packaged with medical polydimethylsiloxane. Instead of etching the PZT ceramic, this paper proposes a method of putting diced PZT blocks into holes on the polyimide which are pre-etched. The device works in d31 mode and the electromechanical coupling factor is 22.25%. Its flexibility, good conformal contacting with skin surfaces and proper resonant frequency make the device suitable for heart imaging. The flexible packaging ultrasound transducer also has a good waterproof performance after hundreds of ultrasonic electric tests in water. It is a promising ultrasound transducer and will be an effective supplementary ultrasound imaging method in the practical applications.

A Flexible Ultrasound Transducer Array with Micro-Machined Bulk PZT

Directory of Open Access Journals (Sweden)

Zhe Wang

2015-01-01

Full Text Available This paper proposes a novel flexible piezoelectric micro-machined ultrasound transducer, which is based on PZT and a polyimide substrate. The transducer is made on the polyimide substrate and packaged with medical polydimethylsiloxane. Instead of etching the PZT ceramic, this paper proposes a method of putting diced PZT blocks into holes on the polyimide which are pre-etched. The device works in d31 mode and the electromechanical coupling factor is 22.25%. Its flexibility, good conformal contacting with skin surfaces and proper resonant frequency make the device suitable for heart imaging. The flexible packaging ultrasound transducer also has a good waterproof performance after hundreds of ultrasonic electric tests in water. It is a promising ultrasound transducer and will be an effective supplementary ultrasound imaging method in the practical applications.

Fano resonances in a high-Q terahertz whispering-gallery mode resonator coupled to a multi-mode waveguide.

Science.gov (United States)

Vogt, Dominik Walter; Leonhardt, Rainer

2017-11-01

We report on Fano resonances in a high-quality (Q) whispering-gallery mode (WGM) spherical resonator coupled to a multi-mode waveguide in the terahertz (THz) frequency range. The asymmetric line shape and phase of the Fano resonances detected with coherent continuous-wave (CW) THz spectroscopy measurements are in excellent agreement with the analytical model. A very high Q factor of 1600, and a finesse of 22 at critical coupling is observed around 0.35 THz. To the best of our knowledge this is the highest Q factor ever reported for a THz WGM resonator.

Histopathology of breast cancer after magnetic resonance-guided high-intensity focused ultrasound and radiofrequency ablation

NARCIS (Netherlands)

Knuttel, Floor; Waaijer, Laurien; Merckel, LG; van den Bosch, Maurice A A J; Witkamp, Arjen J.; Deckers, Roel; van Diest, Paul J.

AIMS: Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) ablation and radiofrequency ablation (RFA) are being researched as possible substitutes for surgery in breast cancer patients. The histopathological appearance of ablated tissue has not been studied in great detail. This

AISI/DOE Advanced Process Control Program Vol. 4 of 6: ON-LINE, NON-DESTRUCTIVE MECHANICAL PROPERTY MEASUREMENT USING LASER-ULTRASOUND

Energy Technology Data Exchange (ETDEWEB)

Andre' Moreau; Martin Lord; Daniel Levesqure; Marc Dubois; Jean Bussiere; Jean-Pierre Monchalin; Christian Padioleau; Guy Lamouche; Teodor Veres; Martin Viens; Harold Hebert; Pierre Basseras; Cheng-Kuei Jen

2001-03-31

The goal of this project was to demonstrate the feasibility to measure the mechanical properties, such as yield strength, tensile strength, elongation, strain hardening exponent and plastic strain ratio parameters, of low carbon steel sheets on the production line using laser ultrasound. The ultrasound generated by the developed apparatus travels mostly back and forth in the thickness of the steel sheet. By measuring the time delay between two echoes, and the relative amplitude of these two echoes, one can measure ultrasound velocity and attenuation. These are governed by the microstructure: grain size, crystallographic texture, dislocations, etc. Thus, by recording the time behavior of the ultrasonic signal, one can extract microstructural information. These microstructural information together with the modified Hall-Petch equation allow measurement of the mechanical properties. Through laboratory investigations with a laboratory laser ultrasound system, followed by the installation of a prototype system at LTV Steel Company's No.1 Inspection Line in Cleveland, all target mechanical properties of ultra low carbon (ULC), low carbon (LC) and high strength low alloy (HSLA) steel sample lots were measured meeting or nearly meeting all the target accuracies. Thus, the project realized its goal to demonstrate that the mechanical properties of low carbon steel sheets can be measured on-line using laser ultrasound

Manipulating the wavelength-drift of a Tm laser for resonance enhancement in an intra-cavity pumped Ho laser.

Science.gov (United States)

Huang, Haizhou; Huang, Jianhong; Liu, Huagang; Li, Jinhui; Lin, Zixiong; Ge, Yan; Dai, Shutao; Deng, Jing; Lin, Wenxiong

2018-03-05

We demonstrate an enhancement mechanism and thermal model for intra-cavity pumped lasers, where resonance enhancement in intra-cavity pumped Ho laser was achieved by manipulating the wavelength-drift nature of the Tm laser for the first time. Optical conversion efficiency of 37.5% from an absorbed 785 nm diode laser to a Ho laser was obtained with a maximum output power of 7.51 W at 2122 nm, which is comparable to the conversion efficiency in 1.9 μm LD pumped Ho lasers. Meanwhile, more severe thermal effects in the Ho-doped gain medium than the Tm-doped one at high power operation were verified based on the built thermal model. This work benefits the design or evaluation of intra-cavity pumped lasers, and the resonance enhancement originated from the difference in reabsorption loss between stark levels at the lasing manifolds of quasi-three-level rare-earth ions has great interest to improve the existing intra-cavity pumped lasers or explore novel lasers.

Effect of resonance frequency, power input, and saturation gas type on the oxidation efficiency of an ultrasound horn

NARCIS (Netherlands)

Rooze, J.; Rebrov, E.V.; Schouten, J.C.; Keurentjes, J.T.F.

2011-01-01

The sonochemical oxidation efficiency (¿ox) of a commercial titanium alloy ultrasound horn has been measured using potassium iodide as a dosimeter at its main resonance frequency (20 kHz) and two higher resonance frequencies (41 and 62 kHz). Narrow power and frequency ranges have been chosen to

Photon–phonon parametric oscillation induced by quadratic coupling in an optomechanical resonator

International Nuclear Information System (INIS)

Zhang, Lin; Ji, Fengzhou; Zhang, Xu; Zhang, Weiping

2017-01-01

A direct photon–phonon parametric effect of quadratic coupling on the mean-field dynamics of an optomechanical resonator in the large-scale-movement regime is found and investigated. Under a weak pumping power, the mechanical resonator damps to a steady state with a nonlinear static response sensitively modified by the quadratic coupling. When the driving power increases beyond the static energy balance, the steady states lose their stabilities via Hopf bifurcations, and the resonator produces stable self-sustained oscillation (limit-circle behavior) of discrete energies with step-like amplitudes due to the parametric effect of quadratic coupling, which can be understood roughly by the power balance between gain and loss on the resonator. A further increase in the pumping power can induce a chaotic dynamic of the resonator via a typical routine of period-doubling bifurcation, but which can be stabilized by the parametric effect through an inversion-bifurcation process back to the limit-circle states. The bifurcation-to-inverse-bifurcation transitions are numerically verified by the maximal Lyapunov exponents of the dynamics, which indicate an efficient way of suppressing the chaotic behavior of the optomechanical resonator by quadratic coupling. Furthermore, the parametric effect of quadratic coupling on the dynamic transitions of an optomechanical resonator can be conveniently detected or traced by the output power spectrum of the cavity field. (paper)

Stochastic Resonance in a System of Coupled Chaotic Oscillators

International Nuclear Information System (INIS)

Krawiecki, A.

1999-01-01

Noise-free stochastic resonance is investigated numerically in a system of two coupled chaotic Roessler oscillators. Periodic signal is applied either additively or multiplicatively to the coupling term. When the coupling constant is varied the oscillators lose synchronization via attractor bubbling or on-off intermittency. Properly chosen signals are analyzed which reflect the sequence of synchronized (laminar) phases and non-synchronized bursts in the time evolution of the oscillators. Maximum of the signal-to-noise ratio as a function of the coupling constant is observed. Dependence of the signal-to-noise ratio on the frequency of the periodic signal and parameter mismatch between the oscillators is investigated. Possible applications of stochastic resonance in the recovery of signals in secure communication systems based on chaotic synchronization are briefly discussed. (author)

Non-contact optoacoustic imaging with focused air-coupled transducers

Energy Technology Data Exchange (ETDEWEB)

Deán-Ben, X. Luís [Institute for Biological and Medical Imaging (IBMI), Helmholtz Zentrum München, Neuherberg (Germany); Pang, Genny A.; Razansky, Daniel, E-mail: dr@tum.de [Institute for Biological and Medical Imaging (IBMI), Helmholtz Zentrum München, Neuherberg (Germany); School of Medicine, Technische Universität München (TUM), Munich (Germany); Montero de Espinosa, Francisco [CSIC, Institute of Physics and Communication Technologies, Madrid (Spain)

2015-08-03

Non-contact optoacoustic imaging employing raster-scanning of a spherically focused air-coupled ultrasound transducer is showcased herein. Optoacoustic excitation with laser fluence within the maximal permissible human exposure limits in the visible and near-infrared spectra is applied to objects with characteristic dimensions smaller than 1 mm and absorption properties representative of the whole blood at near-infrared wavelengths, and these signals are shown to be detectable without contact to the sample using an air-coupled transducer with reasonable signal averaging. Optoacoustic images of vessel-mimicking tubes embedded in an agar phantom captured with this non-contact sensing technique are also showcased. These initial results indicate that an air-coupled ultrasound detection approach can be suitable for non-contact biomedical imaging with optoacoustics.

Analysis of transmission lines loaded with pairs of coupled resonant elements and application to sensors

International Nuclear Information System (INIS)

Naqui, J.; Su, L.; Mata, J.; Martín, F.

2015-01-01

This paper is focused on the analysis of transmission lines loaded with pairs of magnetically coupled resonators. We have considered two different structures: (i) a microstrip line loaded with pairs of stepped impedance resonators (SIRs), and (ii) a coplanar waveguide (CPW) transmission line loaded with pairs of split ring resonators (SRRs). In both cases, the line exhibits a single resonance frequency (transmission zero) if the resonators are identical (symmetric structure with regard to the line axis), and this resonance is different to the one of the line loaded with a single resonator due to inter-resonator coupling. If the structures are asymmetric, inter-resonator coupling enhances the distance between the two split resonance frequencies that arise. In spite that the considered lines and loading resonators are very different and are described by different lumped element equivalent circuit models, the phenomenology associated to the effects of coupling is exactly the same, and the resonance frequencies are given by identical expressions. The reported lumped element circuit models of both structures are validated by comparing the circuit simulations with extracted parameters with both electromagnetic simulations and experimental data. These structures can be useful for the implementation of microwave sensors based on symmetry properties. - Highlights: • Magnetic-coupling between resonant elements affects transmission properties. • Inter-resonant coupling enhances the distance of two resonant frequencies. • The structures are useful for sensors and comparators, etc

A single-longitudinal-mode Brillouin fiber laser passively stabilized at the pump resonance frequency with a dynamic population inversion grating

International Nuclear Information System (INIS)

Spirin, V V; López-Mercado, C A; Kinet, D; Mégret, P; Fotiadi, A A; Zolotovskiy, I O

2013-01-01

We demonstrate a single-longitudinal-mode Brillouin ring fiber laser passively stabilized at the resonance frequency with a 1.7 m section that is an unpumped polarization-maintaining erbium-doped fiber. The two coupled all-fiber Fabry–Perot interferometers that comprise the cavity, in combination with the dynamical population inversion gratings self-induced in the active fiber, provide adaptive pump-mode selection and Stokes wave generation at the same time. The laser is shown to emit a single-frequency Stokes wave with a linewidth narrower than 100 Hz. (letter)

Effect of polarization and focusing on laser pulse driven auto-resonant particle acceleration

International Nuclear Information System (INIS)

Sagar, Vikram; Sengupta, Sudip; Kaw, Predhiman

2014-01-01

The effect of laser polarization and focusing is theoretically studied on the final energy gain of a particle in the Auto-resonant acceleration scheme using a finite duration laser pulse with Gaussian shaped temporal envelope. The exact expressions for dynamical variables viz. position, momentum, and energy are obtained by analytically solving the relativistic equation of motion describing particle dynamics in the combined field of an elliptically polarized finite duration pulse and homogeneous static axial magnetic field. From the solutions, it is shown that for a given set of laser parameters viz. intensity and pulse length along with static magnetic field, the energy gain by a positively charged particle is maximum for a right circularly polarized laser pulse. Further, a new scheme is proposed for particle acceleration by subjecting it to the combined field of a focused finite duration laser pulse and static axial magnetic field. In this scheme, the particle is initially accelerated by the focused laser field, which drives the non-resonant particle to second stage of acceleration by cyclotron Auto-resonance. The new scheme is found to be efficient over two individual schemes, i.e., auto-resonant acceleration and direct acceleration by focused laser field, as significant particle acceleration can be achieved at one order lesser values of static axial magnetic field and laser intensity

Laser-induced breakdown spectroscopy with laser irradiation resonant with vibrational transitions

International Nuclear Information System (INIS)

Khachatrian, Ani; Dagdigian, Paul J.

2010-01-01

An investigation of laser-induced breakdown spectroscopy (LIBS) of polymers, both in bulk form and spin coated on Si wafers, with laser irradiation in the mid-infrared spectral region is presented. Of particular interest is whether the LIBS signals are enhanced when the laser wavelength is resonant with a fundamental vibrational transition of the polymer. Significant increases in the LIBS signals were observed for irradiation on hydride stretch fundamental transitions, and the magnitude of the enhancement showed a strong dependence on the mode excited. The role of the substrate was investigated by comparison of results for bulk and spin-coated samples. The polymers investigated were Nylon 12 and poly(vinyl alcohol-co-ethylene).

Laser-enhanced high-intensity focused ultrasound heating in an in vivo small animal model

Science.gov (United States)

Jo, Janggun; Yang, Xinmai

2016-11-01

The enhanced heating effect during the combination of high-intensity focused ultrasound (HIFU) and low-optical-fluence laser illumination was investigated by using an in vivo murine animal model. The thighs of murine animals were synergistically irradiated by HIFU and pulsed nano-second laser light. The temperature increases in the target region were measured by a thermocouple under different HIFU pressures, which were 6.2, 7.9, and 9.8 MPa, in combination with 20 mJ/cm2 laser exposures at 532 nm wavelength. In comparison with conventional laser therapies, the laser fluence used here is at least one order of magnitude lower. The results showed that laser illumination could enhance temperature during HIFU applications. Additionally, cavitation activity was enhanced when laser and HIFU irradiation were concurrently used. Further, a theoretical simulation showed that the inertial cavitation threshold was indeed decreased when laser and HIFU irradiation were utilized concurrently.

Coupling effects of resonant and discretized non-resonant continuum states in 4He+6Li scattering at 10 MeV/A

International Nuclear Information System (INIS)

Sinha, T.; Kanungo, R.; Samanta, C.; Ghosh, S.; Basu, P.; Rebel, H.

1996-01-01

Alpha- particle scattering from the resonant (3 + 1 ) and non-resonant continuum states of 6 Li is studied at incident energy 10 MeV/A. The α+d breakup continuum part within the excitation energy E ex = 1.475-2.475 MeV is discretized in two energy bins. Unlike the results at higher incident energies, here the coupled-channel calculations show significant breakup continuum coupling effects on the elastic and inelastic scattering. It is shown that even when the continuum-continuum coupling effects are strong, the experimental data of the ground state and the resonant as well as discretized non-resonant continuum states impose stringent constraint on the coupling strengths of the non-resonant continuum states. (orig.). With 2 figs., 1 tab

MEMS Coupled Resonator for Filter Application in Air

KAUST Repository

Ilyas, Saad; Jaber, Nizar; Younis, Mohammad I.

2017-01-01

We present a mechanically coupled MEMS H resonator capable of performing simultaneous amplification and filter operation in air. The device comprises of two doubly clamped polyimide microbeams joined through the middle by a coupling beam of the same size. The resonator is fabricated via a multilayer surface micromachining process. A special fabrication process and device design is employed to enable the device's operation in air and to achieve mechanical amplification of the output response. Moreover, mixed-frequency excitation is used to demonstrate a tunable wide band filter. The device design combined with the mixed-frequency excitation is used to demonstrate simultaneous amplification and filtering in air.

MEMS Coupled Resonator for Filter Application in Air

KAUST Repository

Ilyas, Saad

2017-11-03

We present a mechanically coupled MEMS H resonator capable of performing simultaneous amplification and filter operation in air. The device comprises of two doubly clamped polyimide microbeams joined through the middle by a coupling beam of the same size. The resonator is fabricated via a multilayer surface micromachining process. A special fabrication process and device design is employed to enable the device\\'s operation in air and to achieve mechanical amplification of the output response. Moreover, mixed-frequency excitation is used to demonstrate a tunable wide band filter. The device design combined with the mixed-frequency excitation is used to demonstrate simultaneous amplification and filtering in air.

Lineshape Engineering in an All-Pass Ring Resonator with Backreflection Coupled to a Symmetrical Fabry-Perot Resonator

KAUST Repository

Melnikov, Vasily

2012-11-10

We derive transfer functions for an all-pass ring resonator with internal backreflection coupled to a symmetrical Fabry-Perot resonator and demonstrate electromagnetically induced transparency-like and Fano-like lineshapes tunable by backreflection in the ring resonator.

Lineshape Engineering in an All-Pass Ring Resonator with Backreflection Coupled to a Symmetrical Fabry-Perot Resonator

KAUST Repository

Melnikov, Vasily; Roqan, Iman S.

2012-01-01

We derive transfer functions for an all-pass ring resonator with internal backreflection coupled to a symmetrical Fabry-Perot resonator and demonstrate electromagnetically induced transparency-like and Fano-like lineshapes tunable by backreflection in the ring resonator.

Laser-material interactions: A study of laser energy coupling with solids

Energy Technology Data Exchange (ETDEWEB)

Shannon, Mark Alan [Univ. of California, Berkeley, CA (United States)

1993-11-01

This study of laser-light interactions with solid materials ranges from low-temperature heating to explosive, plasma-forming reactions. Contained are four works concerning laser-energy coupling: laser (i) heating and (ii) melting monitored using a mirage effect technique, (iii) the mechanical stress-power generated during high-powered laser ablation, and (iv) plasma-shielding. First, a photothermal deflection (PTD) technique is presented for monitoring heat transfer during modulated laser heating of opaque solids that have not undergone phase-change. Of main interest is the physical significance of the shape, magnitude, and phase for the temporal profile of the deflection signal. Considered are the effects that thermophysical properties, boundary conditions, and geometry of the target and optical probe-beam have on the deflection response. PTD is shown to monitor spatial and temporal changes in heat flux leaving the surface due to changes in laser energy coupling. The PTD technique is then extended to detect phase-change at the surface of a solid target. Experimental data shows the onset of melt for indium and tin targets. The conditions for which melt can be detected by PTD is analyzed in terms of geometry, incident power and pulse length, and thermophysical properties of the target and surroundings. Next, monitoring high-powered laser ablation of materials with stress-power is introduced. The motivation for considering stress-power is given, followed by a theoretical discussion of stress-power and how it is determined experimentally. Experiments are presented for the ablation of aluminum targets as a function of energy and intensity. The stress-power response is analyzed for its physical significance. Lastly, the influence of plasma-shielding during high-powered pulsed laser-material interactions is considered. Crater size, emission, and stress-power are measured to determine the role that the gas medium and laser pulse length have on plasma shielding.

Laser-material interactions: A study of laser energy coupling with solids

International Nuclear Information System (INIS)

Shannon, M.A.; California Univ., Berkeley, CA

1993-11-01

This study of laser-light interactions with solid materials ranges from low-temperature heating to explosive, plasma-forming reactions. Contained are four works concerning laser-energy coupling: laser (i) heating and (ii) melting monitored using a mirage effect technique, (iii) the mechanical stress-power generated during high-powered laser ablation, and (iv) plasma-shielding. First, a photothermal deflection (PTD) technique is presented for monitoring heat transfer during modulated laser heating of opaque solids that have not undergone phase-change. Of main interest is the physical significance of the shape, magnitude, and phase for the temporal profile of the deflection signal. Considered are the effects that thermophysical properties, boundary conditions, and geometry of the target and optical probe-beam have on the deflection response. PTD is shown to monitor spatial and temporal changes in heat flux leaving the surface due to changes in laser energy coupling. The PTD technique is then extended to detect phase-change at the surface of a solid target. Experimental data shows the onset of melt for indium and tin targets. The conditions for which melt can be detected by PTD is analyzed in terms of geometry, incident power and pulse length, and thermophysical properties of the target and surroundings. Next, monitoring high-powered laser ablation of materials with stress-power is introduced. The motivation for considering stress-power is given, followed by a theoretical discussion of stress-power and how it is determined experimentally. Experiments are presented for the ablation of aluminum targets as a function of energy and intensity. The stress-power response is analyzed for its physical significance. Lastly, the influence of plasma-shielding during high-powered pulsed laser-material interactions is considered. Crater size, emission, and stress-power are measured to determine the role that the gas medium and laser pulse length have on plasma shielding

Resonantly diode-pumped continuous-wave and Q-switched Er:YAG laser at 1645 nm.

Science.gov (United States)

Chang, N W H; Simakov, N; Hosken, D J; Munch, J; Ottaway, D J; Veitch, P J

2010-06-21

We describe an efficient Er:YAG laser that is resonantly pumped using continuous-wave (CW) laser diodes at 1470 nm. For CW lasing, it emits 6.1 W at 1645 nm with a slope efficiency of 36%, the highest efficiency reported for an Er:YAG laser that is pumped in this manner. In Q-switched operation, the laser produces diffraction-limited pulses with an average power of 2.5 W at 2 kHz PRF. To our knowledge this is the first Q-switched Er:YAG laser resonantly pumped by CW laser diodes.

Resonance-enhanced laser-induced plasma spectroscopy: ambient gas effects

International Nuclear Information System (INIS)

Lui, S.L.; Cheung, N.H.

2003-01-01

When performing laser-induced plasma spectroscopy for elemental analysis, the sensitivity could be significantly enhanced if the plume was resonantly rekindled by a dye laser pulse. The extent of the enhancement was found to depend on the ambient gas. Air, nitrogen, helium, argon and xenon at pressures ranging from vacuum to 1 bar were investigated. In vacuum, the analyte signal was boosted because of reduced cooling, but it soon decayed as the plume freely expanded. By choosing the right ambient gas at the right pressure, the expanding plume could be confined as well as thermally insulated to maximize the analyte signal. For instance, an ambient of 13 mbar xenon yielded a signal-to-noise ratio of 110. That ratio was 53 when the pellet was ablated in air, and decreased further to 5 if the dye laser was tuned off resonance

IV-VI mid-IR tunable lasers and detectors with external resonant cavities

Science.gov (United States)

Zogg, H.; Rahim, M.; Khiar, A.; Fill, M.; Felder, F.; Quack, N.; Blunier, S.; Dual, J.

2009-08-01

Wavelength tunable emitters and detectors in the mid-IR wavelength region allow applications including thermal imaging and spectroscopy. Such devices may be realized using a resonant cavity. By mechanically changing the cavity length with MEMS mirror techniques, the wavelengths may be tuned over a considerable range. Vertical external cavity surface emitting lasers (VECSEL) may be applied for gas spectroscopy. Resonant cavity enhanced detectors (RCED) are sensitive at the cavity resonance only. They may be applied for low resolution spectroscopy, and, when arrays of such detectors are realized, as multicolor IR-FPA or IR-AFPA (IR-adaptive focal plane arrays). We review mid-infrared RCEDs and VECSELs using narrow gap IV-VI (lead chalcogenide) materials like PbTe and PbSe as the active medium. IV-VIs are fault tolerant and allow easy wavelength tuning. The VECSELs operate up to above room temperature and emit in the 4 - 5 μm range with a PbSe active layer. RCEDs with PbTe absorbing layers above 200 K operating temperature have higher sensitivities than the theoretical limit for a similar broad-band detector coupled with a passive tunable band-filter.

Multistage Coupling of Laser-Wakefield Accelerators with Curved Plasma Channels

Science.gov (United States)

Luo, J.; Chen, M.; Wu, W. Y.; Weng, S. M.; Sheng, Z. M.; Schroeder, C. B.; Jaroszynski, D. A.; Esarey, E.; Leemans, W. P.; Mori, W. B.; Zhang, J.

2018-04-01

Multistage coupling of laser-wakefield accelerators is essential to overcome laser energy depletion for high-energy applications such as TeV-level electron-positron colliders. Current staging schemes feed subsequent laser pulses into stages using plasma mirrors while controlling electron beam focusing with plasma lenses. Here a more compact and efficient scheme is proposed to realize the simultaneous coupling of the electron beam and the laser pulse into a second stage. A partly curved channel, integrating a straight acceleration stage with a curved transition segment, is used to guide a fresh laser pulse into a subsequent straight channel, while the electrons continue straight. This scheme benefits from a shorter coupling distance and continuous guiding of the electrons in plasma while suppressing transverse beam dispersion. Particle-in-cell simulations demonstrate that the electron beam from a previous stage can be efficiently injected into a subsequent stage for further acceleration while maintaining high capture efficiency, stability, and beam quality.

Resonance ionization mass spectrometry using tunable diode lasers

International Nuclear Information System (INIS)

Shaw, R.W.; Young, J.P.; Smith, D.H.

1990-01-01

Tunable semiconductor diode lasers will find many important applications in atomic spectroscopy. They exhibit the desirable attributes of lasers: narrow bandwidth, tunability, and spatial coherence. At the same time, they possess few of the disadvantages of other tunable lasers. They require no alignment, are simple to operate, and are inexpensive. Practical laser spectroscopic instruments can be envisioned. The authors have applied diode lasers to resonance ionization mass spectrometry (RIMS) of some of the lanthanide elements. Sub-Doppler resolution spectra have been recorded and have been used for atomic hyperfine structure analysis. Isotopically-selective ionization has been accomplished, even in cases where photons from a broadband dye laser are part of the overall ionization process and where the isotopic spectral shift is very small. A convenient RIMS instrument for isotope ratio measurements that employs only diode lasers, along with electric field ionization, should be possible

Conversion between EIT and Fano spectra in a microring-Bragg grating coupled-resonator system

Science.gov (United States)

Zhang, Zecen; Ng, Geok Ing; Hu, Ting; Qiu, Haodong; Guo, Xin; Wang, Wanjun; Rouifed, Mohamed Saïd; Liu, Chongyang; Wang, Hong

2017-08-01

A conversion between the electromagnetically induced transparency (EIT) transmission and Fano transmission is theoretically and experimentally demonstrated in an all-pass microring-Bragg grating (APMR-BG) coupled-resonator system. In this work, the coupling between the two resonators (the microring resonator and the Fabry-Perot resonator formed by two Bragg gratings) gives rise to the EIT and Fano transmissions. The resonant status strongly depends on the round-trip attenuation of the microring and the coupling strength. By tuning the coupling strength, the EIT and Fano transmissions can be controlled and converted. The device performance has been theoretically calculated and analyzed with a specially developed numerical model based on the transfer matrix method. The APMR-BG coupled-resonator systems with different gap widths were designed, fabricated, and characterized on a silicon-on-insulator (SOI) platform. The conversion of resonance was experimentally observed and verified. In addition, this on-chip system has the advantage of a small footprint, and the fabrication process is compatible with the planar waveguide fabrication process.

Spatiotemporal multiple coherence resonances and calcium waves in a coupled hepatocyte system

International Nuclear Information System (INIS)

Bao-Hua, Wang; Qi-Shao, Lu; Shu-Juan, Lü; Xiu-Feng, Lang

2009-01-01

Spatiotemporal multiple coherence resonances for calcium activities induced by weak Gaussian white noise in coupled hepatocytes are studied. It is shown that bi-resonances in hepatocytes are induced by the interplay and competition between noise and coupling of cells, in other words, the cell in network can be excited either by noise or by its neighbour via gap junction which can transfer calcium ions between cells. Furthermore, the intercellular annular calcium waves induced by noise are observed, in which the wave length decreases with noise intensity augmenting but increases monotonically with coupling strength increasing. And for a fixed noise level, there is an optimal coupling strength that makes the coherence resonance reach maximum. (general)

The role of ultrasound and magnetic resonance imaging in the evaluation of the forearm interosseous membrane. A review

International Nuclear Information System (INIS)

Rodriguez-Martin, Juan; Pretell-Mazzini, Juan

2011-01-01

The interosseous membrane of the forearm is an important structure to consider in cases of elbow and forearm trauma; it can be injured after elbow or forearm fractures, leading to longitudinal forearm instability. Diagnosis of interosseous membrane injuries is challenging, and failure in diagnosis may result in poor clinical outcomes and complications. Magnetic resonance imaging and ultrasound have shown to be valuable methods for the evaluation of this important structure. Both techniques have advantages and limitations, and its use should be adapted to each specific clinical scenario. This article presents an up-to-date literature review regarding the use of ultrasound and magnetic resonance imaging in the forearm interosseous membrane evaluation. (orig.)

The role of ultrasound and magnetic resonance imaging in the evaluation of the forearm interosseous membrane. A review

Energy Technology Data Exchange (ETDEWEB)

Rodriguez-Martin, Juan [Infanta Leonor University Hospital, Trauma and Orthopaedics, Shoulder and Elbow Unit, Madrid (Spain); Pretell-Mazzini, Juan [The Children' s Hospital of Philadelphia, Pediatric Orthopaedic Fellow, Division of Orthopaedic Surgery, Philadelphia, PA (United States)

2011-12-15

The interosseous membrane of the forearm is an important structure to consider in cases of elbow and forearm trauma; it can be injured after elbow or forearm fractures, leading to longitudinal forearm instability. Diagnosis of interosseous membrane injuries is challenging, and failure in diagnosis may result in poor clinical outcomes and complications. Magnetic resonance imaging and ultrasound have shown to be valuable methods for the evaluation of this important structure. Both techniques have advantages and limitations, and its use should be adapted to each specific clinical scenario. This article presents an up-to-date literature review regarding the use of ultrasound and magnetic resonance imaging in the forearm interosseous membrane evaluation. (orig.)

High resolution ultrasound and photoacoustic imaging of single cells

Directory of Open Access Journals (Sweden)

Eric M. Strohm

2016-03-01

Full Text Available High resolution ultrasound and photoacoustic images of stained neutrophils, lymphocytes and monocytes from a blood smear were acquired using a combined acoustic/photoacoustic microscope. Photoacoustic images were created using a pulsed 532 nm laser that was coupled to a single mode fiber to produce output wavelengths from 532 nm to 620 nm via stimulated Raman scattering. The excitation wavelength was selected using optical filters and focused onto the sample using a 20× objective. A 1000 MHz transducer was co-aligned with the laser spot and used for ultrasound and photoacoustic images, enabling micrometer resolution with both modalities. The different cell types could be easily identified due to variations in contrast within the acoustic and photoacoustic images. This technique provides a new way of probing leukocyte structure with potential applications towards detecting cellular abnormalities and diseased cells at the single cell level.

b-dipole transitions in trans-HOCO observed by far infrared laser magnetic resonance

International Nuclear Information System (INIS)

Sears, T.J.; Radford, H.E.; Moore, M.A.

1993-01-01

Far infrared laser magnetic resonance spectroscopy is used to measure components of 12 rotational transitions in the ground state of the HOCO radical. The transitions are all b-dipole in character in contrast to the a-dipole rotational spectrum previously reported [Radford, Wei, and Sears, J. Chem. Phys. 97, 3989 (1992)]. The new data determine the A rotational constant to high precision and allow the determination of several centrifugal distortion constants for the first time. The hyperfine coupling in the radical leads to observable splittings in several of the observed transitions and these are used to estimate two of the four expected nonzero hyperfine parameters in the radical

Laser impulse coupling at 130 fs

International Nuclear Information System (INIS)

Phipps, C.; Luke, J.; Funk, D.; Moore, D.; Glownia, J.; Lippert, T.

2006-01-01

We measured the momentum coupling coefficient C m and laser-generated ion drift velocity and temperature in the femtosecond (fs) region, over a laser intensity range from ablation threshold to about one hundred times threshold. Targets were several pure metals and three organic compounds. The organic compounds were exothermic polymers specifically developed for the micro-laser plasma thruster, and two of these used 'tuned absorbers' rather than carbon particles for laser absorption. The metals ranged from Li to W in atomic weight. We measured time of flight (TOF) profiles for ions. Specific impulse reached record values for this type of measurement and ablation efficiency was near 100%. These measurements extend the laser pulsewidth three orders of magnitude downward in pulsewidth relative to previous reports. Over this range, we found C m to be essentially constant. Ion velocity ranged from 60 to 180 km/s

Dynamics of multi-frequency oscillator ensembles with resonant coupling

International Nuclear Information System (INIS)

Lueck, S.; Pikovsky, A.

2011-01-01

We study dynamics of populations of resonantly coupled oscillators having different frequencies. Starting from the coupled van der Pol equations we derive the Kuramoto-type phase model for the situation, where the natural frequencies of two interacting subpopulations are in relation 2:1. Depending on the parameter of coupling, ensembles can demonstrate fully synchronous clusters, partial synchrony (only one subpopulation synchronizes), or asynchrony in both subpopulations. Theoretical description of the dynamics based on the Watanabe-Strogatz approach is developed. -- Highlights: → Kuramoto model is generalized on the case of resonantly interacting oscillators having frequency ratio 2:1. → Regimes of full and partial synchrony, as well as non-synchronous ones are reported. → Analytical description is developed on the basis of the Watanabe-Strogatz approach.

Dynamics of multi-frequency oscillator ensembles with resonant coupling

Energy Technology Data Exchange (ETDEWEB)

Lueck, S. [Department of Physics and Astronomy, Potsdam University, Karl-Liebknecht-Str. 24-25, 14476 Potsdam (Germany); Pikovsky, A., E-mail: pikovsky@stat.physik.uni-potsdam.de [Department of Physics and Astronomy, Potsdam University, Karl-Liebknecht-Str. 24-25, 14476 Potsdam (Germany)

2011-07-11

We study dynamics of populations of resonantly coupled oscillators having different frequencies. Starting from the coupled van der Pol equations we derive the Kuramoto-type phase model for the situation, where the natural frequencies of two interacting subpopulations are in relation 2:1. Depending on the parameter of coupling, ensembles can demonstrate fully synchronous clusters, partial synchrony (only one subpopulation synchronizes), or asynchrony in both subpopulations. Theoretical description of the dynamics based on the Watanabe-Strogatz approach is developed. -- Highlights: → Kuramoto model is generalized on the case of resonantly interacting oscillators having frequency ratio 2:1. → Regimes of full and partial synchrony, as well as non-synchronous ones are reported. → Analytical description is developed on the basis of the Watanabe-Strogatz approach.

Jones matrix formulation of a Porro prism laser resonator with waveplates: theoretical and experimental analysis

Science.gov (United States)

Agrawal, L.; Bhardwaj, A.; Pal, S.; Kumar, A.

2007-11-01

This article presents the results of a detailed theoretical and experimental analysis carried out on a folded Z-shaped polarization coupled, electro-optically Q-switched laser resonator with Porro prisms and waveplates. The advantages of adding waveplates in a Porro prism resonator have been explored for creating high loss condition prior to Q-switching and obtaining variable reflectivity with fixed orientation of Porro prism. Generalized expressions have been derived in terms of azimuth angles and phase shifts introduced by the polarizing elements. These expressions corroborate with known reported results under appropriate substitutions. A specific case of a crossed Porro prism diode-pumped Nd:YAG laser has been theoretically and experimentally investigated. In the feedback arm, a 0.57λ waveplate oriented at 135° completely compensates the phase shift of a fused silica Porro prism and provides better tolerances than a BK-7 prism/0.60λ waveplate combination to stop prelasing. The fused silica prism/0.57λ combination with waveplate at 112° acts like a 100% mirror and was utilized for optimization of free running performance. The effective reflectivity was determined for various orientations of the quarter waveplate in the gain arm to numerically estimate the Q-switched laser pulse parameters through rate equation analysis. Experimental results match well with the theoretical analysis.

Lasing by driven atoms-cavity system in collective strong coupling regime.

Science.gov (United States)

Sawant, Rahul; Rangwala, S A

2017-09-12

The interaction of laser cooled atoms with resonant light is determined by the natural linewidth of the excited state. An optical cavity is another optically resonant system where the loss from the cavity determines the resonant optical response of the system. The near resonant combination of an optical Fabry-Pérot cavity with laser cooled and trapped atoms couples two distinct optical resonators via light and has great potential for precision measurements and the creation of versatile quantum optics systems. Here we show how driven magneto-optically trapped atoms in collective strong coupling regime with the cavity leads to lasing at a frequency red detuned from the atomic transition. Lasing is demonstrated experimentally by the observation of a lasing threshold accompanied by polarization and spatial mode purity, and line-narrowing in the outcoupled light. Spontaneous emission into the cavity mode by the driven atoms stimulates lasing action, which is capable of operating as a continuous wave laser in steady state, without a seed laser. The system is modeled theoretically, and qualitative agreement with experimentally observed lasing is seen. Our result opens up a range of new measurement possibilities with this system.

Coupled superconducting resonant cavities for a heavy ion linac

Energy Technology Data Exchange (ETDEWEB)

Shepard, K W [Argonne National Lab., IL (United States); Roy, A [Nuclear Science Center, New Delhi (India)

1992-11-01

A design for a superconducting niobium slow-wave accelerating structure has been explored that may have performance and cost advantages over existing technology. The option considered is an array of pairs of quarter-wave coaxial-line resonant cavities, the two elements of each pair strongly coupled through a short superconducting transmission line. In the linac formed by such an array, each paired structure is independently phased. A disadvantage of two-gap slow wave structures is that each cavity is relatively short, so that a large number of independently-phased elements is required for a linac. Increasing the number of drift tubes per cavity reduces the number of independently-phased elements but at the cost of reducing the range of useful velocity acceptance for each element. Coupling two cavities splits the accelerating rf eigenmode into two resonant modes each of which covers a portion of the full velocity acceptance range of the original, single cavity mode. Using both of these resonant modes makes feasible the use of coupled cavity pairs for a linac with little loss in velocity acceptance. (Author) 2 figs., 8 refs.

Coupled superconducting resonant cavities for a heavy ion linac

International Nuclear Information System (INIS)

Shepard, K.W.; Roy, A.

1992-01-01

A design for a superconducting niobium slow-wave accelerating structure has been explored that may have performance and cost advantages over existing technology. The option considered is an array of pairs of quarter-wave coaxial-line resonant cavities, the two elements of each pair strongly coupled through a short superconducting transmission line. In the linac formed by such an array, each paired structure is independently phased. A disadvantage of two-gap slow wave structures is that each cavity is relatively short, so that a large number of independently-phased elements is required for a linac. Increasing the number of drift tubes per cavity reduces the number of independently-phased elements but at the cost of reducing the range of useful velocity acceptance for each element. Coupling two cavities splits the accelerating rf eigenmode into two resonant modes each of which covers a portion of the full velocity acceptance range of the original, single cavity mode. Using both of these resonant modes makes feasible the use of coupled cavity pairs for a linac with little loss in velocity acceptance. (Author) 2 figs., 8 refs

Vanishing chiral couplings in the large-NC resonance theory

International Nuclear Information System (INIS)

Portoles, Jorge; Rosell, Ignasi; Ruiz-Femenia, Pedro

2007-01-01

The construction of a resonance theory involving hadrons requires implementing the information from higher scales into the couplings of the effective Lagrangian. We consider the large-N C chiral resonance theory incorporating scalars and pseudoscalars, and we find that, by imposing LO short-distance constraints on form factors of QCD currents constructed within this theory, the chiral low-energy constants satisfy resonance saturation at NLO in the 1/N C expansion

Eddy-current effect on resonant magnetoelectric coupling in magnetostrictive-piezoelectric laminated composites

Science.gov (United States)

Liu, Guoxi; Zhang, Chunli; Chen, Weiqiu; Dong, Shuxiang

2013-07-01

An analytical model of resonant magnetoelectric (ME) coupling in magnetostrictive (MS)-piezoelectric (PE) laminated composites in consideration of eddy-current effect in MS layer using equivalent circuit method is presented. Numerical calculations show that: (1) the eddy-current has a strong effect on ME coupling in MS-PE laminated composites at resonant frequency; and (2) the resonant ME coupling is then significantly dependent on the sizes of ME laminated composites, which were neglected in most previous theoretical analyses. The achieved results provide a theoretical guidance for the practice engineering design, manufacture, and application of ME laminated composites and devices.

Switchable coupling for superconducting qubits using double resonance in the presence of crosstalk

International Nuclear Information System (INIS)

Ashhab, S.; Nori, Franco

2007-01-01

Several methods have been proposed recently to achieve switchable coupling between superconducting qubits. We discuss some of the main considerations regarding the feasibility of implementing one of those proposals: The double-resonance method. We analyze mainly issues related to the achievable effective coupling strength and the effects of crosstalk on this coupling mechanism. We also find a crosstalk-assisted coupling channel that can be an attractive alternative when implementing the double-resonance coupling proposal

Realizing a Circuit Analog of an Optomechanical System with Longitudinally Coupled Superconducting Resonators

OpenAIRE

Eichler, C.; Petta, J. R.

2017-01-01

We realize a superconducting circuit analog of the generic cavity-optomechanical Hamiltonian by longitudinally coupling two superconducting resonators, which are an order of magnitude different in frequency. We achieve longitudinal coupling by embedding a superconducting quantum interference device (SQUID) into a high frequency resonator, making its resonance frequency depend on the zero point current fluctuations of a nearby low frequency LC-resonator. By employing sideband drive fields we e...

Coupled-resonator-induced plasmonic bandgaps.

Science.gov (United States)

Wang, Yujia; Sun, Chengwei; Gong, Qihuang; Chen, Jianjun

2017-10-15

By drawing an analogy with the conventional photonic crystals, the plasmonic bandgaps have mainly employed the periodic metallic structures, named as plasmonic crystals. However, the sizes of the plasmonic crystals are much larger than the wavelengths, and the large sizes considerably decrease the density of the photonic integration circuits. Here, based on the coupled-resonator effect, the plasmonic bandgaps are experimentally realized in the subwavelength waveguide-resonator structure, which considerably decreases the structure size to subwavelength scales. An analytic model and the phase analysis are established to explain this phenomenon. Both the experiment and simulation show that the plasmonic bandgap structure has large fabrication tolerances (>20%). Instead of the periodic metallic structures in the bulky plasmonic crystals, the utilization of the subwavelength plasmonic waveguide-resonator structure not only significantly shrinks the bandgap structure to be about λ 2 /13, but also expands the physics of the plasmonic bandgaps. The subwavelength dimension, together with the waveguide configuration and robust realization, makes the bandgap structure easy to be highly integrated on chips.

Characterization of complementary electric field coupled resonant surfaces

Science.gov (United States)

Hand, Thomas H.; Gollub, Jonah; Sajuyigbe, Soji; Smith, David R.; Cummer, Steven A.

2008-11-01

We present angle-resolved free-space transmission and reflection measurements of a surface composed of complementary electric inductive-capacitive (CELC) resonators. By measuring the reflection and transmission coefficients of a CELC surface with different polarizations and particle orientations, we show that the CELC only responds to in-plane magnetic fields. This confirms the Babinet particle duality between the CELC and its complement, the electric field coupled LC resonator. Characterization of the CELC structure serves to expand the current library of resonant elements metamaterial designers can draw upon to make unique materials and surfaces.

High-brightness fiber-coupled pump laser development

Science.gov (United States)

Price, Kirk; Karlsen, Scott; Leisher, Paul; Martinsen, Robert

2010-02-01

We report on the continued development of high brightness laser diode modules at nLIGHT Photonics. These modules, based on nLIGHT's PearlTM product platform, demonstrate excellence in output power, brightness, wavelength stabilization, and long wavelength performance. This system, based on 14 single emitters, is designed to couple diode laser light into a 105 μm fiber at an excitation NA of under 0.14. We demonstrate over 100W of optical power at 9xx nm with a diode brightness exceeding 20 MW/cm2-str with an operating efficiency of approximately 50%. Additional results show over 70W of optical coupled at 8xx nm. Record brilliance at wavelengths 14xx nm and longer will also be demonstrated, with over 15 W of optical power with a beam quality of 7.5 mm-mrad. These results of high brightness, high efficiency, and wavelength stabilization demonstrate the pump technology required for next generation solid state and fiber lasers.

Optical detection of ultrasound using an apertureless near-field scanning optical microscopy system

Science.gov (United States)

Ahn, Phillip; Zhang, Zhen; Sun, Cheng; Balogun, Oluwaseyi

2013-01-01

Laser ultrasonics techniques are power approaches for non-contact generation and detection of high frequency ultrasound on a local scale. In these techniques, optical diffraction limits the spatial information that can be accessed from a measurement. In order to improve the lateral spatial resolution, we incorporate an apertureless near-field scanning optical microscope (aNSOM) into laser ultrasonics setup for local detection of laser generated ultrasound. The aNSOM technique relies on the measurement of a weak backscattered near-field light intensity resulting from the oblique illumination of a nanoscale probe-tip positioned close to a sample surface. We enhance the optical near-field intensity by coupling light to surface plasmon polaritons (SPPs) on the shaft of an atomic force microscopy (AFM) cantilever. The SPPs propagate down the AFM shaft, localize at the tip apex, and are backscattered to the far-field when the separation distance between the probe tip and the sample surface is comparable to the probe-tip radius. The backscattered near-field intensity is dynamically modulated when an ultrasonic wave arrives at the sample surface leading to a transient change in the tip-sample separation distance. We present experimental results detailing measurement of broadband and narrowband laser generated ultrasound in solids with frequencies reaching up to 180 MHz range.

Self-resonant wakefield excitation by intense laser pulse in plasmas

International Nuclear Information System (INIS)

Andreev, N.E.; Pogosova, A.A.; Gorbunov, L.M.; Ramazashvili, R.R.; Kirsanov, V.I.

1993-01-01

It is demonstrated by theoretical analysis and numerical calculations that in an underdense plasma the process of three-dimensional evolution of the short and strong laser pulse (with duration equal to several plasma periods) leads to compression and self-modulation of the pulse, so that during a fairly long period of time beats of pulse amplitude generates resonantly a strong and stable plasma wakefield. The intensity of the wake-field is so high that it can provide a new promising outlook for the plasma based accelerator concept. Linear analysis of dispersion relation predicts that taking into account transverse component of wavenumber considerably increases the growth rate of resonance instability of the pulse. The numerical simulations demonstrate that considered self-focusing and resonant-modulation instability are essentially three dimensional processes. Laser field evolution in each transverse cross section of the pulse is synchronized by the regular structure of plasma wave that is excited by the pulse. The considered effect of resonant modulation has a threshold. For the pulses with the intensity below the threshold the refraction dominates and no modulation appears. The studied phenomenon can be referred to as the Self-Resonant Wakefield (SRWF) excitation that is driven by self-focusing and self-modulation of laser pulse with quite a moderate initial duration. In fact, this method of excitation differs from both suggested in Ref.1 (PBWA) and in Refs.2,3 (LWFA), being even more than the combination of these concepts. Unlike the first scheme it does not require initially the two-frequency laser pulse, since the modulation here appears in the most natural way due to evolution of the pulse. In contrast with the LWFA, the considered SRWF generation scheme gives the possibility to raise the intensity of wake-excitation due to pulse self-focusing ( initial stage) and self modulation (second stage)

Near resonant absorption by atoms in intense fluctuating laser fields

International Nuclear Information System (INIS)

Smith, S.J.

1994-01-01

The objective of this program was to make quantitative measurements of the effects of higher-order phase/frequency correlations in a laser beam on nonlinear optical absorption processes in atoms. The success of this program was due in large part to a unique experimental capability for modulating the extracavity beam of a stabilized (approx-lt 200 kHz) continuous-wave laser with statistically-well-characterized stochastic phase (or frequency) fluctuations, in order to synthesize laser bandwidths to ∼20 MHz (depending on noise amplitude), with profiles variable between Gaussian and Lorentzian (depending on noise bandwidth). Laser driven processes investigated included the following: (1) the optical Autler-Towns effect in the 3S 1/2 (F = 2, M F = 2) → 3P 3/2 (F = 3, M F = 3) two- level Na resonance, using a weak probe to the 4D 5/2 level; (2) the variance and spectra of fluorescence intensity fluctuations in the two-level Na resonance; (3) the Hanle effect in the 1 S 0 - 3 P 1 , transition at λ = 555.6 nm in 174 Yb; (4) absorption (and gain) of a weak probe, when the probe is a time-delayed replica of the resonant (with the two-level Na transition) pump laser; and (5) four-wave-mixing in a phase-conjugate geometry, in a sodium cell, and, finally, in a diffuse atomic sodium beam. The experimental results from these several studies have provided important confirmation of advanced theoretical methods

Formation and coupling of band gaps in a locally resonant elastic system comprising a string with attached resonators

International Nuclear Information System (INIS)

Xiao Yong; Mace, Brian R.; Wen Jihong; Wen Xisen

2011-01-01

A uniform string with periodically attached spring-mass resonators represents a simple locally resonant continuous elastic system whose band gap mechanisms are basic to more general and complicated problems. In this Letter, analytical models with explicit formulations are provided to understand the band gap mechanisms of such a system. Some interesting phenomena are demonstrated and discussed, such as asymmetric/symmetric attenuation behavior within a resonance gap, and the realization of a super-wide gap due to exact coupling between Bragg and resonance gaps. In addition, some approximate formulas for the evaluation of low frequency resonance gaps are derived using an approach different from existing investigations. - Research highlights: → We examine band gaps in a special one-dimensional locally resonant system. → Bragg and resonance gaps co-exist. → Explicit formulas for locating band edges are derived. → Exact physical models are used to clarify the band gap formation mechanisms. → Coupling between Bragg and resonance gaps leads to a super-wide gap.

Quantum heat engine with coupled superconducting resonators

DEFF Research Database (Denmark)

Hardal, Ali Ümit Cemal; Aslan, Nur; Wilson, C. M.

2017-01-01

the differences between the quantum and classical descriptions of our system by solving the quantum master equation and classical Langevin equations. Specifically, we calculate the mean number of excitations, second-order coherence, as well as the entropy, temperature, power, and mean energy to reveal......We propose a quantum heat engine composed of two superconducting transmission line resonators interacting with each other via an optomechanical-like coupling. One resonator is periodically excited by a thermal pump. The incoherently driven resonator induces coherent oscillations in the other one...... the signatures of quantum behavior in the statistical and thermodynamic properties of the system. We find evidence of a quantum enhancement in the power output of the engine at low temperatures....

Polarization control of intermediate state absorption in resonance-mediated multi-photon absorption process

International Nuclear Information System (INIS)

Xu, Shuwu; Yao, Yunhua; Jia, Tianqing; Ding, Jingxin; Zhang, Shian; Sun, Zhenrong; Huang, Yunxia

2015-01-01

We theoretically and experimentally demonstrate the control of the intermediate state absorption in an (n + m) resonance-mediated multi-photon absorption process by the polarization-modulated femtosecond laser pulse. An analytical solution of the intermediate state absorption in a resonance-mediated multi-photon absorption process is obtained based on the time-dependent perturbation theory. Our theoretical results show that the control efficiency of the intermediate state absorption by the polarization modulation is independent of the laser intensity when the transition from the intermediate state to the final state is coupled by the single-photon absorption, but will be affected by the laser intensity when this transition is coupled by the non-resonant multi-photon absorption. These theoretical results are experimentally confirmed via a two-photon fluorescence control in (2 + 1) resonance-mediated three-photon absorption of Coumarin 480 dye and a single-photon fluorescence control in (1 + 2) resonance-mediated three-photon absorption of IR 125 dye. (paper)

Resonance-enhanced optical forces between coupled photonic crystal slabs.

Science.gov (United States)

Liu, Victor; Povinelli, Michelle; Fan, Shanhui

2009-11-23

The behaviors of lateral and normal optical forces between coupled photonic crystal slabs are analyzed. We show that the optical force is periodic with displacement, resulting in stable and unstable equilibrium positions. Moreover, the forces are strongly enhanced by guided resonances of the coupled slabs. Such enhancement is particularly prominent near dark states of the system, and the enhancement effect is strongly dependent on the types of guided resonances involved. These structures lead to enhancement of light-induced pressure over larger areas, in a configuration that is directly accessible to externally incident, free-space optical beams.

Excitation of resonances of microspheres on an optical fiber

Science.gov (United States)

Serpengüzel, A.; Arnold, S.; Griffel, G.

1995-04-01

Morphology-dependent resonances (MDR's) of solid microspheres are excited by using an optical fiber coupler. The narrowest measured MDR linewidths are limited by the excitation laser linewidth ( < 0.025 nm). Only MDR's, with an on-resonance to off-resonance intensity ratio of 104, contribute to scattering. The intensity of various resonance orders is understood by the localization principle and the recently developed generalized Lorentz-Mie theory. The microsphere fiber system has potential for becoming a building block in dispersive microphotonics. The basic physics underlying our approach may be considered a harbinger for the coupling of active photonic microstructures such as microdisk lasers.

Isotopically selective RIMS of rare radionuclides by double-resonance excitation with cw lasers

International Nuclear Information System (INIS)

Bushaw, B.A.; Munley, J.T.

1990-09-01

Double-resonance, Resonance Ionization Mass Spectroscopy (RIMS) using two single-frequency dye lasers and a CO 2 laser for photoionization has been shown to be both extremely sensitive and highly selective. Measurements on the radioisotope 210 Pb have demonstrated optical selectivity in excess of 10 9 and detection limits of less than 1 femtogram

Study of gain-coupled distributed feedback laser based on high order surface gain-coupled gratings

Science.gov (United States)

Gao, Feng; Qin, Li; Chen, Yongyi; Jia, Peng; Chen, Chao; Cheng, LiWen; Chen, Hong; Liang, Lei; Zeng, Yugang; Zhang, Xing; Wu, Hao; Ning, Yongqiang; Wang, Lijun

2018-03-01

Single-longitudinal-mode, gain-coupled distributed feedback (DFB) lasers based on high order surface gain-coupled gratings are achieved. Periodic surface metal p-contacts with insulated grooves realize gain-coupled mechanism. To enhance gain contrast in the quantum wells without the introduction of effective index-coupled effect, groove length and depth were well designed. Our devices provided a single longitudinal mode with the maximum CW output power up to 48.8 mW/facet at 971.31 nm at 250 mA without facet coating, 3dB linewidth (39 dB). Optical bistable characteristic was observed with a threshold current difference. Experimentally, devices with different cavity lengths were contrasted on power-current and spectrum characteristics. Due to easy fabrication technique and stable performance, it provides a method of fabricating practical gain-coupled distributed feedback lasers for commercial applications.

Magnetic resonance guided focalized ultrasound thermo-ablation: A promising oncologic local therapy

International Nuclear Information System (INIS)

Iannessi, A.; Doyen, J.; Leysalle, A.; Thyss, A.

2014-01-01

Pain management of bone metastases is usually made using systemic and local therapy. Even though radiations are nowadays the gold standard for painful metastases, innovations regarding minimally invasive treatment approaches have been developed because of the existing non-responder patients [1]. Indeed, cementoplasty and thermo-ablations like radiofrequency or cryotherapy have shown to be efficient on pain [2-4]. Among thermo-therapy, magnetic resonance guided focalized ultrasound is now a new non-invasive weapon for bone pain palliation. (authors)

DIFFRACTION SYNCHRONIZATION OF LASERS,

Science.gov (United States)

semiconductor lasers while suppressing parasitic generation in the plane of the mirror. The diffraction coupling coefficient of open resonators is calculated, and the stability conditions of the synchronized system is determined.

Laser heating of large noble gas clusters: from the resonant to the relativistic interaction regimes

Energy Technology Data Exchange (ETDEWEB)

Gumbrell, E T; Moore, A S; Clark, E L; Garbett, W J; Comley, A J; Edwards, R D; Eagleton, R E [Plasma Physics Division, AWE Aldermaston, Reading RG7 4PR (United Kingdom); Lazarus, J A; Nilson, P M; Robinson, J S; Hohenberger, M; Symes, D R; Smith, R A [Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom); Clarke, R J [Rutherford Appleton Laboratory, Chilton OX11 0QX (United Kingdom)], E-mail: edward.gumbrell@awe.co.uk, E-mail: r.a.smith@imperial.ac.uk

2008-12-15

Wide-ranging measurements of sub-picosecond laser interactions with large noble gas cluster targets have been conducted in order to help clarify the nature and extent of the underlying laser-plasma heating. Within the sub-relativistic vacuum irradiance range of 10{sup 16}-10{sup 17} W cm{sup -2}, we find that electron temperatures measured with continuum x-ray spectroscopy exhibit a pronounced multi-keV enhancement. Analysis indicates this behaviour to be consistent with collisional or collisionless resonant heating mechanisms. We also present the first measurements of laser-to-cluster energy deposition at relativistic vacuum irradiances, our data demonstrating absorption fractions of 90% or more. Optical probing was used to resolve the onset of a supersonic ionization front resulting from this very high absorption, and shows that despite significant pre-focus heating, the greatest plasma energy densities can be generated about the vacuum focus position. Electron energy spectra measurements confirm that laser-plasma super-heating occurs, and together with ion data establish that relativistic laser-plasma coupling in atomic clusters can take place without significant MeV particle beam production. In conjunction with optical self-emission data, the optical probing also indicates laser pre-pulse effects at peak vacuum irradiance of 5 x 10{sup 19} W cm{sup -2}. Laser absorption, plasma heating and energy transport data are supported throughout with analytical and numerical modelling.

Multiple resonance compensation for betatron coupling and its equivalence with matrix method

CERN Document Server

De Ninno, G

1999-01-01

Analyses of betatron coupling can be broadly divided into two categories: the matrix approach that decouples the single-turn matrix to reveal the normal modes and the hamiltonian approach that evaluates the coupling in terms of the action of resonances in perturbation theory. The latter is often regarded as being less exact but good for physical insight. The common opinion is that the correction of the two closest sum and difference resonances to the working point is sufficient to reduce the off-axis terms in the 4X4 single-turn matrix, but this is only partially true. The reason for this is explained, and a method is developed that sums to infinity all coupling resonances and, in this way, obtains results equivalent to the matrix approach. The two approaches is discussed with reference to the dynamic aperture. Finally, the extension of the summation method to resonances of all orders is outlined and the relative importance of a single resonance compared to all resonances of a given order is analytically desc...

Qubit Coupled Mechanical Resonator in an Electromechanical System

Science.gov (United States)

Hao, Yu

This thesis describes the development of a hybrid quantum electromechanical system. In this system the mechanical resonator is capacitively coupled to a superconducting transmon which is embedded in a superconducting coplanar waveguide (CPW) cavity. The difficulty of achieving high quality of superconducting qubit in a high-quality voltage-biased cavity is overcome by integrating a superconducting reflective T-filter to the cavity. Further spectroscopic and pulsed measurements of the hybrid system demonstrate interactions between the ultra-high frequency mechanical resonator and transmon qubit. The noise of mechanical resonator close to ground state is measured by looking at the spectroscopy of the transmon. At last, fabrication and tests of membrane resonators are discussed.

Bicritical behaviors observed in coupled diode resonators

International Nuclear Information System (INIS)

Kim, Youngtae

2004-01-01

We have investigated bicritical behaviors of unidirectionally coupled diode resonators having a period doubling route to chaos. Depending on the dynamical states of the drive subsystem, the response subsystem showed a dynamical behavior other than that of the uncoupled system. The experimental results agreed well with the results obtained from the simulation of unidirectionally coupled logistic maps and oscillators. A new type of scaling behavior and a power spectrum of the hyperchaotic attractor appearing near a bicritical point were also observed.

Coupled modes, frequencies and fields of a dielectric resonator and a cavity using coupled mode theory

Science.gov (United States)

Elnaggar, Sameh Y.; Tervo, Richard; Mattar, Saba M.

2014-01-01

Probes consisting of a dielectric resonator (DR) inserted in a cavity are important integral components of electron paramagnetic resonance (EPR) spectrometers because of their high signal-to-noise ratio. This article studies the behavior of this system, based on the coupling between its dielectric and cavity modes. Coupled-mode theory (CMT) is used to determine the frequencies and electromagnetic fields of this coupled system. General expressions for the frequencies and field distributions are derived for both the resulting symmetric and anti-symmetric modes. These expressions are applicable to a wide range of frequencies (from MHz to THz). The coupling of cavities and DRs of various sizes and their resonant frequencies are studied in detail. Since the DR is situated within the cavity then the coupling between them is strong. In some cases the coupling coefficient, κ, is found to be as high as 0.4 even though the frequency difference between the uncoupled modes is large. This is directly attributed to the strong overlap between the fields of the uncoupled DR and cavity modes. In most cases, this improves the signal to noise ratio of the spectrometer. When the DR and the cavity have the same frequency, the coupled electromagnetic fields are found to contain equal contributions from the fields of the two uncoupled modes. This situation is ideal for the excitation of the probe through an iris on the cavity wall. To verify and validate the results, finite element simulations are carried out. This is achieved by simulating the coupling between a cylindrical cavity's TE011 and the dielectric insert's TE01δ modes. Coupling between the modes of higher order is also investigated and discussed. Based on CMT, closed form expressions for the fields of the coupled system are proposed. These expressions are crucial in the analysis of the probe's performance.

Magneto-laser-ultrasonic therapy. Particular methodic of different diseases treatment. Scientific materials used in practice. V.4(2)

International Nuclear Information System (INIS)

Samosyuk, I.Z.; Chukhraev, N.V.; Myasnikov, V.G.; Samosyuk, N.I.

2001-01-01

Contemporary data about the use of magnetotherapy, ultrasound and magnetolaser therapy in resonance energy ranges are presented in this book. Practical methodics of simultaneous and combined use of these physical factors in different branches of clinical medicine (neurology, cardiology, gastroenterology and others) are described. Modern principles of the sensitive zone choice, bases of biorhythmic and resonance phenomena are presented. Practical uses of them became more and more important in physiotherapy and acupuncture. Diseases of different organs are considered, and magnetic, laser and ultrasound mehtods of their treatment are discussed. Special attention is paid to the use of magneto-laser and low-frequency ultrasonic therapy methods for diabetus melitus and respiratory organ treatment. Diseases of urinary tract, of ischemia, insult, ophthalmological ones and series of surgery profile diseases are considered in connection with different modern treatment methods of them. Review of cardiovascular, skin, digestive system diseases, those of ophtalmology, stomatology, otolaryngology nervous-psychic violations is presented and optimum methods of their treatment are recommended. The most part of magneto-laser-ultrasound therapy uses refers to the new generation of series 'MIT' and 'MIT-11' apparata which combine all three treatment factors

Cyclotron resonant gas breakdown with a 1.22-nm 13CH3F laser

International Nuclear Information System (INIS)

Hacker, M.P.; Lax, B.; Metz, R.N.; Temkin, R.J.

1979-01-01

Cyclotron-resonant laser-induced gas breakdown has been studied for the first time in the transverse geometry, using 1.222-nm 13 CH 3 F laser radiation propagating perpendicular to the magnetic field axis. The line shape of absorbed laser radiation versus magnetic field near electron cyclotron resonance (87.75 kG) indicates a strong dependence of the line shape on the focused laser intensity. This dependence is not predicted by the standard equilibrium theory of high-frequency gas breakdown in a magnetic field. We have developed an analytic theory to explain the observed line shapes. The theory takes into account the laser propagation characteristics, in particular that there is nonuniform ionization due to strong resonant absorption of the laser radiation in a length comparable to or shorter than that of the laser focal volume. The transverse geometry simplifies the theoretical analysis because the observed line shapes are not significantly affected by Doppler broadening. Extensive data have been obtained on the fraction of laser pulse energy absorbed in the gas breakdown volume as a function of magnetic field, helium gas pressure, and incident laser pulse energy. Good quantitative agreement is obtained between the observed laser pulse absorption line shapes and the nonuniform ionization theory

Nonlinear resonant ultrasound spectroscopy (NRUS) applied to damage assessment in bone

Science.gov (United States)

Muller, Marie; Sutin, Alexander; Guyer, Robert; Talmant, Maryline; Laugier, Pascal; Johnson, Paul A.

2005-12-01

Nonlinear resonant ultrasound spectroscopy (NRUS) is a resonance-based technique exploiting the significant nonlinear behavior of damaged materials. In NRUS, the resonant frequency(ies) of an object is studied as a function of the excitation level. As the excitation level increases, the elastic nonlinearity is manifest by a shift in the resonance frequency. This study shows the feasibility of this technique for application to damage assessment in bone. Two samples of bovine cortical bone were subjected to progressive damage induced by application of mechanical cycling. Before cycling commenced, and at each step in the cycling process, NRUS was applied for damage assessment. For independent assessment of damage, high-energy x-ray computed tomography imaging was performed but was only useful in identifying the prominent cracks. As the integral quantity of damage increased, NRUS revealed a corresponding increase in the nonlinear response. The measured change in nonlinear response is much more sensitive than the change in linear modulus. The results suggest that NRUS could be a potential tool for micro-damage assessment in bone. Further work must be carried out for a better understanding of the physical nature of damaged bone and for the ultimate goal of the challenging in vivo implementation of the technique.

Coupling ultracold atoms to a superconducting coplanar waveguide resonator

OpenAIRE

Hattermann, H.; Bothner, D.; Ley, L. Y.; Ferdinand, B.; Wiedmaier, D.; Sárkány, L.; Kleiner, R.; Koelle, D.; Fortágh, J.

2017-01-01

We demonstrate coupling of magnetically trapped ultracold $^87$Rb ground state atoms to a coherently driven superconducting coplanar resonator on an integrated atom chip. We measure the microwave field strength in the cavity through observation of the AC shift of the hyperfine transition frequency when the cavity is driven off-resonance from the atomic transition. The measured shifts are used to reconstruct the field in the resonator, in close agreement with transmission measurements of the c...

Photonic Molecule Lasers Revisited

Science.gov (United States)

Gagnon, Denis; Dumont, Joey; Déziel, Jean-Luc; Dubé, Louis J.

2014-05-01

Photonic molecules (PMs) formed by coupling two or more optical resonators are ideal candidates for the fabrication of integrated microlasers, photonic molecule lasers. Whereas most calculations on PM lasers have been based on cold-cavity (passive) modes, i.e. quasi-bound states, a recently formulated steady-state ab initio laser theory (SALT) offers the possibility to take into account the spectral properties of the underlying gain transition, its position and linewidth, as well as incorporating an arbitrary pump profile. We will combine two theoretical approaches to characterize the lasing properties of PM lasers: for two-dimensional systems, the generalized Lorenz-Mie theory will obtain the resonant modes of the coupled molecules in an active medium described by SALT. Not only is then the theoretical description more complete, the use of an active medium provides additional parameters to control, engineer and harness the lasing properties of PM lasers for ultra-low threshold and directional single-mode emission. We will extend our recent study and present new results for a number of promising geometries. The authors acknowledge financial support from NSERC (Canada) and the CERC in Photonic Innovations of Y. Messaddeq.

Quantum transport in coupled resonators enclosed synthetic magnetic flux

International Nuclear Information System (INIS)

Jin, L.

2016-01-01

Quantum transport properties are instrumental to understanding quantum coherent transport processes. Potential applications of quantum transport are widespread, in areas ranging from quantum information science to quantum engineering, and not restricted to quantum state transfer, control and manipulation. Here, we study light transport in a ring array of coupled resonators enclosed synthetic magnetic flux. The ring configuration, with an arbitrary number of resonators embedded, forms a two-arm Aharonov–Bohm interferometer. The influence of magnetic flux on light transport is investigated. Tuning the magnetic flux can lead to resonant transmission, while half-integer magnetic flux quantum leads to completely destructive interference and transmission zeros in an interferometer with two equal arms. -- Highlights: •The light transport is investigated through ring array of coupled resonators enclosed synthetic magnetic field. •Aharonov–Bohm ring interferometer of arbitrary configuration is investigated. •The half-integer magnetic flux quantum leads to destructive interference and transmission zeros for two-arm at equal length. •Complete transmission is available via tuning synthetic magnetic flux.

Resonantly-pumped soft-x-ray lasers using ICF drivers

International Nuclear Information System (INIS)

Hagelstein, P.L.

1982-12-01

Some aspects of laser design relating to experiments planned for the NOVETTE laser system at Livermore in early 1983 are discussed. The experiments are aimed at testing several resonantly-pumped lasers with transition energies between 42.3 eV and 153 eV. These experiments follow several years of theoretical work, a set of flashlamp characterization experiments performed on the SHIVA laser system (LLNL) in December, 1981, and some high precision spectroscopic studies carried out at KMS during the summer of 1982. Some of the major physics design issues as the relate to the experiments, and some of the numerical simulations that have been carried out so far are reviewed

High-power fiber-coupled pump lasers for fiber lasers

Science.gov (United States)

Kasai, Yohei; Aizawa, Takuya; Tanaka, Daiichiro

2018-02-01

We present high-power fiber-coupled pump modules utilized effectively for ultra-high power single-mode (SM) fiber lasers. Maximum output power of 392 W was achieved at 23 A for 915 nm pump, and 394 W for 976 nm pump. Fiber core diameter is 118 μm and case temperature is 25deg. C. Polarization multiplexing technique was newly applied to our optical system. High-reliability of the laser diodes (LD) at high-power operation has been demonstrated by aging tests. Advanced package structure was developed that manages uncoupled light around input end of the fiber. 800 hours continuous drive with uncoupled light power of 100 W has been achieved.

XeCl excimer laser with new prism resonator configurations and its performance characteristics

Energy Technology Data Exchange (ETDEWEB)

Benerji, N. S., E-mail: nsb@rrcat.gov.in, E-mail: bsingh@rrcat.gov.in; Singh, A.; Varshnay, N.; Singh, Bijendra, E-mail: nsb@rrcat.gov.in, E-mail: bsingh@rrcat.gov.in [Excimer Laser Section, LMPD, Raja Ramanna Center for Advanced Technology, Indore 452013 (India)

2015-07-15

New resonator cavity configurations, namely, the prism resonator and unstable prism resonator, are demonstrated for the first time in an excimer (XeCl) laser with interesting and novel results. High misalignment tolerance ∼50 mrad is achieved with considerably reduced beam divergence of less than ∼1 mrad without reduction in output power capabilities of the laser. The misalignment tolerance of ∼50 mrad is a dramatic improvement of ∼25 times compared to ∼2 mrad normally observed in standard excimer laser with plane-plane cavity. Increase in depth of focus from 3 mm to 5.5 mm was also achieved in case of prism resonator configuration with an improvement of about 60%. Unstable prism resonator configuration is demonstrated here in this paper with further reduction in beam divergence to about 0.5 mrad using plano-convex lens as output coupler. The misalignment tolerance in case of unstable prism resonator was retained at about 30 mrad which is a high value compared to standard unstable resonators. The output beam spot was completely filled with flat-top profile with prism resonator configurations, which is desired for various material processing applications. Focusing properties and beam divergence in case of prism resonator have been investigated using SEM (scanning electron microscope) images. SEM images of the focused spot size (∼20 μm holes) on metal sheet indicate beam divergence of about 0.05 mrad which is about 1.5 times diffraction limit. Energy contained in this angle is thus sufficient for micro-machining applications. Clean and sharp edges of the micro-holes show high pointing stability with multiple shot exposures. Such characteristics of the excimer laser system will be extremely useful in micro-machining and other field applications.

On formation of a partially coherent beam in a stable-resonator laser

International Nuclear Information System (INIS)

Suvorov, A A

2010-01-01

A new method involving the expansion of the field coherence function in partially coherent modes - the eigensolutions of the problem for the second-order coherence function in a stable resonator - is proposed for the theoretical description of the process of multimode laser beam formation. The method for solving the problem for arbitrary partially coherent modes is formulated and the expressions for these modes are derived in the general form. The characteristics of the fundamental partially coherent mode, which coincides with the coherence function of a Gaussian partially coherent beam, are analysed in detail. The partially coherent modes are shown to possess two spatial scales - the effective radius and the coherence radius, which makes them a convenient tool for solving the problem of generation of a partially coherent beam. It is found that the unambiguous relation between the characteristics of partially coherent modes and the stable-resonator parameters is achieved by involving into consideration not only the process of the beam formation by the resonator mirrors but also the process of interaction of radiation with the active laser medium. (laser beams and resonators)

Effects of magnetic resonance-guided high-intensity focused ultrasound ablation on bone mechanical properties and modeling

NARCIS (Netherlands)

Yeoh, S.Y.; Arias Moreno, A.J.; Rietbergen, van B.; Hoeve, ter N.D.; Diest, van P.J.; Grull, H.

2015-01-01

Background Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) is a promising technique for palliative treatment of bone pain. In this study, the effects of MR-HIFU ablation on bone mechanics and modeling were investigated. Methods A total of 12 healthy rat femurs were ablated

Ultra-high brightness wavelength-stabilized kW-class fiber coupled diode laser

Science.gov (United States)

Huang, Robin K.; Chann, Bien; Glenn, John D.

2011-03-01

TeraDiode has produced a fiber-coupled direct diode laser with a power level of 1,040 W from a 200 μm core diameter, 0.18 numerical aperture (NA) output fiber at a single center wavelength. This was achieved with a novel beam combining and shaping technique using COTS diode lasers. The fiber-coupled output corresponds to a Beam Parameter Product (BPP) of 18 mm-mrad and is the lowest BPP kW-class direct diode laser yet reported. The laser has been used to demonstrate laser cutting and welding of steel sheet metal up to 6.65 mm thick. Further advances of these ultra-bright lasers are also projected.

A Coupled Resonator for Highly Tunable and Amplified Mixer/Filter

KAUST Repository

Ilyas, Saad; Jaber, Nizar; Younis, Mohammad I.

2017-01-01

We present an H-shaped resonator made of two clamped-clamped microbeams mechanically coupled at the middle with a strong coupler to achieve, in a single device, mechanical amplification of the response signal, filtering, and frequency conversion simultaneously. Using mechanical amplification combined with combination resonances generated from a mixed-frequency excitation, a wideband tunable filter, and a simultaneous frequency up and down convertors at multiple bands is demonstrated. The proposed coupled structure, when combined with the easy-to-implement technique of frequency mixing, is promising for applications in an RF chain.

A Coupled Resonator for Highly Tunable and Amplified Mixer/Filter

KAUST Repository

Ilyas, Saad

2017-04-25

We present an H-shaped resonator made of two clamped-clamped microbeams mechanically coupled at the middle with a strong coupler to achieve, in a single device, mechanical amplification of the response signal, filtering, and frequency conversion simultaneously. Using mechanical amplification combined with combination resonances generated from a mixed-frequency excitation, a wideband tunable filter, and a simultaneous frequency up and down convertors at multiple bands is demonstrated. The proposed coupled structure, when combined with the easy-to-implement technique of frequency mixing, is promising for applications in an RF chain.

Nonlinear dynamics in integrated coupled DFB lasers with ultra-short delay.

Science.gov (United States)

Liu, Dong; Sun, Changzheng; Xiong, Bing; Luo, Yi

2014-03-10

We report rich nonlinear dynamics in integrated coupled lasers with ultra-short coupling delay. Mutually stable locking, period-1 oscillation, frequency locking, quasi-periodicity and chaos are observed experimentally. The dynamic behaviors are reproduced numerically by solving coupled delay differential equations that take the variation of both frequency detuning and coupling phase into account. Moreover, it is pointed out that the round-trip frequency is not involved in the above nonlinear dynamical behaviors. Instead, the relationship between the frequency detuning Δν and the relaxation oscillation frequency νr under mutual injection are found to be critical for the various observed dynamics in mutually coupled lasers with very short delay.

Pfaffian Solutions and Resonant Interaction Properties of a Coupled BKP Lattice

International Nuclear Information System (INIS)

Zhao Hai-Qiong; Yu Guo-Fu

2014-01-01

In this paper, we give a coupled lattice equation with the help of Hirota operators, which comes from a special BKP lattice. Two-soliton and three-soliton solutions to the coupled system are constructed. Furthermore, resonant interaction of the two-soliton solution is analyzed in detail. Under some special resonant condition, it is shown that low soliton can propagate faster than high one. Finally, the N-soliton solution is presented in the Pfaffian form. (general)

Coupling constants deduced for the resonances in kaon photo-production

International Nuclear Information System (INIS)

Cheoun, M. K.; Kim, K. S.; Choi, T. K.

2004-01-01

We deduced the coupling constants of nucleon and hyperon resonances, which participate in kaon productions as intermediate states that are formed by electro-magnetic probes and that finally decay into hadronic final states. We used an isobaric model based on an effective Lagrangian approach to describe the processes, in which relevant coupling constants regarding related resonances are effectively determined by fitting available experimental data. Our scheme to deduce the coupling constants was as follows: First, we calculated the lower and the upper limits on the coupling constants by using the experimental decay data available until now and/or theoretical predictions, such as those from quark models and SU(3) symmetry. Second, we exploited those limits as physical constraints on our fitting scheme for the kaon photo-production data. Finally, the deduced values and regions of the coupling constants, which satisfy not only the reaction data but also the decay data, are presented as figures with respect to the strong and the electro-magnetic coupling constants, and their multiplicative values. Our results for the coupling constants give physical values that are more restricted than those allowed by the experimental data nowadays.

Comparing Laser Desorption Ionization and Atmospheric Pressure Photoionization Coupled to Fourier Transform Ion Cyclotron Resonance Mass Spectrometry To Characterize Shale Oils at the Molecular Level

Science.gov (United States)

Cho, Yunjo; Jin, Jang Mi; Witt, Matthias; Birdwell, Justin E.; Na, Jeong-Geol; Roh, Nam-Sun; Kim, Sunghwan

2013-01-01

Laser desorption ionization (LDI) coupled to Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to analyze shale oils. Previous work showed that LDI is a sensitive ionization technique for assessing aromatic nitrogen compounds, and oils generated from Green River Formation oil shales are well-documented as being rich in nitrogen. The data presented here demonstrate that LDI is effective in ionizing high-double-bond-equivalent (DBE) compounds and, therefore, is a suitable method for characterizing compounds with condensed structures. Additionally, LDI generates radical cations and protonated ions concurrently, the distribution of which depends upon the molecular structures and elemental compositions, and the basicity of compounds is closely related to the generation of protonated ions. This study demonstrates that LDI FT-ICR MS is an effective ionization technique for use in the study of shale oils at the molecular level. To the best of our knowledge, this is the first time that LDI FT-ICR MS has been applied to shale oils.

Are the same tapes really the same? Ultrasound study of laser-cut and mechanically cut TVT-O post-operative behavior.

Science.gov (United States)

Rusavy, Zdenek; Masata, Jaromir; Svabik, Kamil; Hubka, Petr; Zvara, Karel; Martan, Alois

2017-11-25

TVT-O production has been modified to laser cutting from mechanical cutting. We compared the behavior of laser and mechanically cut tension-free vaginal tape-obturator (TVT-O) using ultrasound at various time points after surgery. This is a retrospective analysis of clinical and ultrasound data from two previously reported randomized controlled trials with TVT-O. Behavior of mechanically cut TVT-O implanted in January 2007 to November 2009 and laser-cut TVT-O implanted in May 2010 to May 2012 was assessed by ultrasound at day 1, the 2nd week, the 3rd month, and the 1st and 2nd years post-operatively. Bladder neck and tape margins positions were described by coordinates in the orthogonal system calculated from polar coordinates. Tape mobility was measured as a change in the upper and lower tape margin position from rest to maximal Valsalva. Comparison of 2-year subjective and objective surgery outcomes was also performed. In total, 68 mechanically cut and 50 laser-cut TVT-Os were implanted. Follow-up data were available from 49 and 45 women respectively. No differences in any baseline characteristics or bladder neck mobility were observed. Significantly lower tape mobility was observed on day 1 and week 2 after mechanically cut TVT-O, although subsequent mobility was comparable to laser-cut TVT-O. The subjective and objective surgery outcomes were comparable. Although without clinical significance, early postoperative behavior of the mechanically cut and laser-cut TVT-O tapes differs. The less stiff, mechanically-cut TVT-O loosens within 2 weeks of implantation, whereas the stiffer, laser-cut TVT-O keeps its tension.

Numerical simulation of laser resonators

International Nuclear Information System (INIS)

Yoo, J. G.; Jeong, Y. U.; Lee, B. C.; Rhee, Y. J.; Cho, S. O.

2004-01-01

We developed numerical simulation packages for laser resonators on the bases of a pair of integral equations. Two numerical schemes, a matrix formalism and an iterative method, were programmed for finding numeric solutions to the pair of integral equations. The iterative method was tried by Fox and Li, but it was not applicable for high Fresnel numbers since the numerical errors involved propagate and accumulate uncontrollably. In this paper, we implement the matrix method to extend the computational limit further. A great number of case studies are carried out with various configurations of stable and unstable r;esonators to compute diffraction losses, phase shifts, intensity distributions and phases of the radiation fields on mirrors. Our results presented in this paper show not only a good agreement with the results previously obtained by Fox and Li, but also the legitimacy of our numerical procedures for high Fresnel numbers.

Mode Coupling and Nonlinear Resonances of MEMS Arch Resonators for Bandpass Filters

KAUST Repository

Hajjaj, Amal Z.

2017-01-30

We experimentally demonstrate an exploitation of the nonlinear softening, hardening, and veering phenomena (near crossing), where the frequencies of two vibration modes get close to each other, to realize a bandpass filter of sharp roll off from the passband to the stopband. The concept is demonstrated based on an electrothermally tuned and electrostatically driven MEMS arch resonator operated in air. The in-plane resonator is fabricated from a silicon-on-insulator wafer with a deliberate curvature to form an arch shape. A DC current is applied through the resonator to induce heat and modulate its stiffness, and hence its resonance frequencies. We show that the first resonance frequency increases up to twice of the initial value while the third resonance frequency decreases until getting very close to the first resonance frequency. This leads to the phenomenon of veering, where both modes get coupled and exchange energy. We demonstrate that by driving both modes nonlinearly and electrostatically near the veering regime, such that the first and third modes exhibit softening and hardening behavior, respectively, sharp roll off from the passband to the stopband is achievable. We show a flat, wide, and tunable bandwidth and center frequency by controlling the electrothermal actuation voltage.

Insufficient scientific evidence for efficacy of widely used electrotherapy, laser therapy, and ultrasound treatment in physiotherapy

NARCIS (Netherlands)

Bouter, L M

2000-01-01

The Dutch Health Council recently published a report on the efficacy of electrotherapy, laser therapy and ultrasound treatment for musculoskeletal disorders. The assessment was based on three systematic reviews, including 169 randomized clinical trials, and focused on a best-evidence synthesis.

Sensitivity Enhancement of Biochemical Sensors Based on Er+3 Doped Microsphere Coupled to an External Mirror

Directory of Open Access Journals (Sweden)

Alireza BAHRAMPOUR

2010-09-01

Full Text Available In this paper we proposed an active optical sensor designed based on the Er+3-doped microsphere coupled to an external mirror. The microsphere-mirror coupling causes the degeneracy splitting of the resonance frequencies. Each of resonance frequencies splits in to two different resonance frequencies .The coupling coefficient changes as a result of altering the refractive index of surrounding medium. So, the presence of bio/chemical analytes can be detected by measuring the change of laser output power, laser frequency or the difference between frequencies of the red and blue shifted modes. In the presence of mirror at least one order of magnitude sensitivity enhancement is obtained relative to the active microsphere biochemical sensors.

Coupling thermal atomic vapor to an integrated ring resonator

International Nuclear Information System (INIS)

Ritter, R; Kübler, H; Pfau, T; Löw, R; Gruhler, N; Pernice, W H P

2016-01-01

Strongly interacting atom–cavity systems within a network with many nodes constitute a possible realization for a quantum internet which allows for quantum communication and computation on the same platform. To implement such large-scale quantum networks, nanophotonic resonators are promising candidates because they can be scalably fabricated and interconnected with waveguides and optical fibers. By integrating arrays of ring resonators into a vapor cell we show that thermal rubidium atoms above room temperature can be coupled to photonic cavities as building blocks for chip-scale hybrid circuits. Although strong coupling is not yet achieved in this first realization, our approach provides a key step towards miniaturization and scalability of atom–cavity systems. (paper)

Tunable superconducting resonators with integrated trap structures for coupling with ultracold atomic gases

Energy Technology Data Exchange (ETDEWEB)

Ferdinand, Benedikt; Wiedmaier, Dominik; Koelle, Dieter; Kleiner, Reinhold [Physikalisches Institut and Center for Quantum Science in LISA+, Universitaet Tuebingen (Germany); Bothner, Daniel [Physikalisches Institut and Center for Quantum Science in LISA+, Universitaet Tuebingen (Germany); Kavli Institute of Nanoscience, Delft University of Technology, Delft (Netherlands)

2016-07-01

We intend to investigate a hybrid quantum system where ultracold atomic gases play the role of a long-living quantum memory, coupled to a superconducting qubit via a coplanar waveguide transmission line resonator. As a first step we developed a resonator chip containing a Z-shaped trapping wire for the atom trap. In order to suppress parasitic resonances due to stray capacitances, and to achieve good ground connection we use hybrid superconductor - normal conductor chips. As an additional degree of freedom we add a ferroelectric capacitor making the resonators voltage-tunable. We furthermore show theoretical results on the expected coupling strength between resonator and atomic cloud.

Dynamics of multi-frequency oscillator ensembles with resonant coupling

Science.gov (United States)

Lück, S.; Pikovsky, A.

2011-07-01

We study dynamics of populations of resonantly coupled oscillators having different frequencies. Starting from the coupled van der Pol equations we derive the Kuramoto-type phase model for the situation, where the natural frequencies of two interacting subpopulations are in relation 2:1. Depending on the parameter of coupling, ensembles can demonstrate fully synchronous clusters, partial synchrony (only one subpopulation synchronizes), or asynchrony in both subpopulations. Theoretical description of the dynamics based on the Watanabe-Strogatz approach is developed.

Influence of resonator length on catastrophic optical damage in high-power AlGaInP broad-area lasers

Science.gov (United States)

Bou Sanayeh, Marwan

2017-05-01

The increasing importance of extracting high optical power out of semiconductor lasers motivated several studies in catastrophic optical damage (COD) level improvement. In this study, the influence of the resonator length in high-power broad-area (BA) AlGaInP lasers on COD is presented. For the analyses, several 638 nm AlGaInP 60 μm BA lasers from the same wafer were used. Resonator lengths of 900, 1200, 1500, and 1800 μm were compared. In order to independently examine the effect of the resonator length on the maximum power reached by the lasers before COD (PCOD), the lasers used are uncoated and unmounted, and PCOD under pulsed mode was determined. It was found that higher output powers and eventually higher PCOD can be achieved using longer resonators; however, it was also found that this is mainly useful when working at high output powers far away from the laser threshold, since the threshold current and slope efficiency worsen when the resonator length increases.

Laser ultrasound and simulated time reversal on bulk waves for non destructive control

International Nuclear Information System (INIS)

Diot, G; Walaszek, H; Kouadri-David, A; Guégan, S; Flifla, J

2014-01-01

Laser welding of aluminium generally creates embedded welding defects, such as porosities or cracks. Non Destructive Inspection (NDI) after processing may ensure an acceptable weld quality by defect detection. Nowadays, NDI techniques used to control the inside of a weld are mainly limited to X-Rays or ultrasonics. The current paper describes the use of a Laser Ultrasound (LU) technique to inspect porosities in 2 and 4-mm thick sheet lap welds. First experimentations resulted in the detection of 0.5-mm drilled holes in bulk aluminium sheets. The measurement of the depth of these defects is demonstrated too. Further experimentations shows the applicability of the LU technique to detect porosities in aluminium laser welds. However, as the interpretation of raw measures is limiting the detection capacity of this technique, we developed a signal processing using Time-Reversal capabilities to enhance detection capacities. Furthermore, the signal processing output is a geometrical image of the material's inner state, increasing the ease of interpretation. It is based on a mass-spring simulation which enables the back-propagation of the acquired ultrasound signal. The spring-mass simulation allows the natural generation of all the different sound waves and thus enables the back-propagation of a raw signal without any need of filtering or wave identification and extraction. Therefore the signal processing uses the information contained in the compression wave as well as in the shear wave

Wavelength scaling of laser plasma coupling

International Nuclear Information System (INIS)

Kruer, W.L.

1983-01-01

The use of shorter wavelength laser light both enhances collisional absorption and reduces deleterious collective plasma effects. Coupling processes which can be important in reactor-size targets are briefly reviewed. Simple estimates are presented for the intensity-wavelength regime in which collisional absorption is high and collective effects are minimized

What does magnetic resonance imaging add to the prenatal ultrasound diagnosis of facial clefts?

Science.gov (United States)

Mailáth-Pokorny, M; Worda, C; Krampl-Bettelheim, E; Watzinger, F; Brugger, P C; Prayer, D

2010-10-01

Ultrasound is the modality of choice for prenatal detection of cleft lip and palate. Because its accuracy in detecting facial clefts, especially isolated clefts of the secondary palate, can be limited, magnetic resonance imaging (MRI) is used as an additional method for assessing the fetus. The aim of this study was to investigate the role of fetal MRI in the prenatal diagnosis of facial clefts. Thirty-four pregnant women with a mean gestational age of 26 (range, 19-34) weeks underwent in utero MRI, after ultrasound examination had identified either a facial cleft (n = 29) or another suspected malformation (micrognathia (n = 1), cardiac defect (n = 1), brain anomaly (n = 2) or diaphragmatic hernia (n = 1)). The facial cleft was classified postnatally and the diagnoses were compared with the previous ultrasound findings. There were 11 (32.4%) cases with cleft of the primary palate alone, 20 (58.8%) clefts of the primary and secondary palate and three (8.8%) isolated clefts of the secondary palate. In all cases the primary and secondary palate were visualized successfully with MRI. Ultrasound imaging could not detect five (14.7%) facial clefts and misclassified 15 (44.1%) facial clefts. The MRI classification correlated with the postnatal/postmortem diagnosis. In our hands MRI allows detailed prenatal evaluation of the primary and secondary palate. By demonstrating involvement of the palate, MRI provides better detection and classification of facial clefts than does ultrasound alone. Copyright © 2010 ISUOG. Published by John Wiley & Sons, Ltd.

Effects of laser beam propagation in a multilevel photoionization system

International Nuclear Information System (INIS)

Izawa, Y.; Nomaru, K.; Chen, Y. W.

1995-01-01

When the intense laser pulse propagates in the atomic vapor over a long distance, the laser pulse shape, the carrier frequency and the propagating velocity are greatly modified during the propagation by the resonant and/or the near-resonant interactions with atoms. We have been investigating these effects on the laser beam propagation experimentally and analytically. The simulation code named CEALIS-P has been developed, which employs the coupled three- level Bloch-Maxwell equations to study the atomic excitation and laser beam propagation simultaneously. Several features of the resonant and near-resonant effects based on the the self-induced transparency, the self-phase modulation and the nonlinear group velocity dispersion are described and the influences of such effects on the photoionization efficiency are analyzed.

Stochastic resonance in multi-stable coupled systems driven by two driving signals

Science.gov (United States)

Xu, Pengfei; Jin, Yanfei

2018-02-01

The stochastic resonance (SR) in multi-stable coupled systems subjected to Gaussian white noises and two different driving signals is investigated in this paper. Using the adiabatic approximation and the perturbation method, the coupled systems with four-well potential are transformed into the master equations and the amplitude of the response is obtained. The signal-to-noise ratio (SNR) is calculated numerically to demonstrate the occurrence of SR. For the case of two driving signals with different amplitudes, the interwell resonance between two wells S1 and S3 emerges for strong coupling. The SR can appear in the subsystem with weaker signal amplitude or even without driving signal with the help of coupling. For the case of two driving signals with different frequencies, the effects of SR in two subsystems driven by high and low frequency signals are both weakened with an increase in coupling strength. The stochastic multi-resonance phenomenon is observed in the subsystem subjected to the low frequency signal. Moreover, an effective scheme for phase suppressing SR is proposed by using a relative phase between two driving signals.

Single and Coupled Nanobeam Cavities

DEFF Research Database (Denmark)

Ivinskaya, Aliaksandra; Lavrinenko, Andrei; Shyroki, Dzmitry M.

2013-01-01

for analysis and design of photonic crystal devices, such as 2D ring resonators for filters, single and coupled nanobeam cavities, birefringence in photonic crystal cavities, threshold analysis in photonic crystal lasers, gap solitons in photonic crystals, novel photonic atolls, dynamic characteristics...

Optical phase dynamics in mutually coupled diode laser systems exhibiting power synchronization

International Nuclear Information System (INIS)

Pal, Vishwa; Ghosh, R; Prasad, Awadhesh

2011-01-01

We probe the physical mechanism behind the known phenomenon of power synchronization of two diode lasers that are mutually coupled via their delayed optical fields. In a diode laser, the amplitude and the phase of the optical field are coupled by the so-called linewidth enhancement factor, α. In this work, we explore the role of optical phases of the electric fields in amplitude (and hence power) synchronization through α in such mutually delay-coupled diode laser systems. Our numerical results show that the synchronization of optical phases drives the powers of lasers to synchronized death regimes. We also find that as α varies for different diode lasers, the system goes through a sequence of in-phase amplitude-death states. Within the windows between successive amplitude-death regions, the cross-correlation between the field amplitudes exhibits a universal power-law behaviour with respect to α.

700 W blue fiber-coupled diode-laser emitting at 450 nm

Science.gov (United States)

Balck, A.; Baumann, M.; Malchus, J.; Chacko, R. V.; Marfels, S.; Witte, U.; Dinakaran, D.; Ocylok, S.; Weinbach, M.; Bachert, C.; Kösters, A.; Krause, V.; König, H.; Lell, A.; Stojetz, B.; Löffler, A.; Strauss, U.

2018-02-01

A high-power blue laser source was long-awaited for processing materials with low absorption in the near infrared (NIR) spectral range like copper or gold. Due to the huge progress of GaN-based semiconductors, the performance of blue diode-lasers has made a major step forward recently. With the availability of unprecedented power levels at cw-operating blue diode-lasers emitting at 450 nm, it was possible to set up a high-power diode-laser in the blue spectral range to address these conventional laser applications and probably beyond that to establish completely new utilizations for lasers. Within the scope of the research project "BlauLas", funded within the German photonic initiative "EFFILAS" [8] by the German Federal Ministry of Education and Research (BMBF), Laserline in cooperation with OSRAM aims to realize a cw fiber-coupled diode-laser exceeding 1 kW blue laser power. In this paper the conceptual design and experimental results of a 700 W blue fiber-coupled diode-laser are presented. Initially a close look had to be taken on the mounting techniques of the semiconductors to serve the requirements of the GaN laser diodes. Early samples were used for extensive long term tests to investigate degradation processes. With first functional laser-modules we set up fiber-coupled laser-systems for further testing. Besides adaption of well-known optical concepts a main task within the development of the laser system was the selection and examination of suitable materials and assembling in order to minimize degradation and reach adequate lifetimes. We realized R&D blue lasersystems with lifetimes above 5,000 h, which enable first application experiments on processing of various materials as well as experiments on conversion to white-light.

Ultrasound-guided interstitial laser photocoagulation of an autonomous thyroid nodule

DEFF Research Database (Denmark)

Døssing, Helle; Bennedbaek, Finn Noe; Hegedüs, Laszlo

2003-01-01

effects and often necessitates multiple treatment sessions. We present a case of a 17-year-old female successfully treated with ultrasound (US)-guided percutaneous interstitial laser photocoagulation (ILP) for an AFTN. Initially, she had a serum thyrotropin (TSH) of 0.01 mU/L and normal peripheral thyroid.......9 mL (40% reduction) without further alterations during an additional 9 months of follow-up. Side effects were transient thyrotoxicosis and local pain as seen with PEI. To our knowledge, this is the first reported case of ILP used in a patient with a pretoxic thyroid nodule. US-guided thermic tissue...

Rapid determination of the volatile components in tobacco by ultrasound-microwave synergistic extraction coupled to headspace solid-phase microextraction with gas chromatography-mass spectrometry.

Science.gov (United States)

Yang, Yanqin; Chu, Guohai; Zhou, Guojun; Jiang, Jian; Yuan, Kailong; Pan, Yuanjiang; Song, Zhiyu; Li, Zuguang; Xia, Qian; Lu, Xinbo; Xiao, Weiqiang

2016-03-01

An ultrasound-microwave synergistic extraction coupled to headspace solid-phase microextraction was first employed to determine the volatile components in tobacco samples. The method combined the advantages of ultrasound, microwave, and headspace solid-phase microextraction. The extraction, separation, and enrichment were performed in a single step, which could greatly simplify the operation and reduce the whole pretreatment time. In the developed method, several experimental parameters, such as fiber type, ultrasound power, and irradiation time, were optimized to improve sampling efficiency. Under the optimal conditions, there were 37, 36, 34, and 36 components identified in tobacco from Guizhou, Hunan, Yunnan, and Zimbabwe, respectively, including esters, heterocycles, alkanes, ketones, terpenoids, acids, phenols, and alcohols. The compound types were roughly the same while the contents were varied from different origins due to the disparity of their growing conditions, such as soil, water, and climate. In addition, the ultrasound-microwave synergistic extraction coupled to headspace solid-phase microextraction method was compared with the microwave-assisted extraction coupled to headspace solid-phase microextraction and headspace solid-phase microextraction methods. More types of volatile components were obtained by using the ultrasound-microwave synergistic extraction coupled to headspace solid-phase microextraction method, moreover, the contents were high. The results indicated that the ultrasound-microwave synergistic extraction coupled to headspace solid-phase microextraction technique was a simple, time-saving and highly efficient approach, which was especially suitable for analysis of the volatile components in tobacco. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Resonant laser mass spectrometry for environmental and industrial chemical trace analysis

International Nuclear Information System (INIS)

Boesl, Ulrich; Rink, Joerg; Distelrath, Volker; Pueffel, Peter

2001-01-01

A promising new method for pollutant trace analysis is resonant laser mass spectrometry. It combines selectivity, sensitivity, and speed of measurement. In this paper, two examples of application are presented: exhaust analysis of combustion engines and analysis of polycylcic aromatic compounds in soil samples. The sensitivity of small, mobile instruments is discussed as well as alternative laser-based techniques in the case formation of cations by nanosecond lasers is improbable

Time-resolved resonance fluorescence spectroscopy for study of chemical reactions in laser-induced plasmas.

Science.gov (United States)

Liu, Lei; Deng, Leimin; Fan, Lisha; Huang, Xi; Lu, Yao; Shen, Xiaokang; Jiang, Lan; Silvain, Jean-François; Lu, Yongfeng

2017-10-30

Identification of chemical intermediates and study of chemical reaction pathways and mechanisms in laser-induced plasmas are important for laser-ablated applications. Laser-induced breakdown spectroscopy (LIBS), as a promising spectroscopic technique, is efficient for elemental analyses but can only provide limited information about chemical products in laser-induced plasmas. In this work, time-resolved resonance fluorescence spectroscopy was studied as a promising tool for the study of chemical reactions in laser-induced plasmas. Resonance fluorescence excitation of diatomic aluminum monoxide (AlO) and triatomic dialuminum monoxide (Al 2 O) was used to identify these chemical intermediates. Time-resolved fluorescence spectra of AlO and Al 2 O were used to observe the temporal evolution in laser-induced Al plasmas and to study their formation in the Al-O 2 chemistry in air.

Fast Resonance Raman Spectroscopy of a Free Radical

DEFF Research Database (Denmark)

Wilbrandt, Robert Walter; Pagsberg, Palle Bjørn; Hansen, K. B.

1975-01-01

The resonance Raman spectrum of a 10−3 molar solution of the stable diphenyl-pikryl-hydrazyl radical in benzene was obtained using a single laser pulse of 10 mJ energy and 600 ns duration from a flashlamp pumped tunable dye laser. Spectra were recorded using an image intensifier coupled to a TV...

Photonic crystal Fano lasers and Fano switches

DEFF Research Database (Denmark)

Mørk, Jesper; Yu, Yi; Bekele, Dagmawi Alemayehu

2017-01-01

We show that Fano resonances can be realized in photonic crystal membrane structures by coupling line-defect waveguides and point-defect nanocavities. The Fano resonance can be exploited to realize optical switches with very small switching energy, as well as Fano lasers, that can generate short...

High coupling efficiency of foam spherical hohlraum driven by 2ω laser light

Science.gov (United States)

Chen, Yao-Hua; Lan, Ke; Zheng, Wanguo; Campbell, E. M.

2018-02-01

The majority of solid state laser facilities built for laser fusion research irradiate targets with third harmonic light (0.35 μm) up-converted from the fundamental Nd wavelength at 1.05 μm. The motivation for this choice of wavelength is improved laser-plasma coupling. Significant disadvantages to this choice of wavelength are the reduced damage threshold of optical components and the efficiency of energy conversion to third harmonic light. Both these issues are significantly improved if second harmonic (0.53 μm) radiation is used, but theory and experiments have shown lower optical to x-ray energy conversion efficiency and increased levels of laser-plasma instabilities, resulting in reduced laser-target coupling. In this letter, we propose to use a 0.53 μm laser for the laser ignition facilities and use a low density foam wall to increase the coupling efficiency from the laser to the capsule and present two-dimensional radiation-hydrodynamic simulations of 0.53 μm laser light irradiating an octahedral-spherical hohlraum with a low density foam wall. The simulations show that the reduced optical depth of the foam wall leads to an increased laser-light conversion into thermal x-rays and about 10% higher radiation flux on the capsule than that achieved with 0.35 μm light irradiating a solid density wall commonly used in laser indirect drive fusion research. The details of the simulations and their implications and suggestions for wavelength scaling coupled with innovative hohlraum designs will be discussed.

Hepatocellular adenoma: findings at state-of-the-art magnetic resonance imaging, ultrasound, computed tomography and pathologic analysis

International Nuclear Information System (INIS)

Hussain, Shahid M.; Bos, Indra C. van den; Dwarkasing, Roy S.; Kuiper, Jan-Willem; Hollander, Jan den

2006-01-01

The purpose of this paper is to describe the most recent concepts and pertinent findings of hepatocellular adenomas, including clinical presentation, gross pathology and histology, pathogenesis and transformation into hepatocellular carcinoma (HCC), and imaging findings at ultrasound (US), computed tomography (CT), and magnetic resonance (MR) imaging. (orig.)

Resonance ionization in a gas cell: a feasibility study for a laser ion source

International Nuclear Information System (INIS)

Qamhieh, Z.N.; Vandeweert, E.; Silverans, R.E.; Duppen, P. van; Huyse, M.; Vermeeren, L.

1992-01-01

A laser ion source based on resonance photo-ionization in a gas cell is proposed. The gas cell, filled with helium, consists of a target chamber in which the recoil products are stopped and neutralized, and an ionization chamber where the atoms of interest are selectively ionized by the laser light. The extraction of the ions from the ionization chamber through the exit hole-skimmer setup is similar to the ion-guide system. The conditions to obtain an optimal system are given. The results of a two-step one-laser resonance photo-ionization of nickel and the first results of laser ionization in a helium buffer gas cell are presented. (orig.)

Radiative resonance couplings in γ π →π π

Science.gov (United States)

Hoferichter, Martin; Kubis, Bastian; Zanke, Marvin

2017-12-01

Studies of the reaction γ π →π π , in the context of the ongoing Primakoff program of the COMPASS experiment at CERN, give access to the radiative couplings of the ρ (770 ) and ρ3(1690 ) resonances. We provide a vector-meson-dominance estimate of the respective radiative width of the ρ3, Γρ3→πγ=48 (18 ) keV , as well as its impact on the F -wave in γ π →π π . For the ρ (770 ), we establish the formalism necessary to extract its radiative coupling directly from the residue of the resonance pole by analytic continuation of the γ π →π π amplitude to the second Riemann sheet, without any reference to the vector-meson-dominance hypothesis.

A MEMS coupled resonator for frequency filtering in air

KAUST Repository

Ilyas, Saad

2018-02-03

We present design, fabrication, and characterization of a mechanically coupled MEMS H resonator capable of performing simultaneous mechanical amplification and filtering in air. The device comprises of two doubly clamped polyimide microbeams joined through the middle by a coupling beam of the same size. The resonator is fabricated via a multi-layer surface micromachining process. A special fabrication process and device design is employed to enable operation in air and to achieve mechanical amplification of the output response. Moreover, mixed-frequency excitation is used to demonstrate a tunable wide band filter for low frequency applications. It is demonstrated that through the multi-source harmonic excitation and the operation in air, an improved band-pass filter with flat response and minimal ripples can be achieved.

Tunneling effect in cavity-resonator-coupled arrays

International Nuclear Information System (INIS)

Ma Hua; Xu Zhuo; Qu Shao-Bo; Zhang Jie-Qiu; Wang Jia-Fu; Liang Chang-Hong

2013-01-01

The quantum tunneling effect (QTE) in a cavity-resonator-coupled (CRC) array was analytically and numerically investigated. The underlying mechanism was interpreted by treating electromagnetic waves as photons, and then was generalized to acoustic waves and matter waves. It is indicated that for the three kinds of waves, the QTE can be excited by cavity resonance in a CRC array, resulting in sub-wavelength transparency through the narrow splits between cavities. This opens up opportunities for designing new types of crystals based on CRC arrays, which may find potential applications such as quantum devices, micro-optic transmission, and acoustic manipulation. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Effect of vapor plasma on the coupling of laser radiation with aluminum targets

Energy Technology Data Exchange (ETDEWEB)

Shui, V H; Kivel, B; Weyl, G M

1978-12-01

The effect of vapor plasma on thermal and impulse coupling of laser radiation with aluminum targets is studied to understand and explain experimental data showing anomalously high coupling to 10.6-micron laser radiation. Heating of vapor by inverse bremsstrahlung absorption of laser radiation, subsequent reradiation in the uv and deep uv by ionized species, and vapor layer growth are modeled. A computer code has been developed to solve the governing equations. Major conclusions include the following: (1) vapor plasma radiative transport can be an important mechanism for laser/target coupling, (2) aluminum vapor (density times thickness) approximately equal to 10 to the 17th power/sq cm (corresponding to about 0.01 micron of target material) can result in thermal coupling coefficients of 20% or more, and (3) too much vapor reduces the net flux at the target.

Resonant ablation of single-wall carbon nanotubes by femtosecond laser pulses

International Nuclear Information System (INIS)

Arutyunyan, N R; Komlenok, M S; Kononenko, V V; Pashinin, V P; Pozharov, A S; Konov, V I; Obraztsova, E D

2015-01-01

The thin 50 nm film of bundled arc-discharge single-wall carbon nanotubes was irradiated by femtosecond laser pulses with wavelengths 675, 1350 and 1745 nm corresponding to the absorption band of metallic nanotubes E 11 M , to the background absorption and to the absorption band of semiconducting nanotubes E 11 S , respectively. The aim was to induce a selective removal of nanotubes of specific type from the bundled material. Similar to conducted thermal heating experiments, the effect of laser irradiation results in suppression of all radial breathing modes in the Raman spectra, with preferential destruction of the metallic nanotubes with diameters less than 1.26 nm and of the semiconducting nanotubes with diameters 1.36 nm. However, the etching rate of different nanotubes depends on the wavelength of the laser irradiation. It is demonstrated that the relative content of nanotubes of different chiralities can be tuned by a resonant laser ablation of undesired nanotube fraction. The preferential etching of the resonant nanotubes has been shown for laser wavelengths 675 nm (E 11 M ) and 1745 nm (E 11 S ). (paper)

Ultrasound/Magnetic Resonance Image Fusion Guided Lumbosacral Plexus Block – A Clinical Study

DEFF Research Database (Denmark)

Strid, JM; Pedersen, Erik Morre; Søballe, Kjeld

2014-01-01

in a double-blinded randomized controlled trial with crossover design. MR datasets will be acquired and uploaded in an advanced US system (Epiq7, Phillips, Amsterdam, Netherlands). All volunteers will receive SSPS blocks with lidocaine added gadolinium contrast guided by US/MR image fusion and by US one week......Background and aims Ultrasound (US) guided lumbosacral plexus block (Supra Sacral Parallel Shift [SSPS]) offers an alternative to general anaesthesia and perioperative analgesia for hip surgery.1 The complex anatomy of the lumbosacral region hampers the accuracy of the block, but it may be improved...... by guidance of US and magnetic resonance (MR) image fusion and real-time 3D electronic needle tip tracking.2 We aim to estimate the effect and the distribution of lidocaine after SSPS guided by US/MR image fusion compared to SSPS guided by ultrasound. Methods Twenty-four healthy volunteers will be included...

The Harmonically Coupled 2-Beam FEL

CERN Document Server

McNeil, Brian W J

2004-01-01

A 1-D model of a 2-beam Free Electron Laser amplifier is presented. The two co-propagating electron beams have different energies, chosen so that the fundamental resonant FEL interaction of the higher energy beam is at an harmonic of the lower energy beam. In this way, a coupling between the FEL interactions of the two beams occurs via the harmonic components of the electron bunching and radiation emission of the lower energy interaction. Such resonantly coupled FEL interactions may offer potential benefits over existing single beam FEL schemes. A simple example is presented where the lower energy FEL interaction only is seeded with radiation at its fundamental resonant wavelength. It is predicted that the coherence properties of this seed field are transfered via the resonantly coupled FEL interaction to the un-seeded higher energy FEL interaction, thereby improving its coherence properties over that of a SASE interaction alone. This method may offer an alternative seeding scheme for FELs operating in the XU...

Heterodyne interferometer laser source with a pair of two phase locked loop coupled He–Ne lasers by 632.8 nm

International Nuclear Information System (INIS)

Sternkopf, C; Diethold, C; Gerhardt, U; Manske, E; Wurmus, J

2012-01-01

Two He–Ne lasers are frequency and phase coupled by phase locking loop technique for a heterodyne laser interferometer. The heterodyne He–Ne laser is built of stabilized commercially used laser tubes. The two lasers create a high frequency stable heterodyne laser source with an output power of 2 mW. The laser source is coupled by two fibers (one fiber per laser) to the heterodyne laser head. This paper describes the configuration and the control theory basics of the laser system. The experimental setup and the equipment used are also described. First, experimental results with different parameters are represented. Then we discuss a novel heterodyne laser source which has achieved a master laser frequency stability of Δf 1 /f 1 = 1 · 10 −8 and a beat frequency stability of approximately Δf beat /f beat ≈ 4.5 · 10 −5 . (paper)

Ferro-paramagnetic coupled resonant modes in GdEuCuO4

International Nuclear Information System (INIS)

Fainstein, A.; Tovar, M.

1990-01-01

Two paramagnetic resonances were observed in compound GdEuCuO 4 : one was originated in trivalent gadolinium paramagnetism, while the other is associated to a weak ferromagnetic mode in Cu-O planes. In this work, experimental results are presented that show an anisotropy and a strongly anomalous temperature dependence of Gd 3+ . A theoretical model was introduced which explains the data in terms of coupled ferro-paramagnetic resonant modes originated in spin exchange coupling of Cu and Gd. (Author). 9 refs., 4 figs

Babinet principle and diffraction losses in laser resonators

International Nuclear Information System (INIS)

Kubarev, V V

2000-01-01

A simple analytical technique, based on the Babinet principle, for calculating low diffraction losses of different kinds in stable resonators is described. The technique was verified by comparison with the known numerical and analytical calculations of the losses in specific diffraction problems. (laser applications and other topics in quantum electronics)

Magnetic resonance imaging-guided focused ultrasound to increase localized blood-spinal cord barrier permeability.

Science.gov (United States)

Payne, Allison H; Hawryluk, Gregory W; Anzai, Yoshimi; Odéen, Henrik; Ostlie, Megan A; Reichert, Ethan C; Stump, Amanda J; Minoshima, Satoshi; Cross, Donna J

2017-12-01

Spinal cord injury (SCI) affects thousands of people every year in the USA, and most patients are left with some permanent paralysis. Therapeutic options are limited and only modestly affect outcome. To address this issue, we used magnetic resonance imaging-guided focused ultrasound (MRgFUS) as a non-invasive approach to increase permeability in the blood-spinal cord barrier (BSCB). We hypothesize that localized, controlled sonoporation of the BSCB by MRgFUS will aid delivery of therapeutics to the injury. Here, we report our preliminary findings for the ability of MRgFUS to increase BSCB permeability in the thoracic spinal cord of a normal rat model. First, an excised portion of normal rat spinal column was used to characterize the acoustic field and to estimate the insertion losses that could be expected in an MRgFUS blood spinal cord barrier opening. Then, in normal rats, MRgFUS was applied in combination with intravenously administered microbubbles to the spinal cord region. Permeability of the BSCB was indicated as signal enhancement by contrast administered prior to T1-weighted magnetic resonance imaging and verified by Evans blue dye. Neurological testing using the Basso, Beattie, and Breshnahan scale and the ladder walk was normal in 8 of 10 rats tested. Two rats showed minor impairment indicating need for further refinement of parameters. No gross tissue damage was evident by histology. In this study, we have opened successfully the blood spinal cord barrier in the thoracic region of the normal rat spine using magnetic resonance-guided focused ultrasound combined with microbubbles.

Advanced methods for nuclear reactor gas laser coupling

International Nuclear Information System (INIS)

Miley, G.H.; Verdeyen, J.T.

1978-06-01

Research is described that led to the discovery of three nuclear-pumped lasers (NPLs) using mixtures of Ne--N 2 , He--Hg, and He or Ne with CO or CO 2 . The Ne--N 2 NPL was the first laser obtained with modest neutron fluxes from a TRIGA reactor (vs fast burst reactors used elsewhere in such work), the He--Hg NPL was the first visible nuclear-pumped laser, while the Ne--CO and He--CO 2 lasers are the first to provide energy storage on a millisecond time scale. Important potential applications of NPLs include coupling and power transmission from remote power stations such as nuclear plants in satellites and neutron-feedback operation of inertial confinement fusion plants

Photoionization of resonantly driven atomic states by an extreme ultraviolet-free-electron laser: intensity dependence and renormalization of Rabi frequencies

International Nuclear Information System (INIS)

Kaiser, B; Brand, A; Glässl, M; Vagov, A; Axt, V M; Pietsch, U

2013-01-01

We analyze theoretically the high intensity photoionization dynamics of a system with two atomic states resonantly coupled by coherent extreme ultraviolet laser radiation that also gives rise to the ionization. The ground state occupation of such a system is shown to exhibit damped Rabi oscillations. The corresponding ionization, which is responsible for the damping, scales almost linearly with the field intensity when the pulse length exceeds the Rabi period. For shorter pulses a quadratic scaling is found. The Rabi frequency is shifted compared to its value for an isolated two-level system. The shift increases with excitation intensity and can acquire a high percentage of the unrenormalized frequency at high intensities. Analytical results obtained within a simplified solvable model demonstrate that the damping and the shift both result from the coupling of the discrete states to the ionization continuum and are therefore closely related. Numerical simulations for a two-electron system reveal at high intensities the importance of off-resonant ionization channels. (paper)

All-metal coupling and package of semiconductor laser and amplifier with optical fiber

International Nuclear Information System (INIS)

Xu Fenglan; Li Lina; Zhang Yueqing

1992-01-01

The semiconductor laser and optical amplifier made by Changchun Institute of Physics coupled with optical fiber by use of all-metal coupling are represented. The net gain of semiconductor laser amplifier with optical fiber is 14 ∼18 dB

Anisotropic magnetocrystalline coupling of the skyrmion lattice in MnSi

Science.gov (United States)

Luo, Yongkang; Lin, Shi-Zeng; Fobes, D. M.; Liu, Zhiqi; Bauer, E. D.; Betts, J. B.; Migliori, A.; Thompson, J. D.; Janoschek, M.; Maiorov, B.

2018-03-01

We investigate the anisotropic nature of magnetocrystalline coupling between the crystallographic and skyrmion crystal (SKX) lattices in the chiral magnet MnSi by magnetic field-angle resolved resonant ultrasound spectroscopy. Abrupt changes are observed in the elastic moduli and attenuation when the magnetic field is parallel to the [011] crystallographic direction. These observations are interpreted in a phenomenological Ginzburg-Landau theory that identifies switching of the SKX orientation to be the result of an anisotropic magnetocrystalline coupling potential. Our paper sheds new light on the nature of magnetocrystalline coupling potential relevant to future spintronic applications.

An All-Solid-State High Repetiton Rate Titanium:Sapphire Laser System For Resonance Ionization Laser Ion Sources

Science.gov (United States)

Mattolat, C.; Rothe, S.; Schwellnus, F.; Gottwald, T.; Raeder, S.; Wendt, K.

2009-03-01

On-line production facilities for radioactive isotopes nowadays heavily rely on resonance ionization laser ion sources due to their demonstrated unsurpassed efficiency and elemental selectivity. Powerful high repetition rate tunable pulsed dye or Ti:sapphire lasers can be used for this purpose. To counteract limitations of short pulse pump lasers, as needed for dye laser pumping, i.e. copper vapor lasers, which include high maintenance and nevertheless often only imperfect reliability, an all-solid-state Nd:YAG pumped Ti:sapphire laser system has been constructed. This could complement or even replace dye laser systems, eliminating their disadvantages but on the other hand introduce shortcomings on the side of the available wavelength range. Pros and cons of these developments will be discussed.

Air-coupled ultrasonic through-transmission thickness measurements of steel plates.

Science.gov (United States)

Waag, Grunde; Hoff, Lars; Norli, Petter

2015-02-01

Non-destructive ultrasonic testing of steel structures provide valuable information in e.g. inspection of pipes, ships and offshore structures. In many practical applications, contact measurements are cumbersome or not possible, and air-coupled ultrasound can provide a solution. This paper presents air-coupled ultrasonic through-transmission measurements on a steel plate with thicknesses 10.15 mm; 10.0 mm; 9.8 mm. Ultrasound pulses were transmitted from a piezoelectric transducer at normal incidence, through the steel plate, and were received at the opposite side. The S1, A2 and A3 modes of the plate are excited, with resonance frequencies that depend on the material properties and the thickness of the plate. The results show that the resonances could be clearly identified after transmission through the steel plate, and that the frequencies of the resonances could be used to distinguish between the three plate thicknesses. The S1-mode resonance was observed to be shifted 10% down compared to a simple plane wave half-wave resonance model, while the A2 and S2 modes were found approximately at the corresponding plane-wave resonance frequencies. A model based on the angular spectrum method was used to predict the response of the through-transmission setup. This model included the finite aperture of the transmitter and receiver, and compressional and shear waves in the solid. The model predicts the frequencies of the observed modes of the plate to within 1%, including the down-shift of the S1-mode. Copyright © 2014 Elsevier B.V. All rights reserved.

Imaging of plantar fascia disorders: findings on plain radiography, ultrasound and magnetic resonance imaging.

Science.gov (United States)

Draghi, Ferdinando; Gitto, Salvatore; Bortolotto, Chandra; Draghi, Anna Guja; Ori Belometti, Gioia

2017-02-01

Plantar fascia (PF) disorders commonly cause heel pain and disability in the general population. Imaging is often required to confirm diagnosis. This review article aims to provide simple and systematic guidelines for imaging assessment of PF disease, focussing on key findings detectable on plain radiography, ultrasound and magnetic resonance imaging (MRI). Sonographic characteristics of plantar fasciitis include PF thickening, loss of fibrillar structure, perifascial collections, calcifications and hyperaemia on Doppler imaging. Thickening and signal changes in the PF as well as oedema of adjacent soft tissues and bone marrow can be assessed on MRI. Radiographic findings of plantar fasciitis include PF thickening, cortical irregularities and abnormalities in the fat pad located deep below the PF. Plantar fibromatosis appears as well-demarcated, nodular thickenings that are iso-hypoechoic on ultrasound and show low-signal intensity on MRI. PF tears present with partial or complete fibre interruption on both ultrasound and MRI. Imaging description of further PF disorders, including xanthoma, diabetic fascial disease, foreign-body reactions and plantar infections, is detailed in the main text. Ultrasound and MRI should be considered as first- and second-line modalities for assessment of PF disorders, respectively. Indirect findings of PF disease can be ruled out on plain radiography. Teaching Points • PF disorders commonly cause heel pain and disability in the general population.• Imaging is often required to confirm diagnosis or reveal concomitant injuries.• Ultrasound and MRI respectively represent the first- and second-line modalities for diagnosis.• Indirect findings of PF disease can be ruled out on plain radiography.

Resonant multiphoton ionization of caesium atoms by ultra-short laser pulses at 1.06 μm

International Nuclear Information System (INIS)

Lompre, L.A.; Mainfray, G.; Manus, C.; Thebault, J.

1978-01-01

This paper reports the four-photon ionization of caesium atoms when the laser frequency is tuned through the resonant three-photon transition 6S → 6F. This experiment was performed by using a tunable-wavelength bandwidth-limited subnanosecond laser pulse at 1.06 μm, in the 10 8 -10 9 W.cm -2 laser intensity range. Pulse widths of 1.5 ns, 50 ps, and 15 ps were used. The resonant character of the multiphoton ionization process was observed, even with the shortest pulse of 15 ps. Nevertheless the influence of a temporal effect is demonstrated according to theoretical predictions. The resonance shift ΔE of the 6S → 6F transition energy was found to be linear with the laser intensity I within the range 10 8 -10 9 W.cm -2 . ΔE = αI, with α = 2 cm -1 /GW.cm -2 . This results confirms previous measurements performed with single-mode 35 ns laser pulses and is in very good agreement with calculated resonance shifts

Anal carcinomas: the role of endoanal ultrasound and magnetic resonance imaging in staging, response evaluation and follow-up

Energy Technology Data Exchange (ETDEWEB)

Parikh, Jyoti; Shaw, Aidan; Griffin, Nyree [Guys and St. Thomas' Hospital, Department of Radiology, London (United Kingdom); Grant, Lee A. [Royal Marsden Hospital, Department of Radiology, London (United Kingdom); Schizas, Alexis M.P.; Datta, Vivek; Williams, Andrew B. [Guys and St. Thomas' Hospital, Department of General Surgery, London (United Kingdom)

2011-04-15

Anal carcinoma is an important but rare condition, managed in specialist centres. Both endoanal ultrasound and magnetic resonance imaging (MRI) can be used in the locoregional staging and follow-up of patients with anal cancer, and both may assist in treatment planning and prognosis. Recent guidelines published by the European Society for Medical Oncology have recommended MRI as the technique of choice for assessment of locoregional disease. This paper describes the techniques for both endoanal ultrasound and MRI, and compares the relative merits and disadvantages of each in the local assessment of anal carcinoma. (orig.)

All-optical extravascular laser-ultrasound and photoacoustic imaging of calcified atherosclerotic plaque in excised carotid artery

Directory of Open Access Journals (Sweden)

Jami L. Johnson

2018-03-01

Full Text Available Photoacoustic (PA imaging may be advantageous as a safe, non-invasive imaging modality to image the carotid artery. However, calcification that accompanies atherosclerotic plaque is difficult to detect with PA due to the non-distinct optical absorption spectrum of hydroxyapatite. We propose reflection-mode all-optical laser-ultrasound (LUS imaging to obtain high-resolution, non-contact, non-ionizing images of the carotid artery wall and calcification. All-optical LUS allows for flexible acquisition geometry and user-dependent data acquisition for high repeatability. We apply all-optical techniques to image an excised human carotid artery. Internal layers of the artery wall, enlargement of the vessel, and calcification are observed with higher resolution and reduced artifacts with nonconfocal LUS compared to confocal LUS. Validation with histology and X-ray computed tomography (CT demonstrates the potential for LUS as a method for non-invasive imaging in the carotid artery. Keywords: Atherosclerosis, Photoacoustic imaging, Laser-ultrasound, Calcification, Reverse-time migration

A MEMS coupled resonator for frequency filtering in air

KAUST Repository

Ilyas, Saad; Jaber, Nizar; Younis, Mohammad I.

2018-01-01

We present design, fabrication, and characterization of a mechanically coupled MEMS H resonator capable of performing simultaneous mechanical amplification and filtering in air. The device comprises of two doubly clamped polyimide microbeams joined

Resonantly enhanced collisional ionization measurements of radionuclides

International Nuclear Information System (INIS)

Whitaker, T.J.; Bushaw, B.A.; Gerke, G.K.

1986-01-01

The authors developed a new laser technique to analyze for radionuclides at extremely low levels. The technique, called resonantly enhanced collisional ionization (RECI), uses two nitrogen-laser pumped dye lasers to excite the target isotope to a high-energy Rydberg state. Atoms in these Rydberg states (within a few hundred wavenumbers in energy from the ionization threshold) efficiently ionize upon colliding with an inert gas and the ions can be detected by conventional means. The principal advantage of resonantly-enhanced collisional ionization is the extreme sensitivity coupled with its relative simplicity and low cost. Actinides typically have an ionization potential of about 6eV (uranium I.P. = 6.2 eV, plutonium I.P. = 5.7 eV). Two-step laser excitation to a state just below threshold requires wavelengths in the blue region of the visible spectrum. They showed that when both steps in the excitation process are resonant steps, relatively low-power lasers can populate the Rydberg state with almost unit efficiency. This is because the resonant excitations have much larger cross-sections than do photoionization processes. They also demonstrated that a few torr of a buffer gas will cause most of the excited-state atoms to be ionized

Resonant exciton-phonon coupling in ZnO nanorods at room temperature

Directory of Open Access Journals (Sweden)

Soumee Chakraborty

2011-09-01

Full Text Available Vibronic and optoelectronic properties, along with detailed studies of exciton-phonon coupling at room temperature (RT for random and aligned ZnO nanorods are reported. Excitation energy dependent Raman studies are performed for detailed analysis of multi-phonon processes in the nanorods. We report here the origin of coupling between free exciton and its associated phonon replicas, including its higher order modes, in the photoluminescence spectra at RT. Resonance of excitonic electron and resonating first order zone center LO phonon, invoked strongly by Frolich interaction, are made responsible for the observed phenomenon.

Anticipated chaos in a nonsymmetric coupled external-cavity-laser system

International Nuclear Information System (INIS)

Rees, Paul; Spencer, Paul S.; Pierce, Iestyn; Sivaprakasam, S.; Shore, K. Alan

2003-01-01

We explain how the anticipation of chaos in a coupled external cavity laser system described by Sivaprakasam, Shahverdiev, Spencer, and Shore [Phys. Rev. Lett. 87, 154101 (2001)] is obtained. We show that the external cavity induces the required symmetry breaking necessary for the existence of a time delay between the synchronized output of the two laser diodes. The inclusion of a detuning between the two lasers causes one laser to anticipate the chaotic dynamics of the other

Three-Rod Resonator for Krypton Lamp Pumped 1.8 kW Continuous-Wave Nd:YAG Laser

Institute of Scientific and Technical Information of China (English)

LI Qiang; FANG Ming-Xing; WANG Zhi-Yong; YU Zhen-Sheng; LEI Hong; GUO Jiang; LI Gang; ZUO Tie-Chuan

2004-01-01

@@ A three-rod series resonator cw Nd:YAG laser suitable for the industrial applications is presented. The symmetrical resonator laser has been developed and is rated at 1820-W output power with beam parameter product 24 mm.mrad. By utilizing the symmetrical resonator design, the characteristic of beam with multi-rod is not obviously decreased compared with that of a single one. The system total electro-optics efficiency of lamp pumped YAG crystal is as high as 4.0%. The main factors, which affect output power and beam quality of high power solid-state laser module, are theoretically analysed.

Femtosecond Laser Structuring in Optical Fiber and Transparent Films

Directory of Open Access Journals (Sweden)

Herman Peter R.

2013-11-01

Full Text Available Femtosecond laser processing is optimized for writing optical circuits, optical resonators, and microfluidic devices inside the cladding of single-mode optical fiber that couple efficiently with the fiber core waveguide. The laser processes open new directions towards Labon-a-Fiber.

Magnetic resonance imaging, ultrasound and real-time ultrasound elastography of the thigh muscles in congenital muscle dystrophy

Energy Technology Data Exchange (ETDEWEB)

Drakonaki, Eleni E. [University of Crete, Radiology Department, Heraklion (Greece); Allen, Gina M. [Green Templeton College, Oxford (United Kingdom)

2010-04-15

Congenital muscle dystrophy includes a range of genetic disorders characterized by muscle weakness and contractures. We report the magnetic resonance (MR), ultrasound (US) and real-time sonoelastography (RTE) imaging findings of the thigh muscles of a 15-year-old boy with Bethlem myopathy diagnosed with clinical, electromyographic and histopathological criteria. Ultrasound and MR showed hyperechoic appearance and high signal intensity on T1- and T2-weighted sequences respectively at the periphery of the vastus lateralis and the long head of the biceps femoris muscles, and at a central area within the rectus femoris muscles. RTE was employed to examine the elastic properties of the muscle. The elastograms were presented as colour-coded maps superimposed on the B-mode images and revealed that the elastographic pattern correlated with the MR and US pattern of involvement. The abnormal muscle areas were stiffer (blue) than the normal-appearing areas (green), a finding that probably correlates with the presence of dystrophic collagen at the affected areas. This report suggests that RTE could be used as an additional imaging tool to evaluate the pattern of muscle changes in congenital myopathy. Further studies are needed to investigate the specificity and clinical value of RTE in the diagnosis and monitoring of neuromuscular disease. (orig.)

Magnetic resonance imaging, ultrasound and real-time ultrasound elastography of the thigh muscles in congenital muscle dystrophy

International Nuclear Information System (INIS)

Drakonaki, Eleni E.; Allen, Gina M.

2010-01-01

Congenital muscle dystrophy includes a range of genetic disorders characterized by muscle weakness and contractures. We report the magnetic resonance (MR), ultrasound (US) and real-time sonoelastography (RTE) imaging findings of the thigh muscles of a 15-year-old boy with Bethlem myopathy diagnosed with clinical, electromyographic and histopathological criteria. Ultrasound and MR showed hyperechoic appearance and high signal intensity on T1- and T2-weighted sequences respectively at the periphery of the vastus lateralis and the long head of the biceps femoris muscles, and at a central area within the rectus femoris muscles. RTE was employed to examine the elastic properties of the muscle. The elastograms were presented as colour-coded maps superimposed on the B-mode images and revealed that the elastographic pattern correlated with the MR and US pattern of involvement. The abnormal muscle areas were stiffer (blue) than the normal-appearing areas (green), a finding that probably correlates with the presence of dystrophic collagen at the affected areas. This report suggests that RTE could be used as an additional imaging tool to evaluate the pattern of muscle changes in congenital myopathy. Further studies are needed to investigate the specificity and clinical value of RTE in the diagnosis and monitoring of neuromuscular disease. (orig.)

New possibilities for using laser polarimetry technology to study electron paramagnetic resonance

Energy Technology Data Exchange (ETDEWEB)

Aleksandrov, E V; Zapasskii, V S

1982-01-01

Optical methods of recording electron paramagnetic resonance which arose in the early 50's as applied to the problem of recording the magnetic resonance of excited atoms is at the present time widely used in studying the electron paramagnetic resonance of the ground and excited states of free atoms and paramagnetic centers in condensed media. At the present time attention is devoted to the additional possibilities of optical methods of electron paramagnetic resonance which are realized using laser sources.

Bunching and phase focusing of laser generated proton beams

Energy Technology Data Exchange (ETDEWEB)

Schumacher, Dennis; Hofmann, Ingo; Blazevic, Abel; Deppert, Oliver [GSI Helmholtzzentrum fuer Schwerionenforschung (Germany); Busold, Simon; Roth, Markus; Boine-Frankenheim, Oliver [TU Darmstadt (Germany); Brabetz, Christian [Universitaet Frankfurt, Frankfurt am Main (Germany); Zielbauer, Bernhard [HI Jena (Germany); Collaboration: LIGHT-Collaboration

2013-07-01

Laser accelerated proton beams can reach very high intensities and very low emittances. Therefore they are suitable as ion sources for many applications. One is the coupling into common ion accelerator structures to replace pre accelerators that are used so far. The LIGHT (Laser Ion Generation, Handling and Transport) collaboration has been founded to develop ion optics and targets and optimize laser parameter to make this coupling most efficient. In a first step a short pulse beam line for the PHELIX-laser at GSI to the experiment site Z6 has been build in order to laser accelerate protons here. In a second step a pulsed solenoid has been established to collimate the divergent ion beam. In a third step this collimated beam will be coupled into a bunching unit, which consists of a spiral resonator with three gaps which leads to an overall acceleration voltage of 1 MV. With this cavity it is not only possible to avoid the broadening of the pulse, but also to phase focus it. This talk presents also the progress towards the operation of the spiral resonator as buncher for a laser accelerated ion beam e.g. simulations, tests and performance data and shows the next steps of the beam shaping efforts.

Mode structure of delay-coupled semiconductor lasers: influence of the pump current

International Nuclear Information System (INIS)

Erzgraeber, Hartmut; Krauskopf, Bernd; Lenstra, Daan

2005-01-01

We consider two identical, mutually delay-coupled semiconductor lasers and show that their compound laser modes (CLMs)-the basic continuous wave solutions-depend rather sensitively on the pump current of the lasers. Specifically, we show with figures and accompanying animations how the underlying CLM structure and the associated locking region, where both lasers operate stably with the same frequency, change as a function of the pump current. Our results provide a natural transition between rather different CLM structures that have been reported in the literature. Moreover, we demonstrate how the locking region as well as the different types of instabilities at its boundary depend on the pump current. This is of fundamental interest for the dynamics of coupled lasers and their possible application

A pulsated weak-resonant-cavity laser diode with transient wavelength scanning and tracking for injection-locked RZ transmission.

Science.gov (United States)

Lin, Gong-Ru; Chi, Yu-Chieh; Liao, Yu-Sheng; Kuo, Hao-Chung; Liao, Zhi-Wang; Wang, Hai-Lin; Lin, Gong-Cheng

2012-06-18

By spectrally slicing a single longitudinal-mode from a master weak-resonant-cavity Fabry-Perot laser diode with transient wavelength scanning and tracking functions, the broadened self-injection-locking of a slave weak-resonant-cavity Fabry-Perot laser diode is demonstrated to achieve bi-directional transmission in a 200-GHz array-waveguide-grating channelized dense-wavelength-division-multiplexing passive optical network system. Both the down- and up-stream slave weak-resonant-cavity Fabry-Perot laser diodes are non-return-to-zero modulated below threshold and coherently injection-locked to deliver the pulsed carrier for 25-km bi-directional 2.5 Gbits/s return-to-zero transmission. The master weak-resonant-cavity Fabry-Perot laser diode is gain-switched at near threshold condition and delivers an optical coherent pulse-train with its mode linewidth broadened from 0.2 to 0.8 nm by transient wavelength scanning, which facilitates the broadband injection-locking of the slave weak-resonant-cavity Fabry-Perot laser diodes with a threshold current reducing by 10 mA. Such a transient wavelength scanning induced spectral broadening greatly releases the limitation on wavelength injection-locking range required for the slave weak-resonant-cavity Fabry-Perot laser diode. The theoretical modeling and numerical simulation on the wavelength scanning and tracking effects of the master and slave weak-resonant-cavity Fabry-Perot laser diodes are performed. The receiving power sensitivity for back-to-back transmission at bit-error-rate transmission is less than 2 dB for all 16 channels.

Comparative study of the effects of the Ga-As (904 nm, 150 mW) laser and the pulsed ultrasound of 1 MHz in inflammation of tibialis muscle of Wistar rats

Energy Technology Data Exchange (ETDEWEB)

Pinto, Marcus Vinicius de Mello; Rocha, Lamara Laguardia Valente; Santos, Helio Ricardo dos; Silva, Andre Luis dos Santos; Barbosa, Luis Guilherme; Reis, Joao Batista Alves dos [Centro Universitario de Caratinga, MG (Brazil)]. E-mail; orofacial_1@hotmail.com; Costa, Daniel Almeida da [Faculdade de Minas, Belo Horizonte, MG (Brazil); Bernardo-Filho, Mario [Universidade do Estado do Rio de Janeiro (UERJ), RJ (Brazil). Inst. de Biologia Roberto Alcantara Gomes. Dept. de Biofisica e Biometria

2008-12-15

This paper aims to compare the therapeutic effect of the laser As-Ga of 904 nm and pulsed Ultrasound of 1 MHz applied in striated skeletal muscle of inflamed rats. The animals received an intramuscular injection of bupivacaine hydrochloride in tibialis muscle in order to induce the inflammatory process, and after 24 hours, the time was considered 0 for the initiation of therapy, using a laser and ultrasound. Samples collected the muscles of the animals were stained with Hematoxylin-Eosin and histological sections of the groups used for the analysis of the muscle tissue in relation to reducing the inflammatory process, comparing the results of the two therapies used. In this study it is suggested that both treatment with laser as with ultrasound can act as anti-inflammatory. However, the laser seems to have anti-inflammatory effect for all periods observed, while the ultrasound was only able to induce declining inflammatory response to seven days. (author)

Comparative study of the effects of the Ga-As (904 nm, 150 mW) laser and the pulsed ultrasound of 1 MHz in inflammation of tibialis muscle of Wistar rats

International Nuclear Information System (INIS)

Pinto, Marcus Vinicius de Mello; Rocha, Lamara Laguardia Valente; Santos, Helio Ricardo dos; Silva, Andre Luis dos Santos; Barbosa, Luis Guilherme; Reis, Joao Batista Alves dos . E-mail; Costa, Daniel Almeida da; Bernardo-Filho, Mario

2008-01-01

This paper aims to compare the therapeutic effect of the laser As-Ga of 904 nm and pulsed Ultrasound of 1 MHz applied in striated skeletal muscle of inflamed rats. The animals received an intramuscular injection of bupivacaine hydrochloride in tibialis muscle in order to induce the inflammatory process, and after 24 hours, the time was considered 0 for the initiation of therapy, using a laser and ultrasound. Samples collected the muscles of the animals were stained with Hematoxylin-Eosin and histological sections of the groups used for the analysis of the muscle tissue in relation to reducing the inflammatory process, comparing the results of the two therapies used. In this study it is suggested that both treatment with laser as with ultrasound can act as anti-inflammatory. However, the laser seems to have anti-inflammatory effect for all periods observed, while the ultrasound was only able to induce declining inflammatory response to seven days. (author)

Dynamics of chaotic oscillations in mutually coupled microchip lasers

CERN Document Server

Uchida, A; Kinugawa, S; Yoshimori, S

2003-01-01

We have numerically and experimentally investigated the dynamics of mutually coupled microchip lasers. Chaotic oscillations are observed in the vicinity of the boundary of the injection-locking range when the coupling strength and the difference of the optical frequencies are varied. Synchronization of chaos is always achieved under the condition to generate chaos.

Induced high-order resonance linewidth shrinking with multiple coupled resonators in silicon-organic hybrid slotted two-dimensional photonic crystals for reduced optical switching power in bistable devices

Science.gov (United States)

Hoang, Thu Trang; Ngo, Quang Minh; Vu, Dinh Lam; Le, Khai Q.; Nguyen, Truong Khang; Nguyen, Hieu P. T.

2018-01-01

Shrinking the linewidth of resonances induced by multiple coupled resonators is comprehensively analyzed using the coupled-mode theory (CMT) in time. Two types of coupled resonators under investigation are coupled resonator optical waveguides (CROWs) and side-coupled resonators with waveguide (SCREW). We examine the main parameters influencing on the spectral response such as the number of resonators (n) and the phase shift (φ) between two adjacent resonators. For the CROWs geometry consisting of n coupled resonators, we observe the quality (Q) factor of the right- and left-most resonant lineshapes increases n times larger than that of a single resonator. For the SCREW geometry, relying on the phase shift, sharp, and asymmetric resonant lineshape of the high Q factor a narrow linewidth of the spectral response could be achieved. We employ the finite-difference time-domain (FDTD) method to design and simulate two proposed resonators for practical applications. The proposed coupled resonators in silicon-on-insulator (SOI) slotted two-dimensional (2-D) photonic crystals (PhCs) filled and covered with a low refractive index organic material. Slotted PhC waveguides and cavities are designed to enhance the electromagnetic intensity and to confine the light into small cross-sectional area with low refractive index so that efficient optical devices could be achieved. A good agreement between the theoretical CMT analysis and the FDTD simulation is shown as an evidence for our accurate investigation. All-optical switches based on the CROWs in the SOI slotted 2-D PhC waveguide that are filled and covered by a nonlinear organic cladding to overcome the limitations of its well-known intrinsic properties are also presented. From the calculations, we introduce a dependency of the normalized linewidth of the right-most resonance and its switching power of the all-optical switches on number of resonator, n. This result might provide a guideline for all-optical signal processing on

Study on frequency characteristics of wireless power transmission system based on magnetic coupling resonance

Science.gov (United States)

Liang, L. H.; Liu, Z. Z.; Hou, Y. J.; Zeng, H.; Yue, Z. K.; Cui, S.

2017-11-01

In order to study the frequency characteristics of the wireless energy transmission system based on the magnetic coupling resonance, a circuit model based on the magnetic coupling resonant wireless energy transmission system is established. The influence of the load on the frequency characteristics of the wireless power transmission system is analysed. The circuit coupling theory is used to derive the minimum load required to suppress frequency splitting. Simulation and experimental results verify that when the load size is lower than a certain value, the system will appear frequency splitting, increasing the load size can effectively suppress the frequency splitting phenomenon. The power regulation scheme of the wireless charging system based on magnetic coupling resonance is given. This study provides a theoretical basis for load selection and power regulation of wireless power transmission systems.

Improving the laser brightness of a commercial laser system

Science.gov (United States)

Naidoo, Darryl; Litvin, Igor; Forbes, Andrew

2016-02-01

We investigate the selection of a flat-top beam and a Gaussian beam inside a laser cavity on opposing mirrors. The concept is tested external to the laser cavity in a single pass and double pass regime where the latter mimics a single round trip in the laser. We implement this intra-cavity selection through the use of two 16 level diffractive optical elements. We consider a solid-state diode side-pumped laser resonator in a typical commercial laser configuration that consists of two planar mirrors where the DOEs are positioned at the mirrors. We out couple the Gaussian and flat-top distributions and we show that we improve the brightness of the laser with active mode control. We also demonstrate that the quality of the beam transformations determine the brightness improvement.

Microwave-to-optical frequency conversion using a cesium atom coupled to a superconducting resonator

Science.gov (United States)

Gard, Bryan T.; Jacobs, Kurt; McDermott, R.; Saffman, M.

2017-07-01

A candidate for converting quantum information from microwave to optical frequencies is the use of a single atom that interacts with a superconducting microwave resonator on one hand and an optical cavity on the other. The large electric dipole moments and microwave transition frequencies possessed by Rydberg states allow them to couple strongly to superconducting devices. Lasers can then be used to connect a Rydberg transition to an optical transition to realize the conversion. Since the fundamental source of noise in this process is spontaneous emission from the atomic levels, the resulting control problem involves choosing the pulse shapes of the driving lasers so as to maximize the transfer rate while minimizing this loss. Here we consider the concrete example of a cesium atom, along with two specific choices for the levels to be used in the conversion cycle. Under the assumption that spontaneous emission is the only significant source of errors, we use numerical optimization to determine the likely rates for reliable quantum communication that could be achieved with this device. These rates are on the order of a few megaqubits per second.

Uterus and ovaries in girls and young women with Turner syndrome evaluated by ultrasound and magnetic resonance imaging

DEFF Research Database (Denmark)

Cleemann, Line; Holm, Kirsten; Fallentin, Eva

2011-01-01

Objective To determine uterine and ovarian size in Turner syndrome (TS) and to compare uterine and ovarian size evaluated by transabdominal ultrasound (US) and magnetic resonance imaging (MRI) in girls with TS and two groups of controls. Design A cross-sectional study. Patients Forty-one girls...

Modeling and simulation of two-step resonance ionization processes using CW and pulsed lasers

CERN Document Server

de Groote, Ruben; Flanagan, Kieran

This thesis derives and discusses equations that describe the evolution of atomic systems subjected to two monochromatic and coherent radiation fields and treats both continuous and temporally pulsed irradiation. This theoretical description is de- veloped mainly to understand the influence of the photon field intensities on experimental ionization spectra. The primary ap- plication of this theoretical framework is on methods that rely on resonant laser excitation and non-resonant laser ionization to extract information on the hyperfine structure of atomic systems. In particular, qualitative and quantitative discussions on the laser-related changes in hyperfine splitting extracted from ion- ization spectra are presented. Also, a method for increasing the resolution of resonance ionization techniques (potentially up un- til the natural linewidth of the electronic transitions) is discussed and theoretically justified. Both topics are illustrated with exper- imental data.

Coupled-resonator optical waveguides: Q-factor and disorder influence

DEFF Research Database (Denmark)

Grgic, Jure; Campaioli, Enrico; Raza, Søren

2011-01-01

Coupled resonator optical waveguides (CROW) can significantly reduce light propagation pulse velocity due to pronounced dispersion properties. A number of interesting applications have been proposed to benefit from such slow-light propagation. Unfortunately, the inevitable presence of disorder...

Quantum averaging and resonances: two-level atom in a one-mode classical laser field

Directory of Open Access Journals (Sweden)

M. Amniat-Talab

2007-06-01

Full Text Available   We use a nonperturbative method based on quantum averaging and an adapted from of resonant transformations to treat the resonances of the Hamiltonian of a two-level atom interacting with a one-mode classical field in Floquet formalism. We illustrate this method by extraction of effective Hamiltonians of the system in two regimes of weak and strong coupling. The results obtained in the strong-coupling regime, are valid in the whole range of the coupling constant for the one-photon zero-field resonance.

Time-dependent resonant tunnelling for parallel-coupled double quantum dots

International Nuclear Information System (INIS)

Dong Bing; Djuric, Ivana; Cui, H L; Lei, X L

2004-01-01

We derive the quantum rate equations for an Aharonov-Bohm interferometer with two vertically coupled quantum dots embedded in each of two arms by means of the nonequilibrium Green function in the sequential tunnelling regime. Based on these equations, we investigate time-dependent resonant tunnelling under a small amplitude irradiation and find that the resonant photon-assisted tunnelling peaks in photocurrent demonstrate a combination behaviour of Fano and Lorentzian resonances due to the interference effect between the two pathways in this parallel configuration, which is controllable by threading the magnetic flux inside this device

Resonant enhanced parallel-T topology for weak coupling wireless power transfer pickup applications

Directory of Open Access Journals (Sweden)

Yao Guo

2015-07-01

Full Text Available For the wireless power transfer (WPT system, the transfer performance and the coupling coefficient are contradictory. In this paper, a novel parallel-T resonant topology consists of a traditional parallel circuit and a T-matching network for secondary side is proposed. With this method, a boosted voltage can be output to the load, since this topology has a resonant enhancement effect, and high Q value can be obtained at a low resonant frequency and low coil inductance. This feature makes it more suitable for weak coupling WPT applications. Besides, the proposed topology shows good frequency stability and adaptability to variations of load. Experimental results show that the output voltage gain improves by 757% compared with traditional series circuit, and reaches 85% total efficiency when the coupling coefficient is 0.046.

Resonance tuning due to Coulomb interaction in strong near-field coupled metamaterials

International Nuclear Information System (INIS)

Roy Chowdhury, Dibakar; Xu, Ningning; Zhang, Weili; Singh, Ranjan

2015-01-01

Coulomb's law is one of the most fundamental laws of physics that describes the electrostatic interaction between two like or unlike point charges. Here, we experimentally observe a strong effect of Coulomb interaction in tightly coupled terahertz metamaterials where the split-ring resonator dimers in a unit cell are coupled through their near fields across the capacitive split gaps. Using a simple analytical model, we evaluated the Coulomb parameter that switched its sign from negative to positive values indicating the transition in the nature of Coulomb force from being repulsive to attractive depending upon the near field coupling between the split ring resonators. Apart from showing interesting effects in the strong coupling regime between meta-atoms, Coulomb interaction also allows an additional degree of freedom to achieve frequency tunable dynamic metamaterials

A three-dimensional model for calculating the micro disk laser resonant-modes

International Nuclear Information System (INIS)

Sabetjoo, H.; Bahrampor, A.; Farrahi-Moghaddam, R.

2006-01-01

In this article, a semi-analytical model for theoretical analysis of micro disk lasers is presented. Using this model, the necessary conditions for the existence of loss less and low-loss modes of micro-resonators are obtained. The resonance frequency of the resonant modes and also the attenuation of low-loss modes are calculated. By comparing the results with results of finite difference method, their validity is certified.

Compact HTS bandpass filter employing CPW quarter-wavelength resonators with strongly-coupled open stubs

Energy Technology Data Exchange (ETDEWEB)

Satoh, K; Koizumi, D; Narahashi, S [Research Laboratories, NTT DoCoMo, Inc., 3-5 Hikari-no-oka, Yokosuka, Kanagwa, 239-8536 (Japan)], E-mail: satokei@nttdocomo.co.jp

2008-02-01

This paper presents a novel compact high temperature superconducting (HTS) bandpass filter (BPF) that employs a newly developed miniaturized coplanar-waveguide (CPW) quarter-wavelength resonators with strongly-coupled open stubs. The proposed resonator has a structure in which the open stubs are aligned close to the center conductor of the resonator. This is because strongly-coupled resonators have widely-split resonant frequencies, and the lowest resonant frequency is employed as the fundamental resonant frequency of the resonator in order to achieve miniaturization. The proposed resonator is 1.7 mm or less in length for use in the 5-GHz band, whereas the conventional straight resonator is approximately 6.4 mm long. A four-pole Chebyshev HTS BPF is designed and fabricated using the proposed CPW resonators. The entire length of the proposed four-pole filter is 15 mm. The frequency response of the fabricated filter agrees well with the electromagnetic simulation results. The proposed filter achieves a size reduction of at least 50% compared to previously reported filters without any degradation in the frequency characteristics.

Development of Laser-Polarized Noble Gas Magnetic Resonance Imaging (MRI) Technology

Science.gov (United States)

Walsworth, Ronald L.

2004-01-01

We are developing technology for laser-polarized noble gas nuclear magnetic resonance (NMR), with the aim of enabling it as a novel biomedical imaging tool for ground-based and eventually space-based application. This emerging multidisciplinary technology enables high-resolution gas-space magnetic resonance imaging (MRI)-e.g., of lung ventilation, perfusion, and gas-exchange. In addition, laser-polarized noble gases (3He and 1BXe) do not require a large magnetic field for sensitive NMR detection, opening the door to practical MRI with novel, open-access magnet designs at very low magnetic fields (and hence in confined spaces). We are pursuing two specific aims in this technology development program. The first aim is to develop an open-access, low-field (less than 0.01 T) instrument for MRI studies of human gas inhalation as a function of subject orientation, and the second aim is to develop functional imaging of the lung using laser-polarized He-3 and Xe-129.

Comparison of fiber lasers based on distributed side-coupled cladding-pumped fibers and double-cladding fibers.

Science.gov (United States)

Huang, Zhihe; Cao, Jianqiu; Guo, Shaofeng; Chen, Jinbao; Xu, Xiaojun

2014-04-01

We compare both analytically and numerically the distributed side-coupled cladding-pumped (DSCCP) fiber lasers and double cladding fiber (DCF) lasers. We show that, through optimization of the coupling and absorbing coefficients, the optical-to-optical efficiency of DSCCP fiber lasers can be made as high as that of DCF lasers. At the same time, DSCCP fiber lasers are better than the DCF lasers in terms of thermal management.

Combined Conformal Strongly-Coupled Magnetic Resonance for Efficient Wireless Power Transfer

Directory of Open Access Journals (Sweden)

Matjaz Rozman

2017-04-01

Full Text Available This paper proposes a hybrid circuit between a conformal strongly-coupled magnetic resonance (CSCMR and a strongly-coupled magnetic resonance (SCMR, for better wireless power transmission (WPT. This combination promises to enhance the flexibility of the proposed four-loop WPT system. The maximum efficiency at various distances is achieved by combining coupling-matching between the source and transmitting coils along with the coupling factor between the transmitting and receiving coils. Furthermore, the distance between transmitting and receiving coils is investigated along with the distance relationship between the source loop and transmission coil, in order to achieve the maximum efficiency of the proposed hybrid WPT system. The results indicate that the proposed approach can be effectively employed at distances comparatively smaller than the maximum distance without frequency matching. The achievable efficiency can be as high as 84% for the whole working range of the transmitter. In addition, the proposed hybrid system allows more spatial freedom compared to existing chargers.

[Diagnosis. Radiological study. Ultrasound, computed tomography and magnetic resonance imaging].

Science.gov (United States)

Gallo Vallejo, Francisco Javier; Giner Ruiz, Vicente

2014-01-01

Because of its low cost, availability in primary care and ease of interpretation, simple X-ray should be the first-line imaging technique used by family physicians for the diagnosis and/or follow-up of patients with osteoarthritis. Nevertheless, this technique should only be used if there are sound indications and if the results will influence decision-making. Despite the increase of indications in patients with rheumatological disease, the role of ultrasound in patients with osteoarthritis continues to be limited. Computed tomography (CT) is of some -although limited- use in osteoarthritis, especially in the study of complex joints (such as the sacroiliac joint and facet joints). Magnetic resonance imaging (MRI) has represented a major advance in the evaluation of joint cartilage and subchondral bone in patients with osteoarthritis but, because of its high cost and diagnostic-prognostic yield, this technique should only be used in highly selected patients. The indications for ultrasound, CT and MRI in patients with osteoarthritis continue to be limited in primary care and often coincide with situations in which the patient may require hospital referral. Patient safety should be bourne in mind. Patients should be protected from excessive ionizing radiation due to unnecessary repeat X-rays or inadequate views or to requests for tests such as CT, when not indicated. Copyright © 2014 Elsevier España, S.L. All rights reserved.

Electromagnetically induced transparency with large delay-bandwidth product induced by magnetic resonance near field coupling to electric resonance

Energy Technology Data Exchange (ETDEWEB)

Li, Hai-ming; Liu, Shao-bin, E-mail: lsb@nuaa.edu.cn; Liu, Si-yuan; Zhang, Hai-feng; Bian, Bo-rui; Kong, Xiang-kun [Key Laboratory of Radar Imaging and Microwave Photonics, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Wang, Shen-yun [Research Center of Applied Electromagnetics, Nanjing University of Information Science and Technology, Nanjing 210044 (China)

2015-03-16

In this paper, we numerically and experimentally demonstrate electromagnetically induced transparency (EIT)-like spectral response with magnetic resonance near field coupling to electric resonance. Six split-ring resonators and a cut wire are chosen as the bright and dark resonator, respectively. An EIT-like transmission peak located between two dips can be observed with incident magnetic field excitation. A large delay bandwidth product (0.39) is obtained, which has potential application in quantum optics and communications. The experimental results are in good agreement with simulated results.

Resonant Laser Manipulation of an Atomic Beam

Science.gov (United States)

2010-07-01

Technical Paper 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Resonant Laser Manipulation of an Atomic Beam...steering and collimating flows with higher densities and energies than current common practice . One impediment to this extension is the development of...where Δεg is the ground state Stark shift, Ω is the Rabi frequency (related to intensity), Isat is the saturation intensity of the transition, and I(r

Resonant gravimetric immunosensing based on capacitive micromachined ultrasound transducers

KAUST Repository

Viržonis, Darius

2014-04-08

High-frequency (40 MHz) and low-frequency (7 MHz) capacitive micromachined ultrasound transducers (CMUT) were fabricated and tested for use in gravimetric detection of biomolecules. The low-frequency CMUT sensors have a gold-coated surface, while the high-frequency sensors have a silicon nitride surface. Both surfaces were functionalized with bovine leukemia virus antigen gp51 acting as the antigen. On addition of an a specific antibody labeled with horseradish peroxidase (HRP), the antigen/antibody complex is formed on the surface and quantified by HRP-catalyzed oxidation of tetramethylbenzidine. It has been found that a considerably smaller quantity of immuno complex is formed on the high frequency sensor surface. In parallel, the loading of the surface of the CMUT was determined via resonance frequency and electromechanical resistance readings. Following the formation of the immuno complexes, the resonance frequencies of the low-frequency and high-frequency sensors decrease by up to 420 and 440 kHz, respectively. Finite element analysis reveals that the loading of the (gold-coated) low frequency sensors is several times larger than that on high frequency sensors. The formation of the protein film with pronounced elasticity and stress on the gold surface case is discussed. We also discuss the adoption of this method for the detection of DNA using a hybridization assay following polymerase chain reaction.

Anisotropy in semipolar InGaN laser diodes: Consequences for resonator design and facet formation

Energy Technology Data Exchange (ETDEWEB)

Rass, Jens; Vogt, Patrick [Technische Universitaet Berlin (Germany). Institute of Solid State Physics; Wernicke, Tim; John, Wilfred; Einfeldt, Sven; Weyers, Markus [Ferdinand-Braun-Institut fuer Hoechstfrequenztechnik, Berlin (Germany); Kneissl, Michael [Technische Universitaet Berlin (Germany). Institute of Solid State Physics; Ferdinand-Braun-Institut fuer Hoechstfrequenztechnik, Berlin (Germany)

2010-07-01

For InAlGaN-based light emitting devices on nonpolar and semipolar substrate orientations the polarization fields can be reduced. Birefringence and gain anisotropy influence the optical modes of semipolar separate confinement hetero structures. We have investigated the threshold for amplified spontaneous emission and the optical polarization state of the eigenmodes for laser resonators with different orientations on various semipolar and nonpolar substrates. We found that semipolar resonators along the projection of the c-axis onto the surface have a lower threshold and the light is TE-polarized. Nonpolar resonators perpendicular to the c-axis on the other hand have elevated thresholds and hence a lower gain as well as a tilted linear optical polarization with the electric field nearly parallel to the c-axis of the crystal. In order to obtain devices with low threshold and maximum performance, laser resonators on semipolar substrates have to be oriented along the semipolar orientation, posing a challenge for the fabrication of laser facets. Technologies such as laser assisted cleaving, chemical dry etching and wet chemical post processing are presented and their suitability for the generation of smooth vertical facets is discussed.

Laser Resonators and Beam Propagation Fundamentals, Advanced Concepts and Applications

CERN Document Server

Hodgson, Norman

2005-01-01

Optical Resonators provides a detailed discussion of the properties of optical resonators for lasers from basic theory to recent research. In addition to describing the fundamental theories of resonators such as geometrical optics, diffraction, and polarisation the characteristics of all important resonator schemes and their calculation are presented. Experimental examples, practical problems and a collection of measurement techniques support the comprehensive treatment of the subject. Optical Resonators is the only book currently available that provides a comprehensive overview of the the subject. Combined with the structure of the text and the autonomous nature of the chapters this work will be as suitable for those new to the field as it will be invaluable to specialists conducting research. This second edition has been enlarged by new sections on Q-switching and resonators with internal phase/amplitude control. In addition, the whole book has been brought up-to-date.

Wavelength-dependent Faraday–Tyndall effect on laser-induced microbubble in gold colloid

International Nuclear Information System (INIS)

Liaw, Jiunn-Woei; Tsai, Shiao-Wen; Lin, Hung-Hsun; Yen, Tzu-Chen; Chen, Bae-Renn

2012-01-01

The cavitation microbubbles in dilute gold colloids of different concentrations (2–10 ppm) induced by a focused nanosecond-pulsed laser beam were measured and characterized at different wavelengths by using the passive and active ultrasound measurements. Three colloids with gold nanoparticles (GNPs) of different sizes (10, 45, and 75 nm) were used for experiment. The results show that the lifespan of the microbubble is reduced as the concentration of GNP increases, particularly at the wavelength of 532 nm, the surface plasmon resonance (SPR) of GNP. In contrast, at the off-resonant wavelength (e.g. 700 nm), the lifespan reduction is relatively small. This wavelength-dependent cavitation is attributed to the Faraday–Tyndall effect, a strong light scattering by GNPs. A slight defocusing of the Gaussian beam in gold colloid was proposed. Hence, the waist of the focused beam increases to reduce the optical breakdown in gold colloid. For simplicity, a linear relation between the incremental waist radius of Gaussian beam and the concentration of GNP was assumed. According to this formulation, the theoretical results are consistent with the experimental ones. In addition, the dynamics of the microbubble in gold colloid measured by the active ultrasound method agree with the Rayleigh–Plesset model. -- Highlights: ► The Faraday–Tyndall effect of gold colloid on laser induced microbubble is studied. ► Faraday–Tyndall effect of gold colloid causes the defocusing of laser beam. ► Lifespan of the microbubble is reduced as the concentration of GNP increases. ► Light scattering of laser beam at the surface plasmon resonance of GNP is the maximum.

[Achilles tendon xanthoma imaging on ultrasound and magnetic resonance imaging].

Science.gov (United States)

Fernandes, Eloy de Ávila; Santos, Eduardo Henrique Sena; Tucunduva, Tatiana Cardoso de Mello; Ferrari, Antonio J L; Fernandes, Artur da Rocha Correa

2015-01-01

The Achilles tendon xanthoma is a rare disease and has a high association with primary hyperlipidemia. An early diagnosis is essential to start treatment and change the disease course. Imaging exams can enhance diagnosis. This study reports the case of a 60-year-old man having painless nodules on his elbows and Achilles tendons without typical gout crisis, followed in the microcrystalline disease clinic of Unifesp for diagnostic workup. Laboratory tests obtained showed dyslipidemia. The ultrasound (US) showed a diffuse Achilles tendon thickening with hypoechoic areas. Magnetic resonance imaging (MRI) showed a diffuse tendon thickening with intermediate signal areas, and a reticulate pattern within. Imaging studies showed relevant aspects to diagnose a xanthoma, thus helping in the differential diagnosis. Copyright © 2014 Elsevier Editora Ltda. All rights reserved.

Magnetic resonance imaging and ultrasound in hepatosplenic schistosomiasis mansoni Ressonância magnética e ultrassonografia na esquistossomose mansoni hepatoesplênica

Directory of Open Access Journals (Sweden)

José Roberto Lambertucci

2004-08-01

Full Text Available We report the findings of abdominal ultrasound and magnetic resonance imaging observed in a patient with advanced schistosomiasis mansoni. A 25-year-old man with hepatosplenic schistosomiasis and variceal bleeding confirmed by upper endoscopy was submitted to abdominal ultrasound and magnetic resonance imaging. During surgery for portal hypertension, a liver biopsy was taken and the diagnosis of Symmers' fibrosis was confirmed. magnetic resonance imaging scans gave more precise information about the gallbladder, periportal thickening and abdominal venous system than did the ultrasound.Relatamos os achados ultrassonográficos e à ressonância magnética intra-abdominais observados em um paciente com esquistossomose mansoni grave. Um homem de 25 anos de idade com esquistossomose hepatoesplênica e sangramento digestivo de varizes esofagianas, com diagnóstico confirmado pela endoscopia, foi submetido à ultrasonografia abdominal e ressonância magnética. Durante a cirurgia de hipertensão porta, um fragmento de fígado foi obtido e o exame histológico confirmou o diagnóstico de fibrose de Symmers. A ressonância magnética forneceu informações mais precisas sobre a vesícula biliar, espessamento periportal e sistema venoso abdominal do que a ultrassonografia.

Characteristics of laser ultrasound interaction with multi-layered dissimilar metals adhesive interface by numerical simulation

Energy Technology Data Exchange (ETDEWEB)

Zhang, Kuanshuang, E-mail: zkuanshuang@buaa.edu.cn [School of Mechanical Engineering and Automation, BeiHang University, Beijing 100191 (China); Collaborative Innovation Center of Advanced Aero-Engine, Beijing 100191 (China); Zhou, Zhenggan; Zhou, Jianghua; Sun, Guangkai [School of Mechanical Engineering and Automation, BeiHang University, Beijing 100191 (China); Collaborative Innovation Center of Advanced Aero-Engine, Beijing 100191 (China)

2015-10-30

Highlights: • We investigate laser generated ultrasound in multi-layered adhesive structure. • We find the difference of waveforms with different probe points. • Probe points and frequency range influence characterization of the damage interface. • Reflection coefficients of longitudinal waves can quantify the void defect. - Abstract: The characteristics of laser-generated ultrasonic wave interaction with multi-layered dissimilar metals adhesive interface are investigated by finite element method (FEM). The physical model of laser-generated ultrasonic wave in the multi-layered dissimilar metals adhesive structure is built. The surface temperature evolution with different laser power densities is analyzed to obtain the parameters of pulsed laser with thermoelastic regime. The differences of laser ultrasonic waves with different center frequencies measured at the center of laser irradiation would verify the interfacial features of adhesive structures. The optimum frequency range and probe point would be beneficial for the detection of the small void defect. The numerical results indicate that the different frequency range and probe points would evidently influence the identification and quantitative characterization of the small void defect. The research findings would lay a foundation for testing interfacial integrity.

Characteristics of laser ultrasound interaction with multi-layered dissimilar metals adhesive interface by numerical simulation

International Nuclear Information System (INIS)

Zhang, Kuanshuang; Zhou, Zhenggan; Zhou, Jianghua; Sun, Guangkai

2015-01-01

Highlights: • We investigate laser generated ultrasound in multi-layered adhesive structure. • We find the difference of waveforms with different probe points. • Probe points and frequency range influence characterization of the damage interface. • Reflection coefficients of longitudinal waves can quantify the void defect. - Abstract: The characteristics of laser-generated ultrasonic wave interaction with multi-layered dissimilar metals adhesive interface are investigated by finite element method (FEM). The physical model of laser-generated ultrasonic wave in the multi-layered dissimilar metals adhesive structure is built. The surface temperature evolution with different laser power densities is analyzed to obtain the parameters of pulsed laser with thermoelastic regime. The differences of laser ultrasonic waves with different center frequencies measured at the center of laser irradiation would verify the interfacial features of adhesive structures. The optimum frequency range and probe point would be beneficial for the detection of the small void defect. The numerical results indicate that the different frequency range and probe points would evidently influence the identification and quantitative characterization of the small void defect. The research findings would lay a foundation for testing interfacial integrity.

Animal study assessing safety of an acoustic coupling fluid that holds the potential to avoid surgically induced artifacts in 3D ultrasound guided operations

International Nuclear Information System (INIS)

Jakola, Asgeir S; Jørgensen, Arve; Selbekk, Tormod; Michler, Ralf-Peter; Solheim, Ole; Torp, Sverre H; Sagberg, Lisa M; Aadahl, Petter; Unsgård, Geirmund

2014-01-01

Use of ultrasound in brain tumor surgery is common. The difference in attenuation between brain and isotonic saline may cause artifacts that degrade the ultrasound images, potentially affecting resection grades and safety. Our research group has developed an acoustic coupling fluid that attenuates ultrasound energy like the normal brain. We aimed to test in animals if the newly developed acoustic coupling fluid may have harmful effects. Eight rats were included for intraparenchymal injection into the brain, and if no adverse reactions were detected, 6 pigs were to be included with injection of the coupling fluid into the subarachnoid space. Animal behavior, EEG registrations, histopathology and immunohistochemistry were used in assessment. In total, 14 animals were included, 8 rats and 6 pigs. We did not detect any clinical adverse effects, seizure activity on EEG or histopathological signs of tissue damage. The novel acoustic coupling fluid intended for brain tumor surgery appears safe in rats and pigs under the tested circumstances

Identification of threshold prostate specific antigen levels to optimize the detection of clinically significant prostate cancer by magnetic resonance imaging/ultrasound fusion guided biopsy.

Science.gov (United States)

Shakir, Nabeel A; George, Arvin K; Siddiqui, M Minhaj; Rothwax, Jason T; Rais-Bahrami, Soroush; Stamatakis, Lambros; Su, Daniel; Okoro, Chinonyerem; Raskolnikov, Dima; Walton-Diaz, Annerleim; Simon, Richard; Turkbey, Baris; Choyke, Peter L; Merino, Maria J; Wood, Bradford J; Pinto, Peter A

2014-12-01

Prostate specific antigen sensitivity increases with lower threshold values but with a corresponding decrease in specificity. Magnetic resonance imaging/ultrasound targeted biopsy detects prostate cancer more efficiently and of higher grade than standard 12-core transrectal ultrasound biopsy but the optimal population for its use is not well defined. We evaluated the performance of magnetic resonance imaging/ultrasound targeted biopsy vs 12-core biopsy across a prostate specific antigen continuum. We reviewed the records of all patients enrolled in a prospective trial who underwent 12-core transrectal ultrasound and magnetic resonance imaging/ultrasound targeted biopsies from August 2007 through February 2014. Patients were stratified by each of 4 prostate specific antigen cutoffs. The greatest Gleason score using either biopsy method was compared in and across groups as well as across the population prostate specific antigen range. Clinically significant prostate cancer was defined as Gleason 7 (4 + 3) or greater. Univariate and multivariate analyses were performed. A total of 1,003 targeted and 12-core transrectal ultrasound biopsies were performed, of which 564 diagnosed prostate cancer for a 56.2% detection rate. Targeted biopsy led to significantly more upgrading to clinically significant disease compared to 12-core biopsy. This trend increased more with increasing prostate specific antigen, specifically in patients with prostate specific antigen 4 to 10 and greater than 10 ng/ml. Prostate specific antigen 5.2 ng/ml or greater captured 90% of upgrading by targeted biopsy, corresponding to 64% of patients who underwent multiparametric magnetic resonance imaging and subsequent fusion biopsy. Conversely a greater proportion of clinically insignificant disease was detected by 12-core vs targeted biopsy overall. These differences persisted when controlling for potential confounders on multivariate analysis. Prostate cancer upgrading with targeted biopsy increases

Laser pulse propagation and enhanced energy coupling to fast electrons in dense plasma gradients

International Nuclear Information System (INIS)

Gray, R J; Carroll, D C; Yuan, X H; Brenner, C M; Coury, M; Quinn, M N; Tresca, O; McKenna, P; Burza, M; Wahlström, C-G; Lancaster, K L; Neely, D; Lin, X X; Li, Y T

2014-01-01

Laser energy absorption to fast electrons during the interaction of an ultra-intense (10 20 W cm −2 ), picosecond laser pulse with a solid is investigated, experimentally and numerically, as a function of the plasma density scale length at the irradiated surface. It is shown that there is an optimum density gradient for efficient energy coupling to electrons and that this arises due to strong self-focusing and channeling driving energy absorption over an extended length in the preformed plasma. At longer density gradients the laser filaments, resulting in significantly lower overall energy coupling. As the scale length is further increased, a transition to a second laser energy absorption process is observed experimentally via multiple diagnostics. The results demonstrate that it is possible to significantly enhance laser energy absorption and coupling to fast electrons by dynamically controlling the plasma density gradient. (paper)

Dynamics of moving interacting atoms in a laser radiation field and optical size resonances

International Nuclear Information System (INIS)

Gadomskii, O.N.; Glukhov, A.G.

2005-01-01

The forces acting on interacting moving atoms exposed to resonant laser radiation are calculated. It is shown that the forces acting on the atoms include the radiation pressure forces as well as the external and internal bias forces. The dependences of the forces on the atomic spacing, polarization, and laser radiation frequency are given. It is found that the internal bias force associated with the interaction of atomic dipoles via the reemitted field may play an important role in the dynamics of dense atomic ensembles in a light field. It is shown that optical size resonances appear in the system of interacting atoms at frequencies differing substantially from transition frequencies in the spectrum of atoms. It is noted that optical size resonances as well as the Doppler frequency shift in the spectrum of interacting atoms play a significant role in the processes of laser-radiation-controlled motion of the atoms

Scattering resonances in a low-dimensional Rashba-Dresselhaus spin-orbit coupled quantum gas

Science.gov (United States)

Wang, Su-Ju; Blume, D.

2017-04-01

Confinement-induced resonances allow for the tuning of the effective one-dimensional coupling constant. When the scattering state associated with the ground transverse mode is brought into resonance with the bound state attached to the energetically excited transverse modes, the atoms interact through an infinitely strong repulsion. This provides a route to realize the Tonks-Girardeau gas. On the other hand, the realization of synthetic gauge fields in cold atomic systems has attracted a lot of attention. For instance, bound-state formation is found to be significantly modified in the presence of spin-orbit coupling in three dimensions. This motivates us to study ultracold collisions between two Rashba-Dresselhaus spin-orbit coupled atoms in a quasi-one-dimensional geometry. We develop a multi-channel scattering formalism that accounts for the external transverse confinement and the spin-orbit coupling terms. The interplay between these two single-particle terms is shown to give rise to new scattering resonances. In particular, it is analyzed what happens when the scattering energy crosses the various scattering thresholds that arise from the single-particle confinement and the spin-orbit coupling. Support by the NSF is gratefully acknowledged.

High Contrast Coherent Population Trapping Resonances in Cs Vapour Cells with a Simple-Architecture Laser System

International Nuclear Information System (INIS)

Liu, Xiaochi

2013-01-01

This thesis reports the development of a simple-architecture laser system resonant at 895 nm used for the detection of high-contrast coherent population trapping (CPT) resonances in Cs vapor cells. The laser system combines a distributed feedback-diode (DFB) laser, a pigtailed Mach-Zehnder intensity electro-optic modulator (EOM) driven at 4.596 GHz for the generation of optical sidebands frequency-split by 9.192 GHz and a Michelson delay-line system to produce a bi-chromatic optical field that alternates between right and left circular polarization. This polarization pumping scheme, first proposed by Happer's group in Princeton on K atoms, allows to optically pump a maximum number of Cs atoms into the 0-0 magnetic field insensitive clock transition. Advanced noise reduction techniques were implemented in order to stabilize the laser power, the optical carrier suppression at the output of the EOM and the DFB laser frequency. Using this system, we demonstrated the detection of CPT resonances with a contrast of 80% in cm-scale Cs vapor cells. This contrast was measured to be increased until a saturation effect with the laser power at the expense of the CPT line broadening. To circumvent this issue, we proposed with a simple setup Ramsey spectroscopy of CPT resonances in vapor cells to combine high-contrast and narrow line width of the CPT resonances. In this setup, the EOM is used both for optical sidebands generation and light switch to produce Ramsey interaction. Ramsey fringes of 166 Hz line width with a contrast better than 30% were detected with this setup. This laser system will be in a near future devoted to be used for the development of a high-performance CPT-based atomic clock. (author)

Rate equation analysis and non-Hermiticity in coupled semiconductor laser arrays

Science.gov (United States)

Gao, Zihe; Johnson, Matthew T.; Choquette, Kent D.

2018-05-01

Optically coupled semiconductor laser arrays are described by coupled rate equations. The coupled mode equations and carrier densities are included in the analysis, which inherently incorporate the carrier-induced nonlinearities including gain saturation and amplitude-phase coupling. We solve the steady-state coupled rate equations and consider the cavity frequency detuning and the individual laser pump rates as the experimentally controlled variables. We show that the carrier-induced nonlinearities play a critical role in the mode control, and we identify gain contrast induced by cavity frequency detuning as a unique mechanism for mode control. Photon-mediated energy transfer between cavities is also discussed. Parity-time symmetry and exceptional points in this system are studied. Unbroken parity-time symmetry can be achieved by judiciously combining cavity detuning and unequal pump rates, while broken symmetry lies on the boundary of the optical locking region. Exceptional points are identified at the intersection between broken symmetry and unbroken parity-time symmetry.

[Magnetic resonance imaging as a prenatal diagnostic tool supplementary to ultrasound in diagnosing fetal and gestational abnormalities].

Science.gov (United States)

Porat, Shay; Agid, Ronit; Elchalal, Uriel; Ezra, Yossi; Gomori, J Moshe; Nadjari, Michelle

2002-04-01

The use of Magnetic Resonance Imaging (MRI) as a prenatal and gestational imaging modality supplementary to ultrasound has become widespread with the advent of rapid MR sequences in the last few years. These sequences allow acquisition of high-resolution images of the fetus in a single breath-holding period of the mother, with minimal fetal motion artifacts. We describe our experience with this modality in the diagnosis of prenatal and gestational abnormalities. The study population consisted of 39 pregnant women who had a total of 40 MRI examinations from 7/1998 to 7/2000. The indication for all examinations was a suspected fetal or gestational abnormality as suggested by ultrasound scan, laboratory tests or by family history. In 31 cases (77.5%) a correlation was found between the ultrasound findings and the MR imaging, of which in 6 cases (15%) the MRI added new valuable information. In 9 cases (22.5%) the MRI ruled out findings suspected by ultrasound. The prenatal findings were compared with postnatal clinical follow-up, imaging or pathology report in 26 cases (66.6%). In two cases the clinical outcome and postnatal imaging were discordant with the prenatal imaging findings in ultrasound and MRI. Although not proven, MRI is considered safe during pregnancy because it does not use ionizing radiation. It depicts fetal anatomy and pathology well. Also uterine, placental and other maternal structures are well demonstrated. This tool is useful in cases in which there is a suspicion of a malformed fetus or abnormal placenta by an ultrasound examination or in cases in which an ultrasound examination is limited by technical factors. MRI was found to help parents and doctors decide about the fate of a suspected abnormal pregnancy by adding valuable information supplemental to ultrasound examination.

Efficient 525 nm laser generation in single or double resonant cavity

Science.gov (United States)

Liu, Shilong; Han, Zhenhai; Liu, Shikai; Li, Yinhai; Zhou, Zhiyuan; Shi, Baosen

2018-03-01

This paper reports the results of a study into highly efficient sum frequency generation from 792 and 1556 nm wavelength light to 525 nm wavelength light using either a single or double resonant ring cavity based on a periodically poled potassium titanyl phosphate crystal (PPKTP). By optimizing the cavity's parameters, the maximum power achieved for the resultant 525 nm laser was 263 and 373 mW for the single and double resonant cavity, respectively. The corresponding quantum conversion efficiencies were 8 and 77% for converting 1556 nm photons to 525 nm photons with the single and double resonant cavity, respectively. The measured intra-cavity single pass conversion efficiency for both configurations was about 5%. The performances of the sum frequency generation in these two configurations was studied and compared in detail. This work will provide guidelines for optimizing the generation of sum frequency generated laser light for a variety of configurations. The high conversion efficiency achieved in this work will help pave the way for frequency up-conversion of non-classical quantum states, such as the squeezed vacuum and single photon states. The proposed green laser source will be used in our future experiments, which includes a plan to generate two-color entangled photon pairs and achieve the frequency down-conversion of single photons carrying orbital angular momentum.

Detection of the Single-Session Complete Ablation Rate by Contrast-Enhanced Ultrasound during Ultrasound-Guided Laser Ablation for Benign Thyroid Nodules: A Prospective Study

Directory of Open Access Journals (Sweden)

Shuhua Ma

2016-01-01

Full Text Available This study aimed to investigate the single-session complete ablation rate of ultrasound-guided percutaneous laser ablation (LA for benign thyroid nodules. LA was performed in 90 patients with 118 benign thyroid nodules. Contrast-enhanced ultrasound (CEUS was used to evaluate complete nodule ablation one day after ablation. Thyroid nodule volumes, thyroid functions, clinical symptoms and complications were evaluated 1, 3, 6, 12, and 18 months after ablation. Results showed that all benign thyroid nodules successfully underwent LA. The single-session complete ablation rates for nodules with maximum diameters ≤2 cm, 2-3 cm and ≥3 cm were 93.4%, 70.3% and 61.1%, respectively. All nodule volumes significantly decreased than that one day after ablation (P0.05. Three patients had obvious pain during ablation; one (1.1% had recurrent laryngeal nerve injury, but the voice returned to normal within 6 months after treatment. Thus, ultrasound-guided LA can effectively inactivate benign thyroid nodules. LA is a potentially viable minimally invasive treatment that offers good cosmetic effects.

Multistabilities and symmetry-broken one-color and two-color states in closely coupled single-mode lasers.

Science.gov (United States)

Clerkin, Eoin; O'Brien, Stephen; Amann, Andreas

2014-03-01

We theoretically investigate the dynamics of two mutually coupled, identical single-mode semi-conductor lasers. For small separation and large coupling between the lasers, symmetry-broken one-color states are shown to be stable. In this case the light outputs of the lasers have significantly different intensities while at the same time the lasers are locked to a single common frequency. For intermediate coupling we observe stable symmetry-broken two-color states, where both lasers lase simultaneously at two optical frequencies which are separated by up to 150 GHz. Using a five-dimensional model, we identify the bifurcation structure which is responsible for the appearance of symmetric and symmetry-broken one-color and two-color states. Several of these states give rise to multistabilities and therefore allow for the design of all-optical memory elements on the basis of two coupled single-mode lasers. The switching performance of selected designs of optical memory elements is studied numerically.

Detection of Breast Microcalcifications Under Ultrasound Using Power Doppler and Acoustic Resonance Imaging

National Research Council Canada - National Science Library

Weinstein, Susan

2003-01-01

.... Our goal with our current project was to utilize breast sonography coupled with the technique of acoustic resonance to image and evaluate the breast micorcalcifications in patients prior to biopsy...

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

Science.gov (United States)

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.

Graphene Oxide and Gadolinium-Chelate Functionalized Poly(lactic acid) Nanocapsules Encapsulating Perfluorooctylbromide for Ultrasound/Magnetic Resonance Bimodal Imaging Guided Photothermal Ablation of Cancer.

Science.gov (United States)

Li, Zhenglin; Ke, Hengte; Wang, Jinrui; Miao, Zhaohua; Yue, Xiuli

2016-03-01

This paper successfully fabricated a novel multifunctional theranostic agent (PFOB@PLA/GO/Gd-DTPA NCs) by loading perfluorooctylbromide (PFOB) into poly(lactic acid) (PLA) nanocapsules (NCs) followed by surface functionalization with graphene oxide (GO) and gadolinium-chelate (Gd-DTPA). It was found that the resulting nanoagent could serve as a contrast agent simultaneously to enhance ultrasound (US) and magnetic resonance imaging (MRI). Benefiting from the strong absorption in the near infrared (NIR) region, the nanocapsules could efficiently kill cancer cells under NIR laser irradiation. Thus, such a single theranostic agent with the combination of realtime US imaging and high-resolution MR imaging could achieve great therapeutic effectiveness without systemic damage to the body. In addition, the cytotoxicity assay on HUVEC cells revealed a good biocompatibility of PFOB@PLA/GO/Gd-DTPA NCs, showing that the versatile nanocapsule system may hold great potential as an effective nanoplatform for contrast enhanced imaging guided photothermal therapy.

Novel laterally pumped by prism laser configuration for compact solid-state lasers

International Nuclear Information System (INIS)

Dascalu, T; Salamu, G; Sandu, O; Voicu, F; Pavel, N

2013-01-01

We propose a new laser configuration in which the pump radiation is coupled into the laser crystal through a prism. The laser medium is square shaped and the prism is attached on one of its lateral sides, near one of the crystal extremities. The diode-laser fiber end is placed close to the prism hypotenuse, the pump radiation is coupled into the laser crystal through the opposite surface of the prism and propagates into the crystal through total internal reflections. This laser geometry is simple to align and permits the realization of compact diode-pumped laser systems, as well as power scaling. A diode-pumped Nd:YAG laser yielding pulses of 2.1 mJ energy under a pump with pulses of 9.9 mJ is demonstrated. The laser slope efficiency is 0.22. Furthermore, this geometry enables one to obtain passively Q-switched lasers with the saturable absorber crystal placed between the resonator high-reflectivity mirror and the laser crystal. A Nd:YAG laser, passively Q-switched by a Cr 4+ :YAG crystal with initial transmission T 0 = 0.90, delivering laser output with a pulsed energy of 93 μJ, a duration of 26 ns and a pump threshold of 1.9 mJ, is realized in order to prove the concept. (letter)

Enhanced vacuum laser-impulse coupling by volume absorption at infrared wavelengths

Science.gov (United States)

Phipps, C. R., Jr.; Harrison, R. F.; Shimada, T.; York, G. W.; Turner, R. F.

1990-03-01

This paper reports measurements of vacuum laser impulse coupling coefficients as large as 90 dyne/W, obtained with single microsec-duration CO2 laser pulses incident on a volume-absorbing, cellulose-nitrate-based plastic. This result is the largest coupling coefficient yet reported at any wavelength for a simple, planar target in vacuum, and partly results from expenditure of internal chemical energy in this material. Enhanced coupling was also observed in several other target materials that are chemically passive, but absorb light in depth at 10- and 3-micron wavelengths. The physical distinctions are discussed between this important case and that of simple, planar surface absorbers (such as metals) which were studied in the same experimental series, in light of the predictions of a simple theoretical model.

Polariton condensation, superradiance and difference combination parametric resonance in mode-locked laser

Science.gov (United States)

Bagayev, S. N.; Arkhipov, R. M.; Arkhipov, M. V.; Egorov, V. S.; Chekhonin, I. A.; Chekhonin, M. A.

2017-11-01

The generation of the ring mode-locked laser containing resonant absorption medium in the cavity was investigated. It is shown that near the strong resonant absorption lines a condensation of polaritons arises. Intensive radiation looks like as superradiance in a medium without population inversion. We studied theoretically the microscopic mechanism of these phenomena. It was shown that in this system in absorbing medium a strong self-induced difference combination parametric resonance exists. Superradiance on polaritonic modes in the absorbing medium are due to the emergence of light-induced resonant polarization as a result of fast periodic nonadiabatic quantum jumps in the absorber.

Study on electromagnetic characteristics of the magnetic coupling resonant coil for the wireless power transmission system.

Science.gov (United States)

Wang, Zhongxian; Liu, Yiping; Wei, Yonggeng; Song, Yilin

2018-01-01

The resonant coil design is taken as the core technology in the magnetic coupling resonant wireless power transmission system, which achieves energy transmission by the coupling of the resonant coil. This paper studies the effect of the resonant coil on energy transmission and the efficiency of the system. Combining a two-coil with a three-coil system, the optimum design method for the resonant coil is given to propose a novel coil structure. First, the co-simulation methods of Pspice and Maxwell are used. When the coupling coefficient of the resonant coil is different, the relationship between system transmission efficiency, output power, and frequency is analyzed. When the self-inductance of the resonant coil is different, the relationship between the performance and frequency of the system transmission is analyzed. Then, two-coil and three-coil structure models are built, and the parameters of the magnetic field of the coils are calculated and analyzed using the finite element method. In the end, a dual E-type simulation circuit model is used to optimize the design of the novel resonance coil. The co-simulation results show that the coupling coefficients of the two-coil, three-coil, and novel coil systems are 0.017, 0.17 and 0.0126, respectively. The power loss of the novel coil is 16.4 mW. There is an obvious improvement in the three-coil system, which shows that the magnetic leakage of the field and the energy coupling are relatively small. The new structure coil has better performance, and the load loss is lower; it can improve the system output power and transmission efficiency.

Enhanced ultrasound for advanced diagnostics, ultrasound tomography for volume limb imaging and prosthetic fitting

Science.gov (United States)

Anthony, Brian W.

2016-04-01

Ultrasound imaging methods hold the potential to deliver low-cost, high-resolution, operator-independent and nonionizing imaging systems - such systems couple appropriate algorithms with imaging devices and techniques. The increasing demands on general practitioners motivate us to develop more usable and productive diagnostic imaging equipment. Ultrasound, specifically freehand ultrasound, is a low cost and safe medical imaging technique. It doesn't expose a patient to ionizing radiation. Its safety and versatility make it very well suited for the increasing demands on general practitioners, or for providing improved medical care in rural regions or the developing world. However it typically suffers from sonographer variability; we will discuss techniques to address user variability. We also discuss our work to combine cylindrical scanning systems with state of the art inversion algorithms to deliver ultrasound systems for imaging and quantifying limbs in 3-D in vivo. Such systems have the potential to track the progression of limb health at a low cost and without radiation exposure, as well as, improve prosthetic socket fitting. Current methods of prosthetic socket fabrication remain subjective and ineffective at creating an interface to the human body that is both comfortable and functional. Though there has been recent success using methods like magnetic resonance imaging and biomechanical modeling, a low-cost, streamlined, and quantitative process for prosthetic cup design and fabrication has not been fully demonstrated. Medical ultrasonography may inform the design process of prosthetic sockets in a more objective manner. This keynote talk presents the results of progress in this area.

Photonic crystal Fano resonances for realizing optical switches, lasers and non-reciprocal elements

DEFF Research Database (Denmark)

Bekele, Dagmawi Alemayehu; Yu, Yi; Hu, Hao

2017-01-01

structure in combination with cavity-enhanced nonlinearity can be used to realize non-reciprocal transmission at ultra-low power and with large bandwidth. A novel type of laser structure, denoted a Fano laser, is discussed in which one of the mirrors is based on a Fano resonance. Finally, the design...

Tunable coupled nanomechanical resonators for single-electron transport

International Nuclear Information System (INIS)

Scheible, Dominik V; Erbe, Artur; Blick, Robert H

2002-01-01

Nano-electromechanical systems (NEMS) are ideal for sensor applications and ultra-sensitive force detection, since their mechanical degree of freedom at the nanometre scale can be combined with semiconductor nano-electronics. We present a system of coupled nanomechanical beam resonators in silicon which is mechanically fully Q-tunable ∼700-6000. This kind of resonator can also be employed as a mechanical charge shuttle via an insulated metallic island at the tip of an oscillating cantilever. Application of our NEMS as an electromechanical single-electron transistor (emSET) is introduced and experimental results are discussed. Three animation clips demonstrate the manufacturing process of the NEMS, the Q-tuning experiment and the concept of the emSET

Head and Neck Veins of the Mouse. A Magnetic Resonance, Micro Computed Tomography and High Frequency Color Doppler Ultrasound Study.

Directory of Open Access Journals (Sweden)

Marcello Mancini

Full Text Available To characterize the anatomy of the venous outflow of the mouse brain using different imaging techniques. Ten C57/black male mice (age range: 7-8 weeks were imaged with high-frequency Ultrasound, Magnetic Resonance Angiography and ex-vivo Microcomputed tomography of the head and neck. Under general anesthesia, Ultrasound of neck veins was performed with a 20 MHz transducer; head and neck Magnetic Resonance Angiography data were collected on 9.4 T or 7 T scanners, and ex-vivo Microcomputed tomography angiography was obtained by filling the vessels with a radiopaque inert silicone rubber compound. All procedures were approved by the local ethical committee. The dorsal intracranial venous system is quite similar in mice and humans. Instead, the mouse Internal Jugular Veins are tiny vessels receiving the sigmoid sinuses and tributaries from cerebellum, occipital lobe and midbrain, while the majority of the cerebral blood, i.e. from the olfactory bulbs and fronto-parietal lobes, is apparently drained through skull base connections into the External Jugular Vein. Three main intra-extracranial anastomoses, absent in humans, are: 1 the petrosquamous sinus, draining into the posterior facial vein, 2 the veins of the olfactory bulb, draining into the superficial temporal vein through a foramen of the frontal bone 3 the cavernous sinus, draining in the External Jugular Vein through a foramen of the sphenoid bone. The anatomical structure of the mouse cranial venous outflow as depicted by Ultrasound, Microcomputed tomography and Magnetic Resonance Angiography is different from humans, with multiple connections between intra- and extra-cranial veins.

Resonance saturation of the chiral couplings at next-to-leading order in 1/NC

International Nuclear Information System (INIS)

Rosell, Ignasi; Ruiz-Femenia, Pedro; Sanz-Cillero, Juan Jose

2009-01-01

The precision obtainable in phenomenological applications of chiral perturbation theory is currently limited by our lack of knowledge on the low-energy constants (LECs). The assumption that the most important contributions to the LECs come from the dynamics of the low-lying resonances, often referred to as the resonance saturation hypothesis, has stimulated the use of large-N C resonance Lagrangians in order to obtain explicit values for the LECs. We study the validity of the resonance saturation assumption at the next-to-leading order in the 1/N C expansion within the framework of resonance chiral theory. We find that, by imposing QCD short-distance constraints, the chiral couplings can be written in terms of the resonance masses and couplings and do not depend explicitly on the coefficients of the chiral operators in the Goldstone boson sector of resonance chiral theory. As we argue, this is the counterpart formulation of the resonance saturation statement in the context of the resonance Lagrangian. Going beyond leading order in the 1/N C counting allows us to keep full control of the renormalization scale dependence of the LEC estimates.

Resonance Spectrum Characteristics of Effective Electromechanical Coupling Coefficient of High-Overtone Bulk Acoustic Resonator

Directory of Open Access Journals (Sweden)

Jian Li

2016-09-01

Full Text Available A high-overtone bulk acoustic resonator (HBAR consisting of a piezoelectric film with two electrodes on a substrate exhibits a high quality factor (Q and multi-mode resonance spectrum. By analyzing the influences of each layer’s material and structure (thickness parameters on the effective electromechanical coupling coefficient (Keff2, the resonance spectrum characteristics of Keff2 have been investigated systematically, and the optimal design of HBAR has been provided. Besides, a device, corresponding to one of the theoretical cases studied, is fabricated and evaluated. The experimental results are basically consistent with the theoretical results. Finally, the effects of Keff2 on the function of the crystal oscillators constructed with HBARs are proposed. The crystal oscillators can operate in more modes and have a larger frequency hopping bandwidth by using the HBARs with a larger Keff2·Q.

Slow light enhanced optical nonlinearity in a silicon photonic crystal coupled-resonator optical waveguide.

Science.gov (United States)

Matsuda, Nobuyuki; Kato, Takumi; Harada, Ken-Ichi; Takesue, Hiroki; Kuramochi, Eiichi; Taniyama, Hideaki; Notomi, Masaya

2011-10-10

We demonstrate highly enhanced optical nonlinearity in a coupled-resonator optical waveguide (CROW) in a four-wave mixing experiment. Using a CROW consisting of 200 coupled resonators based on width-modulated photonic crystal nanocavities in a line defect, we obtained an effective nonlinear constant exceeding 10,000 /W/m, thanks to slow light propagation combined with a strong spatial confinement of light achieved by the wavelength-sized cavities.

Stochastic resonance in a single-mode laser driven by frequency modulated signal and coloured noises

Institute of Scientific and Technical Information of China (English)

Jin Guo-Xiang; Zhang Liang-Ying; Cao Li

2009-01-01

By adding frequency modulated signals to the intensity equation of gain-noise model of the single-mode laser driven by two coloured noises which are correlated, this paper uses the linear approximation method to calculate the power spectrum and signal-to-noise ratio (SNR) of the laser intensity. The results show that the SNR appears typical stochastic resonance with the variation of intensity of the pump noise and quantum noise. As the amplitude of a modulated signal has effects on the SNR, it shows suppression, monotone increasing, stochastic resonance, and multiple stochastic resonance with the variation of the frequency of a carrier signal and modulated signal.