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Sample records for ghz resonant mode

  1. A 10-GHz film-thickness-mode cavity optomechanical resonator

    NASA Astrophysics Data System (ADS)

    Han, Xu; Fong, King Y.; Tang, Hong X.

    2015-04-01

    We report on the advance of chip-scale cavity optomechanical resonators to beyond 10 GHz by exploiting the fundamental acoustic thickness mode of an aluminum nitride micro-disk. By engineering the mechanical anchor to minimize the acoustic loss, a quality factor of 1830 and hence a frequency-quality factor product of 1.9 × 1013 Hz are achieved in ambient air at room temperature. Actuated by strong piezo-electric force, the micro-disk resonator shows an excellent electro-optomechanical transduction efficiency. Our detailed analysis of the electro-optomechanical coupling allows identification and full quantification of various acoustic modes spanning from super-high to X-band microwave frequencies measured in the thin film resonator.

  2. Mode selection and resonator design studies of a 95 GHz, 100 kW, CW gyrotron

    SciTech Connect

    Vamshi Krishna, P.; Kartikeyan, M.V. E-mail: kartik@iitr.ernet.in; Thumm, M.

    2011-07-01

    In this paper, the mode selection procedure leading to the design and the cavity resonator design studies of a 95 GHz, 100 kW, CW Gyrotron will be presented, such a gyrotron will be used for specific ECRH/ECRIS applications. In this course all the suitable modes with design constraints within the limits of design goals are considered and finally the TE{sub 10.4} mode is chosen as the operating mode which is suitable for the design. Design constraints are carefully investigated, and starting currents are computed. (author)

  3. Kinetic instabilities in pulsed operation mode of a 14 GHz electron cyclotron resonance ion source

    SciTech Connect

    Tarvainen, O. Kalvas, T.; Koivisto, H.; Komppula, J.; Kronholm, R.; Laulainen, J.; Izotov, I.; Mansfeld, D.; Skalyga, V.

    2016-02-15

    The occurrence of kinetic plasma instabilities is studied in pulsed operation mode of a 14 GHz A-electron cyclotron resonance type electron cyclotron resonance ion source. It is shown that the temporal delay between the plasma breakdown and the appearance of the instabilities is on the order of 10-100 ms. The most important parameters affecting the delay are magnetic field strength and neutral gas pressure. It is demonstrated that kinetic instabilities limit the high charge state ion beam production in the unstable operating regime.

  4. Dielectric properties of dates at 2.45 GHz determined with a tunable single-mode resonant cavity.

    PubMed

    Ali, I A; al-Amri, A M; Dawoud, M M

    2000-01-01

    A tunable TM012-mode resonant cavity with an additional tuning mechanism and working at 2.45 GHz has been designed, fabricated and tested for determination of dielectric properties of dates. The cavity has a Q-factor > 5000, and a tuning mechanism which gives it more flexibility and controllability. The cavity has been used for determining the dielectric properties of Rezaiz, the most common type of dates used in the production of data juice in the Eastern Province of the Kingdom of Saudi Arabia. The dielectric constant for this type of dates was 4.6 +/- 0.16, and the loss factor was 0.21 +/- 0.03, at 8.75% moisture. These results are comparable with the dielectric properties of some other fruits, of similar composition, at the same moisture level.

  5. Towards a beyond 1 GHz solid-state nuclear magnetic resonance: External lock operation in an external current mode for a 500 MHz nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Takahashi, Masato; Ebisawa, Yusuke; Tennmei, Konosuke; Yanagisawa, Yoshinori; Hosono, Masami; Takasugi, Kenji; Hase, Takashi; Miyazaki, Takayoshi; Fujito, Teruaki; Nakagome, Hideki; Kiyoshi, Tsukasa; Yamazaki, Toshio; Maeda, Hideaki

    2012-10-01

    Achieving a higher magnetic field is important for solid-state nuclear magnetic resonance (NMR). But a conventional low temperature superconducting (LTS) magnet cannot exceed 1 GHz (23.5 T) due to the critical magnetic field. Thus, we started a project to replace the Nb3Sn innermost coil of an existing 920 MHz NMR (21.6 T) with a Bi-2223 high temperature superconducting (HTS) innermost coil. Unfortunately, the HTS magnet cannot be operated in persistent current mode; an external dc power supply is required to operate the NMR magnet, causing magnetic field fluctuations. These fluctuations can be stabilized by a field-frequency lock system based on an external NMR detection coil. We demonstrate here such a field-frequency lock system in a 500 MHz LTS NMR magnet operated in an external current mode. The system uses a 7Li sample in a microcoil as external NMR detection system. The required field compensation is calculated from the frequency of the FID as measured with a frequency counter. The system detects the FID signal, determining the FID frequency, and calculates the required compensation coil current to stabilize the sample magnetic field. The magnetic field was stabilized at 0.05 ppm/3 h for magnetic field fluctuations of around 10 ppm. This method is especially effective for a magnet with large magnetic field fluctuations. The magnetic field of the compensation coil is relatively inhomogeneous in these cases and the inhomogeneity of the compensation coil can be taken into account.

  6. 1.05-GHz CMOS oscillator based on lateral- field-excited piezoelectric AlN contour- mode MEMS resonators.

    PubMed

    Zuo, Chengjie; Van der Spiegel, Jan; Piazza, Gianluca

    2010-01-01

    This paper reports on the first demonstration of a 1.05-GHz microelectromechanical (MEMS) oscillator based on lateral-field-excited (LFE) piezoelectric AlN contourmode resonators. The oscillator shows a phase noise level of -81 dBc/Hz at 1-kHz offset frequency and a phase noise floor of -146 dBc/Hz, which satisfies the global system for mobile communications (GSM) requirements for ultra-high frequency (UHF) local oscillators (LO). The circuit was fabricated in the AMI semiconductor (AMIS) 0.5-microm complementary metaloxide- semiconductor (CMOS) process, with the oscillator core consuming only 3.5 mW DC power. The device overall performance has the best figure-of-merit (FoM) when compared with other gigahertz oscillators that are based on film bulk acoustic resonator (FBAR), surface acoustic wave (SAW), and CMOS on-chip inductor and capacitor (CMOS LC) technologies. A simple 2-mask process was used to fabricate the LFE AlN resonators operating between 843 MHz and 1.64 GHz with simultaneously high Q (up to 2,200) and kt 2 (up to 1.2%). This process further relaxes manufacturing tolerances and improves yield. All these advantages make these devices suitable for post-CMOS integrated on-chip direct gigahertz frequency synthesis in reconfigurable multiband wireless communications.

  7. GHz spurious mode free AlN lamb wave resonator with high figure of merit using one dimensional phononic crystal tethers

    NASA Astrophysics Data System (ADS)

    Wu, Guoqiang; Zhu, Yao; Merugu, Srinivas; Wang, Nan; Sun, Chengliang; Gu, Yuandong

    2016-07-01

    This letter reports a spurious mode free GHz aluminum nitride (AlN) lamb wave resonator (LWR) towards high figure of merit (FOM). One dimensional gourd-shape phononic crystal (PnC) tether with large phononic bandgaps is employed to reduce the acoustic energy dissipation into the substrate. The periodic PnC tethers are based on a 1 μm-thick AlN layer with 0.26 μm-thick Mo layer on top. A clean spectrum over a wide frequency range is obtained from the measurement, which indicates a wide-band suppression of spurious modes. Experimental results demonstrate that the fabricated AlN LWR has an insertion loss of 5.2 dB and a loaded quality factor (Q) of 1893 at 1.02 GHz measured in air. An impressive ratio of the resistance at parallel resonance (Rp) to the resistance at series resonance (Rs) of 49.8 dB is obtained, which is an indication of high FOM for LWR. The high Rp to Rs ratio is one of the most important parameters to design a radio frequency filter with steep roll-off.

  8. Dielectric properties of oil sands at 2.45 GHz with TE1,0,11 mode determined by a rectangular cavity resonator.

    PubMed

    Erdogan, Levent; Akyel, Cevdet; Ghannouchi, Fadhel M

    2011-01-01

    Oil obtained from oil sands resources constitute an important portion of the oil industry in Canada. Extraction of the bitumen from oil sands is very crucial process because of its cost and environmental impact. Microwave energy applicators by heating oil sands at microwave frequencies can be an excellent alternative to extract bitumen with the advantages of being potentially cost-effective and environmentally friendly method of extraction. In order to design and manufacture a microwave energy applicator, its dielectric properties must be known. In this study, as the first part of our ultimate microwave energy applicator project, in advance, the complex permittivity of oil sands was measured by using rectangular cavity resonator, designed and fabricated in Ecole Polytechnique de Montréal laboratories, at 2.45 GHz with TE1,0,1 mode. The accuracy of the permittivity measurement results obtained with the developed system was verified against those obtained using a commercial open-ended probe system as well the values of well known materials documented in open literature. Since there is no study found in the literature about the complex permittivity values of oil sands at 2.45 GHz, the present study would be of great help and important guide for those who plan to design and manufacture microwave energy applicators in order to extract the bitumen from the oil sands.

  9. 60 GHz Tapered Transmission Line Resonators

    DTIC Science & Technology

    2008-09-15

    DARPA TEAM program (contract no. DAAB07-02-1- L428 ), Motorola, and the UC-Micro program. 60 GHz Tapered Transmission Line Resonators by...0403427, wafer fabrication donation by STMicroelectronics, DARPA TEAM program (con- tract no. DAAB07-02-1- L428 ), Motorola, and the UC-Micro program. 1

  10. Large mode radius resonators

    NASA Technical Reports Server (NTRS)

    Harris, Michael R.

    1987-01-01

    Resonator configurations permitting operation with large mode radius while maintaining good transverse mode discrimination are considered. Stable resonators incorporating an intracavity telescope and unstable resonator geometries utilizing an output coupler with a Gaussian reflectivity profile are shown to enable large radius single mode laser operation. Results of heterodyne studies of pulsed CO2 lasers with large (11mm e sup-2 radius) fundamental mode sizes are presented demonstrating minimal frequency sweeping in accordance with the theory of laser-induced medium perturbations.

  11. Single-chip electron spin resonance detectors operating at 50 GHz, 92 GHz, and 146 GHz

    NASA Astrophysics Data System (ADS)

    Matheoud, Alessandro V.; Gualco, Gabriele; Jeong, Minki; Zivkovic, Ivica; Brugger, Jürgen; Rønnow, Henrik M.; Anders, Jens; Boero, Giovanni

    2017-05-01

    We report on the design and characterization of single-chip electron spin resonance (ESR) detectors operating at 50 GHz, 92 GHz, and 146 GHz. The core of the single-chip ESR detectors is an integrated LC-oscillator, formed by a single turn aluminum planar coil, a metal-oxide-metal capacitor, and two metal-oxide semiconductor field effect transistors used as negative resistance network. On the same chip, a second, nominally identical, LC-oscillator together with a mixer and an output buffer are also integrated. Thanks to the slightly asymmetric capacitance of the mixer inputs, a signal at a few hundreds of MHz is obtained at the output of the mixer. The mixer is used for frequency down-conversion, with the aim to obtain an output signal at a frequency easily manageable off-chip. The coil diameters are 120 μm, 70 μm, and 45 μm for the U-band, W-band, and the D-band oscillators, respectively. The experimental frequency noises at 100 kHz offset from the carrier are 90 Hz/Hz1/2, 300 Hz/Hz1/2, and 700 Hz/Hz1/2 at 300 K, respectively. The ESR spectra are obtained by measuring the frequency variations of the single-chip oscillators as a function of the applied magnetic field. The experimental spin sensitivities, as measured with a sample of α,γ-bisdiphenylene-β-phenylallyl (BDPA)/benzene complex, are 1 × 108 spins/Hz1/2, 4 × 107 spins/Hz1/2, 2 × 107 spins/Hz1/2 at 300 K, respectively. We also show the possibility to perform experiments up to 360 GHz by means of the higher harmonics in the microwave field produced by the integrated single-chip LC-oscillators.

  12. A 77-118 GHz RESONANCE-FREE SEPTUM POLARIZER

    SciTech Connect

    Chen, Yen-Lin; Chiueh, Tzihong; Teng, Hsiao-Feng

    2014-03-01

    Measurements of polarized radiation often reveal specific physical properties of emission sources, such as the strengths and orientations of magnetic fields offered by synchrotron radiation and Zeeman line emission, and the electron density distribution caused by free-free emission. Polarization-capable, millimeter/sub-millimeter telescopes are normally equipped with either septum polarizers or ortho-mode transducers (OMT) to detect polarized radiation. Though the septum polarizer is limited to a significantly narrower bandwidth than the OMT, it possesses advantageous features unparalleled by the OMT when it comes to determining astronomical polarization measurements. We design an extremely wide-band circular waveguide septum polarizer, covering 42% bandwidth, from 77 GHz to 118 GHz, without any undesired resonance, challenging the conventional bandwidth limit. Stokes parameters, constructed from the measured data between 77 GHz and 115 GHz, show that the leakage from I to Q and U is below ±2%, and the Q – U mutual leakage is below ±1%. Such a performance is comparable to other modern polarizers, but the bandwidth of this polarizer can be at least twice as wide. This extremely wide-band design removes the major weakness of the septum polarizer and opens up a new window for future astronomical polarization measurements.

  13. A 77-118 GHz Resonance-free Septum Polarizer

    NASA Astrophysics Data System (ADS)

    Chen, Yen-Lin; Chiueh, Tzihong; Teng, Hsiao-Feng

    2014-03-01

    Measurements of polarized radiation often reveal specific physical properties of emission sources, such as the strengths and orientations of magnetic fields offered by synchrotron radiation and Zeeman line emission, and the electron density distribution caused by free-free emission. Polarization-capable, millimeter/sub-millimeter telescopes are normally equipped with either septum polarizers or ortho-mode transducers (OMT) to detect polarized radiation. Though the septum polarizer is limited to a significantly narrower bandwidth than the OMT, it possesses advantageous features unparalleled by the OMT when it comes to determining astronomical polarization measurements. We design an extremely wide-band circular waveguide septum polarizer, covering 42% bandwidth, from 77 GHz to 118 GHz, without any undesired resonance, challenging the conventional bandwidth limit. Stokes parameters, constructed from the measured data between 77 GHz and 115 GHz, show that the leakage from I to Q and U is below ±2%, and the Q - U mutual leakage is below ±1%. Such a performance is comparable to other modern polarizers, but the bandwidth of this polarizer can be at least twice as wide. This extremely wide-band design removes the major weakness of the septum polarizer and opens up a new window for future astronomical polarization measurements.

  14. Force detected electron spin resonance at 94 GHz.

    PubMed

    Cruickshank, Paul A S; Smith, Graham M

    2007-01-01

    Force detected electron spin resonance (FDESR) detects the presence of unpaired electrons in a sample by measuring the change in force on a mechanical resonator as the magnetization of the sample is modulated under magnetic resonance conditions. The magnetization is coupled to the resonator via a magnetic field gradient. It has been used to both detect and image distributions of electron spins, and it offers both extremely high absolute sensitivity and high spatial imaging resolution. However, compared to conventional induction mode ESR the technique also has a comparatively poor concentration sensitivity and it introduces complications in interpreting and combining both spectroscopy and imaging. One method to improve both sensitivity and spectral resolution is to operate in high magnetic fields in order to increase the sample magnetization and g-factor resolution. In this article we present FDESR measurements on the organic conductor (fluoranthene)(2)PF(6) at 3.2 T, with a corresponding millimeter-wave frequency of 93.5 GHz, which we believe are the highest field results for FDESR reported in the literature to date. A magnet-on-cantilever approach was used, with a high-anisotropy microwave ferrite as the gradient source and employing cyclic saturation to modulate the magnetization at the cantilever fundamental frequency.

  15. Experimental results of superimposing 9.9 GHz extraordinary mode microwaves on 2.45 GHz ECRIS plasma.

    PubMed

    Nishiokada, Takuya; Nagaya, Tomoki; Hagino, Shogo; Otsuka, Takuro; Muramatsu, Masayuki; Sato, Fuminobu; Kitagawa, Atsushi; Kato, Yushi

    2016-02-01

    Efficient production of multicharged ions has been investigated on the tandem-type ECRIS in Osaka University. According to the consideration of the accessibility conditions of microwaves to resonance and cutoff regions, it was suggested that the upper hybrid resonance (UHR) heating contributed to enhancement of ion beam intensity. In order to enhance multicharged ion beams efficiently, injecting higher frequency microwave with extraordinary (X-mode) toward UHR region has been tried. In this study, 2.45 GHz frequency microwaves are used for conventional ECR discharge, and 9.9 GHz frequency microwaves with X-mode are superimposed for UHR heating. The effects of additive microwave injection are investigated experimentally in terms of plasma parameters and electron energy distribution function (EEDF) measured by Langmuir probe and ion beam current. As the results show, it is confirmed that the electrons in the high energy region are affected by 9.9 GHz X-mode microwave injection from the detailed analysis of EEDF.

  16. Experimental results of superimposing 9.9 GHz extraordinary mode microwaves on 2.45 GHz ECRIS plasma

    NASA Astrophysics Data System (ADS)

    Nishiokada, Takuya; Nagaya, Tomoki; Hagino, Shogo; Otsuka, Takuro; Muramatsu, Masayuki; Sato, Fuminobu; Kitagawa, Atsushi; Kato, Yushi

    2016-02-01

    Efficient production of multicharged ions has been investigated on the tandem-type ECRIS in Osaka University. According to the consideration of the accessibility conditions of microwaves to resonance and cutoff regions, it was suggested that the upper hybrid resonance (UHR) heating contributed to enhancement of ion beam intensity. In order to enhance multicharged ion beams efficiently, injecting higher frequency microwave with extraordinary (X-mode) toward UHR region has been tried. In this study, 2.45 GHz frequency microwaves are used for conventional ECR discharge, and 9.9 GHz frequency microwaves with X-mode are superimposed for UHR heating. The effects of additive microwave injection are investigated experimentally in terms of plasma parameters and electron energy distribution function (EEDF) measured by Langmuir probe and ion beam current. As the results show, it is confirmed that the electrons in the high energy region are affected by 9.9 GHz X-mode microwave injection from the detailed analysis of EEDF.

  17. Experimental results of superimposing 9.9 GHz extraordinary mode microwaves on 2.45 GHz ECRIS plasma

    SciTech Connect

    Nishiokada, Takuya Nagaya, Tomoki; Hagino, Shogo; Otsuka, Takuro; Sato, Fuminobu; Kato, Yushi; Muramatsu, Masayuki; Kitagawa, Atsushi

    2016-02-15

    Efficient production of multicharged ions has been investigated on the tandem-type ECRIS in Osaka University. According to the consideration of the accessibility conditions of microwaves to resonance and cutoff regions, it was suggested that the upper hybrid resonance (UHR) heating contributed to enhancement of ion beam intensity. In order to enhance multicharged ion beams efficiently, injecting higher frequency microwave with extraordinary (X-mode) toward UHR region has been tried. In this study, 2.45 GHz frequency microwaves are used for conventional ECR discharge, and 9.9 GHz frequency microwaves with X-mode are superimposed for UHR heating. The effects of additive microwave injection are investigated experimentally in terms of plasma parameters and electron energy distribution function (EEDF) measured by Langmuir probe and ion beam current. As the results show, it is confirmed that the electrons in the high energy region are affected by 9.9 GHz X-mode microwave injection from the detailed analysis of EEDF.

  18. 24 GHz microwave mode converter optimized for superconducting ECR ion source SECRAL

    SciTech Connect

    Guo, J. W.; Sun, L.; Zhang, X. Z.; Lu, W.; Zhang, W. H.; Feng, Y. C.; Zhao, H. W.; Niu, X. J.

    2016-02-15

    Over-sized round waveguide with a diameter about Ø33.0 mm excited in the TE{sub 01} mode has been widely adopted for microwave transmission and coupling to the ECR (Electron Cyclotron Resonance) plasma with the superconducting ECR ion sources operating at 24 or 28 GHz, such as SECRAL and VENUS. In order to study the impact of different microwave modes on ECRH (Electron Cyclotron Resonance Heating) efficiency and especially the production of highly charged ions, a set of compact and efficient TE{sub 01}-HE{sub 11} mode conversion and coupling system applicable to 24 GHz SECRAL whose overall length is 330 mm has been designed, fabricated and tested. Good agreements between off-line tests and calculation results have been achieved, which indicates the TE{sub 01}-HE{sub 11} converter meets the application design. The detailed results of the optimized coupling system will be presented in the paper.

  19. 24 GHz microwave mode converter optimized for superconducting ECR ion source SECRAL.

    PubMed

    Guo, J W; Sun, L; Niu, X J; Zhang, X Z; Lu, W; Zhang, W H; Feng, Y C; Zhao, H W

    2016-02-01

    Over-sized round waveguide with a diameter about Ø33.0 mm excited in the TE01 mode has been widely adopted for microwave transmission and coupling to the ECR (Electron Cyclotron Resonance) plasma with the superconducting ECR ion sources operating at 24 or 28 GHz, such as SECRAL and VENUS. In order to study the impact of different microwave modes on ECRH (Electron Cyclotron Resonance Heating) efficiency and especially the production of highly charged ions, a set of compact and efficient TE01-HE11 mode conversion and coupling system applicable to 24 GHz SECRAL whose overall length is 330 mm has been designed, fabricated and tested. Good agreements between off-line tests and calculation results have been achieved, which indicates the TE01-HE11 converter meets the application design. The detailed results of the optimized coupling system will be presented in the paper.

  20. Startup and mode competition in a 420 GHz gyrotron

    NASA Astrophysics Data System (ADS)

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

    2017-09-01

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

  1. Electromagnetic resonant modes of dielectric sphere bilayers

    SciTech Connect

    Andueza, A. Pérez-Conde, J.; Sevilla, J.

    2015-05-28

    Sphere bilayers have been proposed as promising structures for electromagnetic management in photonic crystal devices. These arrangements are made of two intertwined subsets of spheres of different size and refractive index, one subset filling the interstitial sites of the other. We present a systematic study of the electromagnetic resonant modes of the bilayers, in comparison with those of the constituent subsets of spheres. Three samples were built with glass and Teflon spheres and their transmission spectra measured in the microwave range (10–25 GHz). Simulations with finite integration time-domain method are in good agreement with experiments. Results show that the bilayer presents the same resonances as one of the subsets but modified by the presence of the other in its resonant frequencies and in the electric field distributions. As this distortion is not very large, the number of resonances in a selected spectral region is determined by the dominant subset. The degree of freedom that offers the bilayer could be useful to fine tune the resonances of the structure for different applications. A map of modes useful to guide this design is also presented. Scale invariance of Maxwell equations allows the translation of these results in the microwave range to the visible region; hence, some possible applications are discussed in this framework.

  2. Resonance mode in DNA dynamics

    NASA Astrophysics Data System (ADS)

    Zdravkovic, S.; Sataric, M. V.

    2007-11-01

    In this article we use Peyrard-Bishop-Dauxois model (PBD) to study the nonlinear oscillations of DNA nucleotides of extremely high amplitude (EHA) leading to unzipping of DNA chain in the context of the process of replication. We give arguments that the EHA mode is nothing but the resonance mode (RM). We launched an idea about how molecular mechano-chemical energy transduction can be the origin of the RM. We compared some parameters of the solitonic wave in DNA in resonant and non-resonant regime.

  3. Whispering Gallery Mode Optomechanical Resonator

    NASA Technical Reports Server (NTRS)

    Aveline, David C.; Strekalov, Dmitry V.; Yu, Nan; Yee, Karl Y.

    2012-01-01

    Great progress has been made in both micromechanical resonators and micro-optical resonators over the past decade, and a new field has recently emerged combining these mechanical and optical systems. In such optomechanical systems, the two resonators are strongly coupled with one influencing the other, and their interaction can yield detectable optical signals that are highly sensitive to the mechanical motion. A particularly high-Q optical system is the whispering gallery mode (WGM) resonator, which has many applications ranging from stable oscillators to inertial sensor devices. There is, however, limited coupling between the optical mode and the resonator s external environment. In order to overcome this limitation, a novel type of optomechanical sensor has been developed, offering great potential for measurements of displacement, acceleration, and mass sensitivity. The proposed hybrid device combines the advantages of all-solid optical WGM resonators with high-quality micro-machined cantilevers. For direct access to the WGM inside the resonator, the idea is to radially cut precise gaps into the perimeter, fabricating a mechanical resonator within the WGM. Also, a strategy to reduce losses has been developed with optimized design of the cantilever geometry and positions of gap surfaces.

  4. 5.4 GHz Lamb Wave Resonator on LiNbO3 Thin Crystal Plate and Its Application

    NASA Astrophysics Data System (ADS)

    Kadota, Michio; Ogami, Takashi

    2011-07-01

    A cognitive radio system operating at frequencies from 400 MHz to 6 GHz requires tunable filters with a wide variable frequency range. Wide band resonators are required to realize such tunable filters consisting of resonators. However, it is difficult to fabricate a very high frequency and wide band resonator, such as 6 GHz and wider than 10%, respectively. The first antisymmetric (A1) mode of a Lamb wave on a LiNbO3 thin plate or film having a high velocity and a large electromechanical coupling factor is a suitable wave for fabricating an ultrawide band and high frequency resonator. This time, we attempted to fabricate a higher frequency Lamb wave resonator on a thin LiNbO3 single-crystal plate instead of the LiNbO3 film, though it has been considered difficult to form a very thin LiNbO3 crystal plate. A new one-port Lamb wave resonator showed a high frequency in the 5 GHz range, a wide bandwidth of 12%, and a high impedance ratio of 62 dB at resonant and antiresonant frequencies. Moreover, we applied the resonator to a ladder-type tunable filter, and obtained the tunable range of 9% from 5.58 to 6.06 GHz theoretically.

  5. A 250-GHz CARM (Cyclotron Auto Resonance Maser) oscillator experiment driven by an induction linac

    SciTech Connect

    Caplan, M.; Kulke, B.; Bubp, D.G. ); McDermott, D.; Luhmann, N. )

    1990-09-14

    A 250-GHz Cyclotron Auto Resonance Maser (CARM) oscillator has been designed and constructed and will be tested using a 1-kA, 2-MeV electron beam produced by the induction linac at the Accelerator Research Center (ARC) facility of Lawrence Livermore National Laboratory (LLNL). The oscillator circuit was made to operate in the TE{sub 11} mode at ten times cutoff using waveguide Bragg reflectors to create an external cavity Q of 8000. Theory predicts cavity fill times of less than 30 ns (pulse length) and efficiencies approaching 20% is sufficiently low transverse electron velocity spreads are maintained (2%).

  6. Active mode locking at 50 GHz repetition frequency by half-frequency modulation of monolithic semiconductor lasers integrated with electroabsorption modulators

    NASA Astrophysics Data System (ADS)

    Sato, Kenji; Kotaka, Isamu; Kondo, Yasuhiro; Yamamoto, Mitsuo

    1996-10-01

    Active mode locking achieved at a 50 GHz repetition frequency by modulation at half (25 GHz) the cavity resonance frequency using a monolithic mode-locked InGaAsP laser integrated with an electroabsorption modulator is described. A pulse width of around 3 ps and a high suppression ratio of more than 33 dB of the intensity modulation at the driving frequency are obtained.

  7. A quasioptical resonant-tunneling-diode oscillator operating above 200 GHz

    NASA Technical Reports Server (NTRS)

    Brown, E. R.; Parker, C. D.; Molvar, K. M.; Calawa, A. R.; Manfra, M. J.

    1992-01-01

    We have fabricated and characterized a quasioptically stabilized resonant-tunneling-diode (RTD) oscillator having attractive performance characteristics for application as a radiometric local oscillator. The fundamental frequency of the oscillator is tunable from about 200 to 215 GHz, the instantaneous linewidth is between 10 and 20 kHz, and the output power across the tuning band is about 50 micro-W. The narrow linewidth and fine tuning of the frequency are made possible by a scanning semiconfocal open cavity which acts as the high-Q resonator for the oscillator. The cavity is compact, portable, and insensitive to vibration and temperature variation. The total dc power consumption (RTD plus bias supply) is only 10 mW. The present oscillator provides the highest power obtained to date from an RTD above 200 GHz. We attribute this partly to the use of the quasioptical resonator, but primarily to the quality of the RTD. It is fabricated from the In(0.53)Ga(0.47)As/AlAs materials system, which historically has yielded the best overall resonant-tunneling characteristics of any material system. The RTD active area is 4 sq microns, and the room-temperature peak current density and peak-to-valley current ratio are 2.5x10(exp 5) A cm(exp -2) and 9, respectively. The RTD is mounted in a WR-3 standard-height rectangular waveguide and is contacted across the waveguide by a fine wire that protrudes through a via hole in a Si3N4 'honeycomb' overlayer. We estimate that the theoretical maximum frequency of oscillation of this RTD is approximately 1.1 THz, and that scaled-down versions of the same quasioptical oscillator design should operate in a fundamental mode up to frequencies of at least 500 GHz.

  8. A quasioptical resonant-tunneling-diode oscillator operating above 200 GHz

    NASA Technical Reports Server (NTRS)

    Brown, E. R.; Parker, C. D.; Molvar, K. M.; Calawa, A. R.; Manfra, M. J.

    1992-01-01

    We have fabricated and characterized a quasioptically stabilized resonant-tunneling-diode (RTD) oscillator having attractive performance characteristics for application as a radiometric local oscillator. The fundamental frequency of the oscillator is tunable from about 200 to 215 GHz, the instantaneous linewidth is between 10 and 20 kHz, and the output power across the tuning band is about 50 micro-W. The narrow linewidth and fine tuning of the frequency are made possible by a scanning semiconfocal open cavity which acts as the high-Q resonator for the oscillator. The cavity is compact, portable, and insensitive to vibration and temperature variation. The total dc power consumption (RTD plus bias supply) is only 10 mW. The present oscillator provides the highest power obtained to date from an RTD above 200 GHz. We attribute this partly to the use of the quasioptical resonator, but primarily to the quality of the RTD. It is fabricated from the In(0.53)Ga(0.47)As/AlAs materials system, which historically has yielded the best overall resonant-tunneling characteristics of any material system. The RTD active area is 4 sq microns, and the room-temperature peak current density and peak-to-valley current ratio are 2.5x10(exp 5) A cm(exp -2) and 9, respectively. The RTD is mounted in a WR-3 standard-height rectangular waveguide and is contacted across the waveguide by a fine wire that protrudes through a via hole in a Si3N4 'honeycomb' overlayer. We estimate that the theoretical maximum frequency of oscillation of this RTD is approximately 1.1 THz, and that scaled-down versions of the same quasioptical oscillator design should operate in a fundamental mode up to frequencies of at least 500 GHz.

  9. Nonlinear optical whispering gallery mode resonators

    NASA Technical Reports Server (NTRS)

    Ilchenko, Vladimir (Inventor); Matsko, Andrey B. (Inventor); Savchenkov, Anatoliy (Inventor); Maleki, Lutfollah (Inventor)

    2005-01-01

    Whispering gallery mode (WGM) optical resonators comprising nonlinear optical materials, where the nonlinear optical material of a WGM resonator includes a plurality of sectors within the optical resonator and nonlinear coefficients of two adjacent sectors are oppositely poled.

  10. Graded-index whispering gallery mode resonators

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy (Inventor); Maleki, Lutfollah (Inventor); Ilchenko, Vladimir (Inventor); Matsko, Andrey B. (Inventor)

    2005-01-01

    Whispering gallery mode optical resonators which have spatially-graded refractive indices. In one implementation, the refractive index spatially increases with a distance from an exterior surface of such a resonator towards an interior of the resonator to produce substantially equal spectral separations for different whispering gallery modes. An optical coupler may be used with such a resonator to provide proper optical coupling.

  11. 3.4 GHz composite thin film bulk acoustic wave resonator for miniaturized atomic clocks

    SciTech Connect

    Artieda, Alvaro; Muralt, Paul

    2011-06-27

    Triple layer SiO{sub 2}/AlN/SiO{sub 2} composite thin film bulk acoustic wave resonators (TFBARs) were studied for applications in atomic clocks. The TFBAR's were tuned to 3.4 GHz, corresponding to half the hyperfine splitting of the ground state of rubidium {sup 87}Rb atoms. The quality factor (Q) was equal to 2300 and the temperature coefficient of the resonance frequency f{sub r} amounted to 1.5 ppm/K. A figure of merit Qf{sub r} of {approx} 0.8 x 10{sup 13} Hz and a thickness mode coupling factor of 1% were reached. Such figures are ideal for frequency sources in an oscillator circuit that tracks the optical signal in atomic clocks.

  12. 3.4 GHz composite thin film bulk acoustic wave resonator for miniaturized atomic clocks

    NASA Astrophysics Data System (ADS)

    Artieda, Alvaro; Muralt, Paul

    2011-06-01

    Triple layer SiO2/AlN/SiO2 composite thin film bulk acoustic wave resonators (TFBARs) were studied for applications in atomic clocks. The TFBAR's were tuned to 3.4 GHz, corresponding to half the hyperfine splitting of the ground state of rubidium 87Rb atoms. The quality factor (Q) was equal to 2300 and the temperature coefficient of the resonance frequency fr amounted to 1.5 ppm/K. A figure of merit Qfr of ˜ 0.8 × 1013 Hz and a thickness mode coupling factor of 1% were reached. Such figures are ideal for frequency sources in an oscillator circuit that tracks the optical signal in atomic clocks.

  13. A dual-mode microwave resonator for double electron-electron spin resonance spectroscopy at W-band microwave frequencies

    NASA Astrophysics Data System (ADS)

    Tkach, Igor; Sicoli, Giuseppe; Höbartner, Claudia; Bennati, Marina

    2011-04-01

    We present a dual-mode resonator operating at/near 94 GHz (W-band) microwave frequencies and supporting two microwave modes with the same field polarization at the sample position. Numerical analysis shows that the frequencies of both modes as well as their frequency separation can be tuned in a broad range up to GHz. The resonator was constructed to perform pulsed ELDOR experiments with a variable separation of "pump" and "detection" frequencies up to Δ ν = 350 MHz. To examine its performance, test ESE/PELDOR experiments were performed on a representative biradical system.

  14. White-Light Whispering-Gallery-Mode Optical Resonators

    NASA Technical Reports Server (NTRS)

    Matsko, Andrey; Savchenkov, Anatoliy; Maleki, Lute

    2006-01-01

    Whispering-gallery-mode (WGM) optical resonators can be designed to exhibit continuous spectra over wide wavelength bands (in effect, white-light spectra), with ultrahigh values of the resonance quality factor (Q) that are nearly independent of frequency. White-light WGM resonators have potential as superior alternatives to (1) larger, conventional optical resonators in ring-down spectroscopy, and (2) optical-resonator/electro-optical-modulator structures used in coupling of microwave and optical signals in atomic clocks. In these and other potential applications, the use of white-light WGM resonators makes it possible to relax the requirement of high-frequency stability of lasers, thereby enabling the use of cheaper lasers. In designing a white-light WGM resonator, one exploits the fact that the density of the mode spectrum increases predictably with the thickness of the resonator disk. By making the resonator disk sufficiently thick, one can make the frequency differences between adjacent modes significantly less than the spectral width of a single mode, so that the spectral peaks of adjacent modes overlap, making the resonator spectrum essentially continuous. Moreover, inasmuch as the Q values of the various modes are determined primarily by surface Rayleigh scattering that does not depend on mode numbers, all the modes have nearly equal Q. By use of a proper coupling technique, one can ensure excitation of a majority of the modes. For an experimental demonstration of a white-light WGM resonator, a resonator disk 0.5-mm thick and 5 mm in diameter was made from CaF2. The shape of the resonator and the fiberoptic coupling arrangement were as shown in Figure 1. The resonator was excited with laser light having a wavelength of 1,320 nm and a spectral width of 4 kHz. The coupling efficiency exceeded 80 percent at any frequency to which the laser could be set in its tuning range, which was >100-GHz wide. The resonator response was characterized by means of ring

  15. Mode converters for generating the HE11 (near-Gaussian) mode from gyrotron TEOn modes at 140 GHz

    NASA Astrophysics Data System (ADS)

    Thumm, M.; Sturm, H.

    1985-11-01

    The structure of wall perturbations (superposition of 2 or 3 different periods) in rippled wall mode converters and the curvature distribution in bent smooth-walled TEO1-to-TM11 mode transducers were optimized by numerically solving the corresponding coupled-mode differential equations. Computer-aided optimization of circumferentially corrugated mode converters was achieved with a scattering matrix code employing the modal field expansion technique. In all cases the predicted overall efficiency of the complete mode converter system from Sigma TEOn (predominantly TEO3) to HE11 in the desired mode is 90% to 92% (ohmic attenuation is included). Low-power measurements on the efficiency of a 140 GHz TEO1-to-TM11 mode transducer (ao = 13.9 mm) are in excellent agreement with the predicted value of 95.2% (including ohmic attenuation).

  16. Oscillations up to 712 GHz in InAs/AlSb resonant-tunneling diodes

    NASA Technical Reports Server (NTRS)

    Brown, E. R.; Parker, C. D.; Mahoney, L. J.; Molvar, K. M.; Soderstrom, J. R.

    1991-01-01

    Oscillations have been obtained at frequencies from 100 to 712 GHz in InAs/AlSb double-barrier resonant-tunneling diodes at room temperature. The measured power density at 360 GHz was 90 W/sq cm, which is 50 times that generated by GaAs/AlAs diodes at essentially the same frequency. The oscillation at 712 GHz represents the highest frequency reported to date from a solid-state electronic oscillator at room temperature.

  17. Thermal Properties of Whispering Gallery Mode Resonators

    DTIC Science & Technology

    2014-12-22

    F01m 298 (Rev 8/98) Prescribed by ANSI Std. Z39.18 ABSTRACT Number of Papers published in peer-reviewed journals: Thermal Properties of Whispering...Gallery Mode Resonators Report Title In this project, we studied the thermal properties of ultra-high-quality whispering-gallery-mode microtoroid...resonators. More specifically, we measured the thermal relaxation time of the resonator to estimate the response time of the resonator based infrared (IR

  18. Mechanical detection and mode shape imaging of vibrational modes of micro and nanomechanical resonators by dynamic force microscopy

    NASA Astrophysics Data System (ADS)

    Paulo, A. S.; Black, J.; García-Sanchez, D.; Esplandiu, M. J.; Aguasca, A.; Bokor, J.; Perez-Murano, F.; Bachtold, A.

    2008-03-01

    We describe a method based on the use of higher order bending modes of the cantilever of a dynamic force microscope to characterize vibrations of micro and nanomechanical resonators at arbitrarily large resonance frequencies. Our method consists on using a particular cantilever eigenmode for standard feedback control in amplitude modulation operation while another mode is used for detecting and imaging the resonator vibration. In addition, the resonating sample device is driven at or near its resonance frequency with a signal modulated in amplitude at a frequency that matches the resonance of the cantilever eigenmode used for vibration detection. In consequence, this cantilever mode is excited with an amplitude proportional to the resonator vibration, which is detected with an external lock-in amplifier. We show two different application examples of this method. In the first one, acoustic wave vibrations of a film bulk acoustic resonator around 1.6 GHz are imaged. In the second example, bending modes of carbon nanotube resonators up to 3.1 GHz are characterized. In both cases, the method provides subnanometer-scale sensitivity and the capability of providing otherwise inaccessible information about mechanical resonance frequencies, vibration amplitude values and mode shapes.

  19. All-optical Photonic Oscillator with High-Q Whispering Gallery Mode Resonators

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy A.; Matsko, Andrey B.; Strekalov, Dmitry; Mohageg, Makan; Iltchenko, Vladimir S.; Maleki, Lute

    2004-01-01

    We demonstrated low threshold optical photonic hyper-parametric oscillator in a high-Q 10(exp 10) CaF2 whispering gallery mode resonator which generates stable 8.5 GHz signal. The oscillations result from the resonantly enhanced four wave mixing occurring due to Kerr nonlinearity of the material.

  20. Control system renewal for efficient operation in RIKEN 18 GHz electron cyclotron resonance ion source

    SciTech Connect

    Uchiyama, A. Ozeki, K.; Higurashi, Y.; Kidera, M.; Komiyama, M.; Nakagawa, T.

    2016-02-15

    A RIKEN 18 GHz electron cyclotron resonance ion source (18 GHz ECRIS) is used as an external ion source at the Radioactive Ion Beam Factory (RIBF) accelerator complex to produce an intense beam of medium-mass heavy ions (e.g., Ca and Ar). In most components that comprise the RIBF, the control systems (CSs) are integrated by the Experimental Physics and Industrial Control System (EPICS). On the other hand, a non-EPICS-based system has hardwired controllers, and it is used in the 18 GHz ECRIS CS as an independent system. In terms of efficient and effective operation, the 18 GHz ECRIS CS as well as the RIBF CS should be renewed using EPICS. Therefore, we constructed an 18 GHz ECRIS CS by using programmable logic controllers with embedded EPICS technology. In the renewed system, an operational log system was developed as a new feature, for supporting of the 18 GHz ECRIS operation.

  1. Control system renewal for efficient operation in RIKEN 18 GHz electron cyclotron resonance ion source

    NASA Astrophysics Data System (ADS)

    Uchiyama, A.; Ozeki, K.; Higurashi, Y.; Kidera, M.; Komiyama, M.; Nakagawa, T.

    2016-02-01

    A RIKEN 18 GHz electron cyclotron resonance ion source (18 GHz ECRIS) is used as an external ion source at the Radioactive Ion Beam Factory (RIBF) accelerator complex to produce an intense beam of medium-mass heavy ions (e.g., Ca and Ar). In most components that comprise the RIBF, the control systems (CSs) are integrated by the Experimental Physics and Industrial Control System (EPICS). On the other hand, a non-EPICS-based system has hardwired controllers, and it is used in the 18 GHz ECRIS CS as an independent system. In terms of efficient and effective operation, the 18 GHz ECRIS CS as well as the RIBF CS should be renewed using EPICS. Therefore, we constructed an 18 GHz ECRIS CS by using programmable logic controllers with embedded EPICS technology. In the renewed system, an operational log system was developed as a new feature, for supporting of the 18 GHz ECRIS operation.

  2. Using Whispering-Gallery-Mode Resonators for Refractometry

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    A method of determining the refractive and absorptive properties of optically transparent materials involves a combination of theoretical and experimental analysis of electromagnetic responses of whispering-gallery-mode (WGM) resonator disks made of those materials. The method was conceived especially for use in studying transparent photorefractive materials, for which purpose this method affords unprecedented levels of sensitivity and accuracy. The method is expected to be particularly useful for measuring temporally varying refractive and absorptive properties of photorefractive materials at infrared wavelengths. Still more particularly, the method is expected to be useful for measuring drifts in these properties that are so slow that, heretofore, the properties were assumed to be constant. The basic idea of the method is to attempt to infer values of the photorefractive properties of a material by seeking to match (1) theoretical predictions of the spectral responses (or selected features thereof) of a WGM of known dimensions made of the material with (2) the actual spectral responses (or selected features thereof). Spectral features that are useful for this purpose include resonance frequencies, free spectral ranges (differences between resonance frequencies of adjacently numbered modes), and resonance quality factors (Q values). The method has been demonstrated in several experiments, one of which was performed on a WGM resonator made from a disk of LiNbO3 doped with 5 percent of MgO. The free spectral range of the resonator was approximately equal to 3.42 GHz at wavelengths in the vicinity of 780 nm, the smallest full width at half maximum of a mode was approximately equal to 50 MHz, and the thickness of the resonator in the area of mode localization was 30 microns. In the experiment, laser power of 9 mW was coupled into the resonator with an efficiency of 75 percent, and the laser was scanned over a frequency band 9 GHz wide at a nominal wavelength of

  3. Results of RIKEN superconducting electron cyclotron resonance ion source with 28 GHz.

    PubMed

    Higurashi, Y; Ohnishi, J; Nakagawa, T; Haba, H; Tamura, M; Aihara, T; Fujimaki, M; Komiyama, M; Uchiyama, A; Kamigaito, O

    2012-02-01

    We measured the beam intensity of highly charged heavy ions and x-ray heat load for RIKEN superconducting electron cyclotron resonance ion source with 28 GHz microwaves under the various conditions. The beam intensity of Xe(20+) became maximum at B(min) ∼ 0.65 T, which was ∼65% of the magnetic field strength of electron cyclotron resonance (B(ECR)) for 28 GHz microwaves. We observed that the heat load of x-ray increased with decreasing gas pressure and field gradient at resonance zone. It seems that the beam intensity of highly charged heavy ions with 28 GHz is higher than that with 18 GHz at same RF power.

  4. 200-GHz and 50-GHz AWG channelized linewidth dependent transmission of weak-resonant-cavity FPLD injection-locked by spectrally sliced ASE.

    PubMed

    Lin, Gong-Ru; Cheng, Tzu-Kang; Chi, Yu-Chieh; Lin, Gong-Cheng; Wang, Hai-Lin; Lin, Yi-Hong

    2009-09-28

    In a weak-resonant-cavity Fabry-Perot laser diode (WRC-FPLD) based DWDM-PON system with an array-waveguide-grating (AWG) channelized amplified spontaneous emission (ASE) source located at remote node, we study the effect of AWG filter bandwidth on the transmission performances of the 1.25-Gbit/s directly modulated WRC-FPLD transmitter under the AWG channelized ASE injection-locking. With AWG filters of two different channel spacings at 50 and 200 GHz, several characteristic parameters such as interfered reflection, relatively intensity noise, crosstalk reduction, side-mode-suppressing ratio and power penalty of BER effect of the WRC-FPLD transmitted data are compared. The 200-GHz AWG filtered ASE injection minimizes the noises of WRC-FPLD based ONU transmitter, improving the power penalty of upstream data by -1.6 dB at BER of 10(-12). In contrast, the 50-GHz AWG channelized ASE injection fails to promote better BER but increases the power penalty by + 1.5 dB under back-to-back transmission. A theoretical modeling elucidates that the BER degradation up to 4 orders of magnitude between two injection cases is mainly attributed to the reduction on ASE injection linewidth, since which concurrently degrades the signal-to-noise and extinction ratios of the transmitted data stream.

  5. Microelectromechanical filter formed from parallel-connected lattice networks of contour-mode resonators

    DOEpatents

    Wojciechowski, Kenneth E; Olsson, III, Roy H; Ziaei-Moayyed, Maryam

    2013-07-30

    A microelectromechanical (MEM) filter is disclosed which has a plurality of lattice networks formed on a substrate and electrically connected together in parallel. Each lattice network has a series resonant frequency and a shunt resonant frequency provided by one or more contour-mode resonators in the lattice network. Different types of contour-mode resonators including single input, single output resonators, differential resonators, balun resonators, and ring resonators can be used in MEM filter. The MEM filter can have a center frequency in the range of 10 MHz-10 GHz, with a filter bandwidth of up to about 1% when all of the lattice networks have the same series resonant frequency and the same shunt resonant frequency. The filter bandwidth can be increased up to about 5% by using unique series and shunt resonant frequencies for the lattice networks.

  6. Ultrastrong coupling with few (<60) electrons at 280 GHz in single LC nanogap resonators(Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Scalari, Giacomo; Keller, Janine; Cibella, Sara; Maissen, Curdin; Paravicini-Bagliani, GianLorenzo; Leoni, Roberto; Beck, Mattias; Faist, Jérôme

    2017-02-01

    Strong light-matter coupling lies at the heart of quantum optics and recently has been successfully explored also in the GHz and THz range. New, intriguing quantum optical phenomena have been predicted in the ultrastrong coupling regime, when the coupling strength Omega becomes comparable to the unperturbed frequency of the system omega_c. We recently proposed a new experimental platform where the physics of the ultrastrong coupling can be investigated at GHz-THz frequencies. We couple the inter-Landau level transition of an high-mobility 2 dimensional electron gas (2DEG) to the subwavelength photonic mode of an LC meta-atom. Our system benefits from the collective enhancement of the light-matter coupling which comes from the scaling of the coupling constant Omega with the square root of the number of electrons in the last Landau level. In our previous experiments and in literature this number varies from 10000-1000 electrons per resonator. Here we present ultrastrong coupling between a high-mobility 2DEG (mu=2.3X 10^6 cm^2/Vs) and an extremely subwavelength hybrid-LC resonator ensemble (11 resonators) with an highly reduced effective mode volume V_eff=4 x 10^-19 m^3=4 x 10^(-10) lambda^3 at a frequency of 300 GHz. The number of optically active electrons is given by the flux quantum multiplied by the effective resonator area and is proportional to the magnetic field. At the anticrossing field of B=0.73 T we measure less than 80 electrons ultrastrongly coupled to the resonator with a normalized coupling ratio Omega/omega_c=0.35. This experiment paves the way towards the study of ultrastrong coupling physics in the regime of quantum non-linearities.

  7. Mode splitting effect in FEMs with oversized Bragg resonators

    SciTech Connect

    Peskov, N. Yu.; Sergeev, A. S.; Kaminsky, A. K.; Perelstein, E. A.; Sedykh, S. N.; Kuzikov, S. V.

    2016-07-15

    Splitting of the fundamental mode in an oversized Bragg resonator with a step of the corrugation phase, which operates over the feedback loop involving the waveguide waves of different transverse structures, was found to be the result of mutual influence of the neighboring zones of the Bragg scattering. Theoretical description of this effect was developed within the framework of the advanced (four-wave) coupled-wave approach. It is shown that mode splitting reduces the selective properties, restricts the output power, and decreases the stability of the narrow-band operating regime in the free-electron maser (FEM) oscillators based on such resonators. The results of the theoretical analysis were confirmed by 3D simulations and “cold” microwave tests. Experimental data on Bragg resonators with different parameters in a 30-GHz FEM are presented. The possibility of reducing the mode splitting by profiling the corrugation parameters is shown. The use of the mode splitting effect for the output power enhancement by passive compression of the double-frequency pulse generated in the FEM with such a resonator is discussed.

  8. TlCaBaCuO high Tc superconducting microstrip ring resonators designed for 12 GHz

    NASA Technical Reports Server (NTRS)

    Subramanyam, G.; Kapoor, V. J.; Chorey, C. M.; Bhasin, K. B.

    1993-01-01

    Microwave properties of sputtered Tl-Ca-Ba-Cu-O thin films were investigated by designing, fabricating, and testing microstrip ring resonators. Ring resonators designed for 12 GHz fundamental resonance frequency, were fabricated and tested. From the unloaded Q values for the resonators, the surface resistance was calculated by separating the conductor losses from the total losses. The penetration depth was obtained from the temperature dependence of resonance frequency, assuming that the shift in resonance frequency is mainly due to the temperature dependence of penetration depth. The effective surface resistance at 12 GHz and 77 K was determined to be between 1.5 and 2.75 mOmega, almost an order lower than Cu at the same temperature and frequency. The effective penetration depth at 0 K is approximately 7000 A.

  9. Multipass modes in an open resonator

    NASA Astrophysics Data System (ADS)

    Niziev, V. G.; Grishaev, R. V.; Panchenko, V. Ya

    2015-02-01

    The papers dealing with multipass modes in open stable resonators are reviewed. A numerical model of an axially symmetric resonator is described that permits the properties of multipass modes to be studied in wave approximation. It is shown that for Fresnel numbers larger than unity, multiple reflections of radiation from the stable resonator mirrors lead to sustained quasi-stationary field oscillations in the resonator which are indicative of the essential contribution of multipass modes. The calculations in filling the resonator with the active medium have been performed for two types of lasers: with the on-axis and off-axis gain maxima. Resonator designs are suggested, trajectory selection techniques are considered to provide high-quality radiation at large Fresnel numbers. The confocal resonator properties are analyzed in the context of competition between single-pass and multipass modes. Relying on the results of calculations for multipass mode generation, a critical analysis of the experimental works is presented suggesting a logical explanation for the peculiarities which had not been physically interpreted in the original publications. An advanced understanding of the physics of multipass mode formations allowed us to put forward a special design of stable resonators for the generation of high quality radiation in high-power lasers.

  10. A quasioptical resonant-tunneling-diode oscillator operating above 200 GHz

    SciTech Connect

    Brown, E.R.; Parker, C.D.; Calawa, A.R.; Manfra, M.J.; Molvar, K.M. . Lincoln Lab.)

    1993-08-01

    A quasioptical resonant-tunneling-diode oscillator is demonstrated at frequencies above 200 GHz. The oscillator is stabilized by a semiconfocal open cavity. The maximum output power and the linewidth are approximately 50 [mu]W and 20 kHz, respectively, at a fundamental frequency of 210 GHz. By varying the cavity length, the oscillator frequency can be adjusted over a 0.4 GHz range in a repetitive manner. This behavior is explained by analogy with laser oscillators. The quasioptical RTD oscillator is well suited as a local oscillator for low-power radiometric mixers.

  11. 10 GHz fundamental mode fiber laser using a graphene saturable absorber

    NASA Astrophysics Data System (ADS)

    Martinez, Amos; Yamashita, Shinji

    2012-07-01

    All-fiber mode-locked lasers with fundamental repetition rates of several gigahertz are sought after for applications in optical communications and metrology. In this paper, we propose a fiber Fabry-Pérot laser mode-locked by a graphene-based saturable absorber that operates at a fundamental repetition rate of 9.67 GHz. We use this laser as the seed for the generation of supercontinuum with 0.08 nm mode spacing.

  12. Development of a dual mode satellite traveling wave tube 11GHz, 12W/6W

    NASA Astrophysics Data System (ADS)

    Deml, L.

    1981-02-01

    A high power 11GHz dual mode traveling wave tube (TWT) was developed for use in communication satellites. The tube is based on the technology of previous space-qualified tubes (TL12006, TL12022, and TL12025). The tube operates at 12 or 6W, separated by 3dB, without a dramatic efficiency loss in the low power mode. Gain, efficiency and nonlinear distortion criteria are all met, by channel tuning the tube within the operating band (from 10.9 to 11.8 GHz). The channel bandwidth is 100MHz.

  13. Imaging of quantized magnetostatic modes using spatially resolved ferromagnetic resonance

    NASA Astrophysics Data System (ADS)

    Tamaru, S.; Bain, J. A.; van de Veerdonk, R. J. M.; Crawford, T. M.; Covington, M.; Kryder, M. H.

    2002-05-01

    We present a measurement technique for performing spatially resolved ferromagnetic resonance and directly imaging quantized magnetostatic modes in magnetic samples that undergo high frequency magnetic drive fields (up to 8 GHz). The dynamic response of a 50×50 μm2 permalloy structure (100 nm thick) under a 7.04 GHz highly nonuniform drive field was measured as a function of the dc bias field using this technique. The magnetization variation observed indicates that quantized magnetostatic mode waves appear at certain bias fields, with the number of nodes decreasing with an increase in the bias field. We tentatively assign the indices of each mode using the Damon-Eshbach (DE) model. Similar modes have been observed for a similar sample geometry using an inductive measurement and they showed good agreement with the DE model. However, the result measured using this technique showed some discrepancy with the DE model and the spatial patterns observed are more complicated than simple one-dimensional standing waves. This complexity suggests that analysis beyond that of the DE model is required to explain the observations.

  14. Resonant mode at the band edge

    NASA Astrophysics Data System (ADS)

    Castro-Garay, P.; Vargas Hernández, D.; Manzanares-Martinez, J.; Corella-Madueño, A.; Rosas-Burgos, A.; Tanori, Dra J.; Pellat, A.; Estrada, S.

    2016-09-01

    We have found the solution of the boundary value problem for reflectance and transmittance of normal circularly polarized light impinges on a cholesteric elastomer film with a twist defect. We have found a tunable resonant mode in the reflectance band for right and left circularly polarized light. When the values of chiral twist defect are increased in the cholesteric elastomer film, the resonant modes changes to shorter wavelength until the edge band is reached.

  15. Triad mode resonant interactions in suspended cables

    NASA Astrophysics Data System (ADS)

    Guo, TieDing; Kang, HouJun; Wang, LianHua; Zhao, YueYu

    2016-03-01

    A triad mode resonance, or three-wave resonance, is typical of dynamical systems with quadratic nonlinearities. Suspended cables are found to be rich in triad mode resonant dynamics. In this paper, modulation equations for cable's triad resonance are formulated by the multiple scale method. Dynamic conservative quantities, i.e., mode energy and Manley-Rowe relations, are then constructed. Equilibrium/dynamic solutions of the modulation equations are obtained, and full investigations into their stability and bifurcation characteristics are presented. Various bifurcation behaviors are detected in cable's triad resonant responses, such as saddle-node, Hopf, pitchfork and period-doubling bifurcations. Nonlinear behaviors, like jump and saturation phenomena, are also found in cable's responses. Based upon the bifurcation analysis, two interesting properties associated with activation of cable's triad resonance are also proposed, i.e., energy barrier and directional dependence. The first gives the critical amplitude of high-frequency mode to activate cable's triad resonance, and the second characterizes the degree of difficulty for activating cable's triad resonance in two opposite directions, i.e., with positive or negative internal detuning parameter.

  16. Generating multi-mode entangled coherent W and GHZ states via optical system based fusion mechanism

    NASA Astrophysics Data System (ADS)

    Zang, Xue-Ping; Yang, Ming; Wu, Wei-Feng; Fan, Hong-Yi

    2017-05-01

    Fusion technology has been demonstrated to be a good method for generating a large-scale entangled coherent W or GHZ state from two small ones in QED system. It is of importance to study how to fuse small-scale entangled coherent W or GHZ states via optical system. In this paper, we present a scheme for generating larger entangled coherent W or GHZ state in an optical system by virtue of fusion technology. The key fusion mechanism is realized by photon detectors and a Mach-Zehnder interferometer with its two arms immersed in Kerr media, by which an n-mode entangled coherent W state and an m-mode entangled coherent W state can be probabilistically fused into an (n+m-2)-mode entangled coherent W state. This fusion scheme applies to entangled coherent GHZ state too but with a unit probability of success. Feasibility analysis indicates that our fusion scheme may be realized with current experimental technology. Large-scale entangled coherent W and GHZ states may find new applications in quantum communication.

  17. First results of the 2.45 GHz Oshima electron cyclotron resonance ion source

    SciTech Connect

    Asaji, T.; Nakamura, T.; Furuse, M.; Hitobo, T.; Uchida, T.; Muramatsu, M.; Kato, Y.

    2016-02-15

    A new electron cyclotron resonance ion source has been constructed at Oshima College with a 2.45 GHz magnetron microwave source and permanent magnets employed as the main components. In addition, a solid-state power amplifier with a frequency range of 2.5–6.0 GHz was installed to study two-frequency plasma heating. Three solenoid coils were set up for adjusting the axial magnetic fields. Argon plasma generation and ion beam production have been conducted during the first year of operation. Ion current densities in the ECR plasma were measured using a biased disk. For 2.45 and 4.65 GHz two-frequency plasma heating, the ion density was approximately 1.5 times higher than that of 2.45 GHz single-frequency heating.

  18. High Speed Laser with 100 Ghz Resonance Frequency

    DTIC Science & Technology

    2014-02-28

    practical limit occurs when the detuned master laser encounters the next-order laser modes (i.e. Fabry - Perot modes). Our current DFB slave laser...lasers and vertical- cavity surface-emitting lasers (VCSELs), showing the broad applicability of the technique and that the coupling Q (optical quality...Q-factor, and also increases as the injection power and optical frequency increase. Additionally, we show that lasers with very different cavity

  19. Temperature Sensing by Using Film Bulk Acoustic Resonator at 2.4 GHz Band

    NASA Astrophysics Data System (ADS)

    Kao, Yao-Huang; Lin, Jon-Hong

    2009-11-01

    A four-layered film bulk acoustic resonator (FBAR) with an Al/AlN/SiN/Au composite structure was fabricated. The FBAR is composed of a surface micromachined cantilever whose copper scarification layer is released by wet etching. A temperature coefficient (TC) of resonant frequency of -34.5 ppm/°C in the temperature range from 10 to 80 °C at 2.4 GHz is obtained. Using this resonator, an oscillator for temperature sensing was constructed, in which temperature can be detected easily by measuring the shift in oscillation frequency. The TC of the oscillator is almost the same as that of the resonator.

  20. Mode Profiles in Waveguide-Coupled Resonators

    NASA Technical Reports Server (NTRS)

    Hunt, William D.; Cameron, Tom; Saw, John C. B.; Kim, Yoonkee

    1993-01-01

    Surface acoustic wave (SAW) waveguide-coupled resonators are of considerable interest for narrow-band filter applications, though to date there has been very little published on the acoustic details of their operation. As in any resonator, one must fully understand its mode structure and herein we study the SAW mode profiles in these devices. Transverse mode profiles in the resonant cavity of the device were measured at various frequencies of interest using a knife-edge laser probe. In addition we predict the mode profiles for the device structure by two independent methods. One is a stack-matrix approach adapted from integrated optics and the other is a conventional analytical eigenmode analysis of the Helmholtz equation. Both modeling techniques are in good agreement with the measured results.

  1. Suppression of spurious mode oscillation in mega-watt 77-GHz gyrotron as a high quality probe beam source for the collective Thomson scattering in LHD

    SciTech Connect

    Ogasawara, S.; Kubo, S.; Nishiura, M.; Tanaka, K.; Shimozuma, T.; Yoshimura, Y.; Igami, H.; Takahashi, H.; Ito, S.; Takita, Y.; Kobayashi, S.; Mizuno, Y.; Okada, K.; Tatematsu, Y.; Saito, T.; Minami, R.; Kariya, T.; Imai, T.

    2012-10-15

    Collective Thomson scattering (CTS) diagnostic requires a strong probing beam to diagnose a bulk and fast ion distribution function in fusion plasmas. A mega-watt gyrotron for electron cyclotron resonance heating is used as a probing beam in the large helical device. Spurious mode oscillations are often observed during the turning on/off phase of the modulation. The frequency spectra of the 77-GHz gyrotron output power have been measured, and then one of the spurious modes, which interferes with the CTS receiver system, is identified as the TE{sub 17,6} mode at the frequency of 74.7 GHz. The mode competition calculation indicates that the increase of the magnetic field strength at the gyrotron resonator can avoid such a spurious mode and excite only the main TE{sub 18,6} mode. The spurious radiation at the 74.7 GHz is experimentally demonstrated to be suppressed in the stronger magnetic field than that optimized for the high-power operation.

  2. Near- infrared, mode-locked waveguide lasers with multi-GHz repetition rates

    NASA Astrophysics Data System (ADS)

    Choudhary, A.; Lagatsky, A. A.; Zhang, Z. Y.; Zhou, K. J.; Wang, Q.; Hogg, R. A.; Pradeesh, K.; Rafailov, E. U.; Resan, B.; Oehler, A. E. H.; Weingarten, K. J.; Sibbett, W.; Brown, C. T. A.; Shepherd, D. P.

    2014-02-01

    In this work, we discuss mode-locking results obtained with low-loss, ion-exchanged waveguide lasers. With Yb3+-doped phosphate glass waveguide lasers, a repetition rate of up to 15.2 GHz was achieved at a wavelength of 1047 nm with an average power of 27 mW and pulse duration of 811 fs. The gap between the waveguide and the SESAM introduced negative group velocity dispersion via the Gires Tournois Interferometer (GTI) effect which allowed the soliton mode-locking of the device. A novel quantum dot SESAM was used to mode-lock Er3+, Yb3+-doped phosphate glass waveguide lasers around 1500 nm. Picosecond pulses were achieved at a maximum repetition rate of 6.8 GHz and an average output power of 30 mW. The repetition rate was tuned by more than 1 MHz by varying the pump power.

  3. A 20 GHz, high efficiency dual mode TWT for the ACTS program

    NASA Astrophysics Data System (ADS)

    Muennemann, Frank; Dombro, Louis; Long, Jin

    The development of a 50 W/10 W dual mode K-band downlink TWT is examined, and its performance is evaluated. The designs of the electron gun, RF circuit, and collector for the TWT, which is enclosed in a capsule, are described. It is observed that the high power mode (HPM) power output is at 50 GHz and the low power mode (LPM) output is at 12 GHz; the saturated gain is 52.5 dB for HPM and 3 dB for LPM; the AM-PM is 4.2 dB; the HPM dc power output is 104 W; and the LPM dc output is 42 W; and the efficiency is 45 percent for the HPM and 28.6 percent for the LPM.

  4. Microwave Photonics Systems Based on Whispering-gallery-mode Resonators

    PubMed Central

    Coillet, Aurélien; Henriet, Rémi; Phan Huy, Kien; Jacquot, Maxime; Furfaro, Luca; Balakireva, Irina; Larger, Laurent; Chembo, Yanne K.

    2013-01-01

    Microwave photonics systems rely fundamentally on the interaction between microwave and optical signals. These systems are extremely promising for various areas of technology and applied science, such as aerospace and communication engineering, sensing, metrology, nonlinear photonics, and quantum optics. In this article, we present the principal techniques used in our lab to build microwave photonics systems based on ultra-high Q whispering gallery mode resonators. First detailed in this article is the protocol for resonator polishing, which is based on a grind-and-polish technique close to the ones used to polish optical components such as lenses or telescope mirrors. Then, a white light interferometric profilometer measures surface roughness, which is a key parameter to characterize the quality of the polishing. In order to launch light in the resonator, a tapered silica fiber with diameter in the micrometer range is used. To reach such small diameters, we adopt the "flame-brushing" technique, using simultaneously computer-controlled motors to pull the fiber apart, and a blowtorch to heat the fiber area to be tapered. The resonator and the tapered fiber are later approached to one another to visualize the resonance signal of the whispering gallery modes using a wavelength-scanning laser. By increasing the optical power in the resonator, nonlinear phenomena are triggered until the formation of a Kerr optical frequency comb is observed with a spectrum made of equidistant spectral lines. These Kerr comb spectra have exceptional characteristics that are suitable for several applications in science and technology. We consider the application related to ultra-stable microwave frequency synthesis and demonstrate the generation of a Kerr comb with GHz intermodal frequency. PMID:23963358

  5. Microwave photonics systems based on whispering-gallery-mode resonators.

    PubMed

    Coillet, Aurélien; Henriet, Rémi; Phan Huy, Kien; Jacquot, Maxime; Furfaro, Luca; Balakireva, Irina; Larger, Laurent; Chembo, Yanne K

    2013-08-05

    Microwave photonics systems rely fundamentally on the interaction between microwave and optical signals. These systems are extremely promising for various areas of technology and applied science, such as aerospace and communication engineering, sensing, metrology, nonlinear photonics, and quantum optics. In this article, we present the principal techniques used in our lab to build microwave photonics systems based on ultra-high Q whispering gallery mode resonators. First detailed in this article is the protocol for resonator polishing, which is based on a grind-and-polish technique close to the ones used to polish optical components such as lenses or telescope mirrors. Then, a white light interferometric profilometer measures surface roughness, which is a key parameter to characterize the quality of the polishing. In order to launch light in the resonator, a tapered silica fiber with diameter in the micrometer range is used. To reach such small diameters, we adopt the "flame-brushing" technique, using simultaneously computer-controlled motors to pull the fiber apart, and a blowtorch to heat the fiber area to be tapered. The resonator and the tapered fiber are later approached to one another to visualize the resonance signal of the whispering gallery modes using a wavelength-scanning laser. By increasing the optical power in the resonator, nonlinear phenomena are triggered until the formation of a Kerr optical frequency comb is observed with a spectrum made of equidistant spectral lines. These Kerr comb spectra have exceptional characteristics that are suitable for several applications in science and technology. We consider the application related to ultra-stable microwave frequency synthesis and demonstrate the generation of a Kerr comb with GHz intermodal frequency.

  6. Continuous-Wave Operation of a Frequency-Tunable 460-GHz Second-Harmonic Gyrotron for Enhanced Nuclear Magnetic Resonance

    PubMed Central

    Torrezan, Antonio C.; Han, Seong-Tae; Mastovsky, Ivan; Shapiro, Michael A.; Sirigiri, Jagadishwar R.; Temkin, Richard J.; Barnes, Alexander B.; Griffin, Robert G.

    2011-01-01

    The design, operation, and characterization of a continuous-wave (CW) tunable second-harmonic 460-GHz gyrotron are reported. The gyrotron is intended to be used as a submillimeter-wave source for 700-MHz nuclear magnetic resonance experiments with sensitivity enhanced by dynamic nuclear polarization. The gyrotron operates in the whispering-gallery mode TE11,2 and has generated 16 W of output power with a 13-kV 100-mA electron beam. The start oscillation current measured over a range of magnetic field values is in good agreement with theoretical start currents obtained from linear theory for successive high-order axial modes TE11,2,q. The minimum start current is 27 mA. Power and frequency tuning measurements as a function of the electron cyclotron frequency have also been carried out. A smooth frequency tuning range of 1 GHz was obtained for the operating second-harmonic mode either by magnetic field tuning or beam voltage tuning. Long-term CW operation was evaluated during an uninterrupted period of 48 h, where the gyrotron output power and frequency were kept stable to within ±0.7% and ±6 ppm, respectively, by a computerized control system. Proper operation of an internal quasi-optical mode converter implemented to transform the operating whispering-gallery mode to a Gaussian-like beam was also verified. Based on the images of the gyrotron output beam taken with a pyroelectric camera, the Gaussian-like mode content of the output beam was computed to be 92% with an ellipticity of 12%. PMID:21243088

  7. Continuous-Wave Operation of a Frequency-Tunable 460-GHz Second-Harmonic Gyrotron for Enhanced Nuclear Magnetic Resonance

    PubMed Central

    Torrezan, Antonio C.; Han, Seong-Tae; Mastovsky, Ivan; Shapiro, Michael A.; Sirigiri, Jagadishwar R.; Temkin, Richard J.; Griffin, Robert G.; Barnes, Alexander B.

    2012-01-01

    The design, operation, and characterization of a continuous-wave (CW) tunable second-harmonic 460-GHz gyrotron are reported. The gyrotron is intended to be used as a submillimeter-wave source for 700-MHz nuclear magnetic resonance experiments with sensitivity enhanced by dynamic nuclear polarization. The gyrotron operates in the whispering-gallery mode TE11,2 and has generated 16 W of output power with a 13-kV 100-mA electron beam. The start oscillation current measured over a range of magnetic field values is in good agreement with theoretical start currents obtained from linear theory for successive high-order axial modes TE11,2,q. The minimum start current is 27 mA. Power and frequency tuning measurements as a function of the electron cyclotron frequency have also been carried out. A smooth frequency tuning range of 1 GHz was obtained for the operating second-harmonic mode either by magnetic field tuning or beam voltage tuning. Long-term CW operation was evaluated during an uninterrupted period of 48 h, where the gyrotron output power and frequency were kept stable to within ±0.7% and ±6 ppm, respectively, by a computerized control system. Proper operation of an internal quasi-optical mode converter implemented to transform the operating whispering-gallery mode to a Gaussian-like beam was also verified. Based on the images of the gyrotron output beam taken with a pyroelectric camera, the Gaussian-like mode content of the output beam was computed to be 92% with an ellipticity of 12%. PMID:23761938

  8. 11-GHz waveguide Nd:YAG laser CW mode-locked with single-layer graphene

    PubMed Central

    Okhrimchuk, Andrey G.; Obraztsov, Petr A.

    2015-01-01

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

  9. 11-GHz waveguide Nd:YAG laser CW mode-locked with single-layer graphene.

    PubMed

    Okhrimchuk, Andrey G; Obraztsov, Petr A

    2015-06-08

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

  10. Synchronized 4 × 12 GHz hybrid harmonically mode-locked semiconductor laser based on AWG.

    PubMed

    Liu, S; Lu, D; Zhang, R; Zhao, L; Wang, W; Broeke, R; Ji, C

    2016-05-02

    We report a monolithically integrated synchronized four wavelength channel mode-locked semiconductor laser chip based on arrayed waveguide grating and fabricated in the InP material system. Device fabrication was completed in a multiproject wafer foundry run on the Joint European Platform for Photonic Integration of Components and Circuits. The integrated photonic chip demonstrated 5th harmonic electrical hybrid mode-locking operation with four 400 GHz spacing wavelength channels and synchronized to a 12.7 GHz RF clock, for nearly transform-limited optical pulse trains from a single output waveguide. A low timing jitter of 0.349 ps, and RF frequency locking range of ~50 MHz were also achieved.

  11. Mode-resolved 10-GHz frequency comb from a femtosecond optical parametric oscillator.

    PubMed

    Zhang, Zhaowei; Balskus, Karolis; McCracken, Richard A; Reid, Derryck T

    2015-06-15

    We report a 10-GHz frequency comb generated by filtering a 333.3-MHz OPO frequency comb with a Fabry-Perot (FP) cavity, which was directly stabilized to the incident fundamental comb. This result is supported by a detailed analysis of the Vernier-effect-induced multiple peaks in the transmitted comb power as the FP cavity spacing is detuned. Modes of the generated 10-GHz comb were clearly resolved by a Fourier transform spectrometer with a spectral resolution of 830 MHz, considerably better than the Nyquist sampling limit. The potentially broad tuning range of this mode-resolved OPO frequency comb opens unique opportunities for precise frequency metrology and high-precision spectroscopy.

  12. Small-signal analysis of ultra-high-speed 30 GHz VCSELs using an advanced multi-mode approach

    NASA Astrophysics Data System (ADS)

    Hamad, Wissam; Bou Sanayeh, Marwan; Hamad, Hassan; Hamad, Mustapha; Georges, Semaan; Hofmann, Werner

    2017-05-01

    Vertical-cavity surface-emitting lasers (VCSELs) have emerged as a pioneering solution for many high-speed data communication challenges. Therefore, higher bandwidth optical interconnects with data rates in the range of 100 Gbit/s require directly modulated VCSELs with ultimate speed ratings. The small-signal modulation response of a VCSEL can be isolated from the entire system, thus providing accurate information on the intrinsic laser dynamics. Until now, it is assumed that the dynamic behavior of oxide-confined multi-mode VCSELs can be fully modeled using the single-mode rate equations developed for edge-emitters, even though the deviation between the single-mode based model and the measured data is substantially large. Using an advanced theoretical approach, rate equations for multi-mode VCSELs were developed and the small-signal modulation response of ultra-high speed devices with split carrier reservoirs corresponding with the resonating modes were analyzed. Based on this theoretical work, and including gain compression in the model, the analyzed VCSELs showed modulation bandwidth around and exceeding 30 GHz. The common set of figures of merit is extended consistently to explain dynamic properties caused by the coupling of the different reservoirs. Furthermore, beside damping and relaxation oscillation frequency, the advanced model, with gain compression included, can reveal information on the photon lifetime and highlights high-speed effects such as reduced damping in VCSELs due to a negative gain compression factor.

  13. Mode Orientation Control For Sapphire Dielectric Ring Resonator

    NASA Technical Reports Server (NTRS)

    Santiago, David G.; Dick, G. John; Prata, Aluizio

    1996-01-01

    Small sapphire tuning wedge used in technique for solving mode-purity problem associated with sapphire dielectric-ring resonator part of cryogenic microwave frequency discriminator. Breaks quasi-degeneracy of two modes and allows selective coupling to just one mode. Wedge mounted on axle entering resonator cavity and rotated while resonator cryogenically operating in vacuum. Furthermore, axle moved vertically to tune resonant frequency.

  14. An automated 60 GHz open resonator system for precision dielectric measurement

    NASA Astrophysics Data System (ADS)

    Afsar, Mohammed N.; Li, Xiaohui; Chi, Hua

    1990-12-01

    An automated open resonator system was designed and constructed for precision measurement of the loss tangent and dielectric permittivity of low absorbing materials at 60 GHz. The use of a high-Q hemispherical Fabry-Perot cavity together with highly stabilized synthesized phase-locked Gunn oscillator sources and a superheterodyne receiver made it possible to measure loss tangent values as low as 10 microrad. Both cavity length variation and frequency variation techniques were utilized to provide precise data.

  15. Optimized TE01-to-TM11 mode conversion in highly overmoded circular waveguide at 70 and 140 GHz

    NASA Astrophysics Data System (ADS)

    Sturm, H.

    1985-06-01

    Mode coupling in bent, oversized, smoothly walled circular waveguides was studied by numerical integration of coupled-mode equations, to optimize high power TE01-to-TM11 mode transducers at 70 and 140 GHZ. Such transducers are used in the mode conversion sequence TE on to TE01 to TM11 to HE11 to generate the linearly polarized HE11 (Gaussianlike) mode from the circular electric TE on gyrotron mode. The balanced HE11 hydrid mode is ideal for electron cyclotron plasma heating in thermonuclear fusion research and for other technical applications. The lowest level of unwanted spurious modes is achieved with sinusoidal curvature distribution instead of constant curvature. The calculated efficiencies of 98.0% at 70 GHZ and 95.2% at 140 GHZ (inner diameter 27.79 mm, ohmic attenuation included) are in excellent agreement with the measured values (97.6% and 95%) respectively.

  16. High frequency electron nuclear double resonance at 239 GHz using a far-infrared laser source

    SciTech Connect

    Paschedag, L.; van Tol, J.; Wyder, P.

    1995-10-01

    We report on the application of {sup 14}N electron nuclear double resonance (ENDOR) at 8.5 T and 239 GHz ({lambda}=1.2 mm) in a {gamma}-irradiated betaine arsenate single crystal. A laser was used as a far-infrared radiation source in a transmission-type electron paramagnetic resonance (EPR) setup without a cavity. The four expected nitrogen ENDOR lines were observed, but due to insufficient saturation of the EPR transitions the signal/noise ratio was not larger than 10 and the signals vanished at temperatures above 20 K. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  17. Mode-hop-free tuning over 135 GHz of external cavity diode lasers without antireflection coating

    NASA Astrophysics Data System (ADS)

    Dutta, S.; Elliott, D. S.; Chen, Y. P.

    2012-03-01

    We report an external cavity diode laser (ECDL), using a diode whose front facet is not anti-reflection (AR) coated that has a mode-hop-free (MHF) tuning range greater than 135 GHz. We achieved this using a short external cavity and by simultaneously tuning the internal and external modes of the laser. We find that the precise location of the pivot point of the grating in our laser is less critical than commonly believed. The general applicability of the method, combined with the compact portable mechanical and electronic design, makes it well suited for both research and industrial applications.

  18. Cascaded Brillouin lasing in monolithic barium fluoride whispering gallery mode resonators

    SciTech Connect

    Lin, Guoping Diallo, Souleymane; Saleh, Khaldoun; Martinenghi, Romain; Beugnot, Jean-Charles; Sylvestre, Thibaut; Chembo, Yanne K.

    2014-12-08

    We report the observation of stimulated Brillouin scattering and lasing at 1550 nm in barium fluoride (BaF{sub 2}) crystal. Brillouin lasing was achieved with ultra-high quality (Q) factor monolithic whispering gallery mode mm-size disk resonators. Overmoded resonators were specifically used to provide cavity resonances for both the pump and all Brillouin Stokes waves. Single and multiple Brillouin Stokes radiations with frequency shift ranging from 8.2 GHz up to 49 GHz have been generated through cascaded Brillouin lasing. BaF{sub 2} resonator-based Brillouin lasing can find potential applications for high-coherence lasers and microwave photonics.

  19. 175 GHz, 400-fs-pulse harmonically mode-locked surface emitting semiconductor laser.

    PubMed

    Wilcox, Keith G; Quarterman, Adrian H; Apostolopoulos, Vasilis; Beere, Harvey E; Farrer, Ian; Ritchie, David A; Tropper, Anne C

    2012-03-26

    We report a harmonically mode-locked vertical external cavity surface emitting laser (VECSEL) producing 400 fs pulses at a repetition frequency of 175 GHz with an average output power of 300 mW. Harmonic mode-locking was established using a 300 µm thick intracavity single crystal diamond heat spreader in thermal contact with the front surface of the gain sample using liquid capillary bonding. The repetition frequency was set by the diamond microcavity and stable harmonic mode locking was achieved when the laser cavity length was tuned so that the laser operated on the 117th harmonic of the fundamental cavity. When an etalon placed intracavity next to the gain sample, but not in thermal contact was used pulse groups were observed. These contained 300 fs pulses with a spacing of 5.9 ps. We conclude that to achieve stable harmonic mode locking at repetition frequencies in the 100s of GHz range in a VECSEL there is a threshold pulse energy above which harmonic mode locking is achieved and below which groups of pulses are observed.

  20. Status report of the 28 GHz superconducting electron cyclotron resonance ion source VENUS (invited)

    SciTech Connect

    Leitner, D.; Lyneis, C.M.; Loew, T.; Todd, D.S.; Virostek, S.; Tarvainen, O.

    2006-03-15

    The superconducting versatile electron cyclotron resonance (ECR) ion source for nuclear science (VENUS) is a next generation superconducting ECR ion source designed to produce high-current, high-charge-state ions for the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory. VENUS also serves as the prototype ion source for the rare isotope accelerator (RIA) front end, where the goal is to produce intense beams of medium-charge-state ions. Example beams for the RIA accelerator are 15 p {mu}A of Kr{sup 17+}(260 e {mu}A), 12 p {mu}A of Xe{sup 20+} (240 e {mu}A of Xe{sup 20+}), and 8 p {mu}A of U{sup 28+}(230 e {mu}A). To achieve these high currents, VENUS has been optimized for operation at 28 GHz, reaching maximal confinement fields of 4 and 3 T axially and over 2.2 T on the plasma chamber wall radially. After a commissioning phase at 18 GHz, the source started the 28 GHz operation in the summer of 2004. During that ongoing 28 GHz commissioning process, record ion-beam intensities have been extracted. For instance, measured extracted currents for the low to medium charge states were 270 e {mu}A of Xe{sup 27+} and 245 e {mu}A of Bi{sup 29+}, while for the higher charge states 15 e {mu}A of Xe{sup 34+}, 15 e {mu}A of Bi{sup 41+}, and 0.5 e {mu}A of Bi{sup 50+} could be produced. Results from the ongoing 28 GHz commissioning as well as results using double-frequency heating with 18 and 28 GHz for oxygen and xenon are presented. The effect of the minimum B field on the ion source performance has been systematically measured for 18 and 28 GHz. In both cases the performance peaked at a minimum B field of about 80% of the resonance field. In addition, a strong dependence of the x-ray flux and energy on the minimum B field value was found.

  1. A mode converter to generate a Gaussian-like mode for injection into the VENUS electron cyclotron resonance ion source

    SciTech Connect

    Lyneis, C. Benitez, J.; Hodgkinson, A.; Strohmeier, M.; Todd, D.; Plaum, B.; Thuillier, T.

    2014-02-15

    A number of superconducting electron cyclotron resonance (ECR) ion sources use gyrotrons at either 24 or 28 GHz for ECR heating. In these systems, the microwave power is launched into the plasma using the TE{sub 01} circular waveguide mode. This is fundamentally different and may be less efficient than the typical rectangular, linearly polarized TE{sub 10} mode used for launching waves at lower frequencies. To improve the 28 GHz microwave coupling in VENUS, a TE{sub 01}-HE{sub 11} mode conversion system has been built to test launching HE{sub 11} microwave power into the plasma chamber. The HE{sub 11} mode is a quasi-Gaussian, linearly polarized mode, which should couple strongly to the plasma electrons. The mode conversion is done in two steps. First, a 0.66 m long “snake” converts the TE{sub 01} mode to the TE{sub 11} mode. Second, a corrugated circular waveguide excites the HE{sub 11} mode, which is launched directly into the plasma chamber. The design concept draws on the development of similar devices used in tokamaks and stellerators. The first tests of the new coupling system are described below.

  2. Ferromagnetic resonance and resonance modes in kagome lattices: From an open to a closed kagome structure

    NASA Astrophysics Data System (ADS)

    Dubowik, J.; Kuświk, P.; Matczak, M.; Bednarski, W.; Stobiecki, F.; Aleshkevych, P.; Szymczak, H.; Kisielewski, M.; Kisielewski, J.

    2016-06-01

    We present ferromagnetic resonance (FMR) investigations of 20 nm thick permalloy (Ni80Fe20 ) elements (width W =200 nm, length L =470 nm, period a =500 nm) arranged in open and closed artificial kagome lattices. The measurements were done at 9.4 and 34 GHz to ensure a saturated or near-saturated magnetic state of the kagome structures. The FMR data are analyzed in the framework of an analytical macrospin model which grasps the essential features of the bulk and edge modes at these microwave frequencies and is in agreement with the results of micromagnetic simulations. Polar plots of the resonance fields versus the field angle made by the direction of the magnetic field with respect to the main symmetry directions of the kagome lattice are compared with the results of the analytical model. The measured FMR spectra with a sixfold rotational symmetry qualitatively reproduce the structure expected from the theory. Magnetic dipolar interactions between the elements of the kagome lattices result in the mixing of edge and bulklike excitations at 9.4 GHz and in a systematic deviation from the model, especially for the closed kagome lattice.

  3. Optimization Of Shear Modes To Produce Enhanced Bandwidth In Ghz GaP Bragg Cells

    NASA Astrophysics Data System (ADS)

    Soos, J., I.; Rosemeier, R. G.; Rosenbaum, J.

    1988-02-01

    Applications of Gallium Phosphide (GaP) acousto-optic devices, at wavelengths from 570nm - 1.06um seem to be ideal for fiber optic modulators, scanners, deflectors, frequency shifters, Q-switches and mode lockers. One of the major applications are for RF spectrometers in early warning radar receivers and auto-correlators. Longitudinal GaP acousto-optic Bragg cells which have respectively operational frequencies in the range of 200 MHz - 3 GHz and diffraction efficiencies in the range of 120%/RF watt to 1%/RF watt have recently been fabricated. Comparatively, shear GaP devices which have operational frequencies in the range of 200 MHz to 2 GHz and diffraction efficiencies from 80%/RF watt to 7%/RF watt have also been constructed.

  4. Electric field tunable 60 GHz ferromagnetic resonance response in barium ferrite-barium strontium titanate multiferroic heterostructures

    NASA Astrophysics Data System (ADS)

    Song, Young-Yeal; Das, Jaydip; Krivosik, Pavol; Mo, Nan; Patton, Carl E.

    2009-05-01

    A magnetic-ferroelectric film heterostructure with a large electric field tuning of the ferromagnetic resonance (FMR) mode was fabricated. Pulse laser deposited 30 nm thick Pt electrodes and 3 μm thick barium strontium titanate films on Nb-doped strontium titanate substrates were capped with an unbonded 200 μm thick single crystal in-plane c-axis barium hexaferrite slab. The structure gives a 60 GHz FMR frequency shift of 16 MHz at a bias of 29 V, for an average response of 0.55 MHz/V. The maximum incremental tuning response at 29 V was 1.3 MHz/V. This is a hundredfold improvement over previous results.

  5. Aptasensors Based on Whispering Gallery Mode Resonators.

    PubMed

    Nunzi Conti, Gualtiero; Berneschi, Simome; Soria, Silvia

    2016-07-16

    In this paper, we review the literature on optical evanescent field sensing in resonant cavities where aptamers are used as biochemical receptors. The combined advantages of highly sensitive whispering gallery mode resonator (WGMR)-based transducers, and of the unique properties of aptamers make this approach extremely interesting in the medical field, where there is a particularly high need for devices able to provide real time diagnosis for cancer, infectious diseases, or strokes. However, despite the superior performances of aptamers compared to antibodies and WGMR to other evanescent sensors, there is not much literature combining both types of receptors and transducers. Up to now, the WGMR that have been used are silica microspheres and silicon oxynitride (SiON) ring resonators.

  6. Aptasensors Based on Whispering Gallery Mode Resonators

    PubMed Central

    Nunzi Conti, Gualtiero; Berneschi, Simome; Soria, Silvia

    2016-01-01

    In this paper, we review the literature on optical evanescent field sensing in resonant cavities where aptamers are used as biochemical receptors. The combined advantages of highly sensitive whispering gallery mode resonator (WGMR)-based transducers, and of the unique properties of aptamers make this approach extremely interesting in the medical field, where there is a particularly high need for devices able to provide real time diagnosis for cancer, infectious diseases, or strokes. However, despite the superior performances of aptamers compared to antibodies and WGMR to other evanescent sensors, there is not much literature combining both types of receptors and transducers. Up to now, the WGMR that have been used are silica microspheres and silicon oxynitride (SiON) ring resonators. PMID:27438861

  7. Engineering optical mode ferromagnetic resonance in FeCoB films with ultrathin Ru insertion

    PubMed Central

    Li, Shandong; Wang, Cuiling; Chu, Xian-Ming; Miao, Guo-Xing; Xue, Qian; Zou, Wenqin; Liu, Meimei; Xu, Jie; Li, Qiang; Dai, Youyong; Yan, Shishen; Kang, Shishou; Long, Yunze; Lü, Yueguang

    2016-01-01

    Ferromagnetic resonance (FMR) in soft magnetic films (SMFs) to a large extent determines the maximum working frequency of magnetic devices. The FMR frequency (fr) in an optical mode is usually much higher than that in the corresponding acoustic mode for exchange coupled ferromagnet/nonmagnet/ferromagnet (FM/NM/FM) trilayers. In this study, we prepared a 50 nm FeCoB film with uniaxial magnetic anisotropy (UMA), showing a high acoustic mode fr of 4.17 GHz. When an ultrathin Ru spacer was inserted in the very middle of the UMA-FeCoB film, the zero-field FMR was abruptly switched from an acoustic mode to an optical one with fr dramatically enhanced from 4.17 GHz to 11.32 GHz. Furthermore, the FMR mode can be readily tuned to optical mode only, acoustic mode only, or double mode by simply varying the applied filed, which provides a flexible way to design multi-band microwave devices. PMID:27628089

  8. Mode Q factor and lasing spectrum controls for deformed square resonator microlasers with circular sides

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

    Stable dual-mode lasing semiconductor lasers can be used as a seed source for photonic generation of optical frequency comb and terahertz carrier. Normal square resonator microlasers can support dual-mode lasing with frequency interval up to 100 GHz. Here we demonstrate ultrahigh Q deformed square resonators with the flat sides replaced by circular sides for further increasing transverse mode intervals. The stable condition of dual-mode lasing is verified based on nonlinear gain analysis. Furthermore, the beating signals of 0.43, 0.31, and 0.16 THz are obtained by the autocorrelation measurement, which indicate the deformed microlasers as an architecture for THz radiation generation. The deformed square resonators pave the way for controlling the lasing spectrum and serve as ultrahigh Q microresonators for photonic integrated circuits.

  9. A Compact 5.5 GHz Band-Rejected UWB Antenna Using Complementary Split Ring Resonators

    PubMed Central

    Islam, M. M.; Faruque, M. R. I.; Islam, M. T.

    2014-01-01

    A band-removal property employing microwave frequencies using complementary split ring resonators (CSRRs) is applied to design a compact UWB antenna wishing for the rejection of some frequency band, which is meanwhile exercised by the existing wireless applications. The reported antenna comprises optimization of a circular radiating patch, in which slotted complementary SRRs are implanted. It is printed on low dielectric FR4 substrate material fed by a partial ground plane and a microstrip line. Validated results exhibit that the reported antenna shows a wide bandwidth covering from 3.45 to more than 12 GHz, with a compact dimension of 22 × 26 mm2, and VSWR < 2, observing band elimination of 5.5 GHz WLAN band. PMID:24971379

  10. A compact 5.5 GHz band-rejected UWB antenna using complementary split ring resonators.

    PubMed

    Islam, M M; Faruque, M R I; Islam, M T

    2014-01-01

    A band-removal property employing microwave frequencies using complementary split ring resonators (CSRRs) is applied to design a compact UWB antenna wishing for the rejection of some frequency band, which is meanwhile exercised by the existing wireless applications. The reported antenna comprises optimization of a circular radiating patch, in which slotted complementary SRRs are implanted. It is printed on low dielectric FR4 substrate material fed by a partial ground plane and a microstrip line. Validated results exhibit that the reported antenna shows a wide bandwidth covering from 3.45 to more than 12 GHz, with a compact dimension of 22 × 26 mm(2), and VSWR < 2, observing band elimination of 5.5 GHz WLAN band.

  11. 14 GHz longitudinally detected electron spin resonance using microHall sensors

    NASA Astrophysics Data System (ADS)

    Bouterfas, M.; Mouaziz, S.; Popovic, R. S.

    2017-09-01

    In this work we developed a home-made LOngitudinally Detected Electron Spin Resonance (LODESR) spectrometer based on a microsize Hall sensor. A coplanar waveguide (CPW)-resonator is used to induce microwave-excitation on the sample at 14 GHz. We used InSb cross-shaped Hall devices with active areas of (10 μm × 10 μm) and (5 μm × 5 μm) . Signal intensities of the longitudinal magnetization component of DPPH and YIG samples of volumes about (10 μm) 3 and (5 μm) 3 , are measured under amplitude and frequency modulated microwave magnetic field generated by the CPW-resonator. At room temperature, 109spins /G √Hz sensitivity is achieved for 0.2mT linewidth, a result which is still better than most of inductive detected LODESR sensitivities.

  12. 2.4 GHz CMOS Power Amplifier with Mode-Locking Structure to Enhance Gain

    PubMed Central

    2014-01-01

    We propose a mode-locking method optimized for the cascode structure of an RF CMOS power amplifier. To maximize the advantage of the typical mode-locking method in the cascode structure, the input of the cross-coupled transistor is modified from that of a typical mode-locking structure. To prove the feasibility of the proposed structure, we designed a 2.4 GHz CMOS power amplifier with a 0.18 μm RFCMOS process for polar transmitter applications. The measured power added efficiency is 34.9%, while the saturated output power is 23.32 dBm. The designed chip size is 1.4 × 0.6 mm2. PMID:25045755

  13. Detecting light in whispering-gallery-mode resonators

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy (Inventor); Maleki, Lutfollah (Inventor); Mohageg, Makan (Inventor); Le, Thanh M. (Inventor)

    2012-01-01

    An optical device including a whispering gallery mode (WGM) optical resonator configured to support one or more whispering gallery modes; and a photodetector optically coupled to an exterior surface of the optical resonator to receive evanescent light from the optical resonator to detect light inside the optical resonator.

  14. 60-GHz Millimeter-wave Over Fiber with Directly Modulated Dual-mode Laser Diode

    NASA Astrophysics Data System (ADS)

    Tsai, Cheng-Ting; Lin, Chi-Hsiang; Lin, Chun-Ting; Chi, Yu-Chieh; Lin, Gong-Ru

    2016-06-01

    A directly modulated dual-mode laser diode (DMLD) with third-order intermodulation distortion (IMD3) suppression is proposed for a 60-GHz millimeter-wave over fiber (MMWoF) architecture, enabling new fiber-wireless communication access to cover 4-km single-mode-fiber (SMF) and 3-m wireless 16-QAM OFDM transmissions. By dual-mode injection-locking, the throughput degradation of the DMLD is mitigated with saturation effect to reduce its threshold, IMD3 power and relative intensity noise to 7.7 mA, -85 dBm and -110.4 dBc/Hz, respectively, providing huge spurious-free dynamic range of 85.8 dB/Hz2/3. This operation suppresses the noise floor of the DMLD carried QPSK-OFDM spectrum by 5 dB. The optical receiving power is optimized to restrict the power fading effect for improving the bit error rate to 1.9 × 10-3 and the receiving power penalty to 1.1 dB. Such DMLD based hybrid architecture for 60-GHz MMW fiber-wireless access can directly cover the current optical and wireless networks for next-generation indoor and short-reach mobile communications.

  15. 60-GHz Millimeter-wave Over Fiber with Directly Modulated Dual-mode Laser Diode

    PubMed Central

    Tsai, Cheng-Ting; Lin, Chi-Hsiang; Lin, Chun-Ting; Chi, Yu-Chieh; Lin, Gong-Ru

    2016-01-01

    A directly modulated dual-mode laser diode (DMLD) with third-order intermodulation distortion (IMD3) suppression is proposed for a 60-GHz millimeter-wave over fiber (MMWoF) architecture, enabling new fiber-wireless communication access to cover 4-km single-mode-fiber (SMF) and 3-m wireless 16-QAM OFDM transmissions. By dual-mode injection-locking, the throughput degradation of the DMLD is mitigated with saturation effect to reduce its threshold, IMD3 power and relative intensity noise to 7.7 mA, −85 dBm and −110.4 dBc/Hz, respectively, providing huge spurious-free dynamic range of 85.8 dB/Hz2/3. This operation suppresses the noise floor of the DMLD carried QPSK-OFDM spectrum by 5 dB. The optical receiving power is optimized to restrict the power fading effect for improving the bit error rate to 1.9 × 10−3 and the receiving power penalty to 1.1 dB. Such DMLD based hybrid architecture for 60-GHz MMW fiber-wireless access can directly cover the current optical and wireless networks for next-generation indoor and short-reach mobile communications. PMID:27297267

  16. 60-GHz Millimeter-wave Over Fiber with Directly Modulated Dual-mode Laser Diode.

    PubMed

    Tsai, Cheng-Ting; Lin, Chi-Hsiang; Lin, Chun-Ting; Chi, Yu-Chieh; Lin, Gong-Ru

    2016-06-14

    A directly modulated dual-mode laser diode (DMLD) with third-order intermodulation distortion (IMD3) suppression is proposed for a 60-GHz millimeter-wave over fiber (MMWoF) architecture, enabling new fiber-wireless communication access to cover 4-km single-mode-fiber (SMF) and 3-m wireless 16-QAM OFDM transmissions. By dual-mode injection-locking, the throughput degradation of the DMLD is mitigated with saturation effect to reduce its threshold, IMD3 power and relative intensity noise to 7.7 mA, -85 dBm and -110.4 dBc/Hz, respectively, providing huge spurious-free dynamic range of 85.8 dB/Hz(2/3). This operation suppresses the noise floor of the DMLD carried QPSK-OFDM spectrum by 5 dB. The optical receiving power is optimized to restrict the power fading effect for improving the bit error rate to 1.9 × 10(-3 )and the receiving power penalty to 1.1 dB. Such DMLD based hybrid architecture for 60-GHz MMW fiber-wireless access can directly cover the current optical and wireless networks for next-generation indoor and short-reach mobile communications.

  17. Fast Particle Resonant Modes on MST*

    NASA Astrophysics Data System (ADS)

    Koliner, J. J.; Forest, C. B.; Sarff, J. S.; Anderson, J. K.; Lin, L.; Ding, W. X.; Brower, D. L.; Spong, D. A.

    2011-10-01

    The interaction between fast particles and Alfvén eigenmodes (AE's) is an important process critical to magnetically confined fusion plasmas. An effort is in progress to understand AE's through theory and experiment on MST, a reversed-field pinch. Coupling of energetic particle dynamics to one or more continuum modes can introduce undamped AE's. This coupling can drive modes unstable, a condition pertinent to NBI on MST and fusion alpha particles in future RFP devices. Computational studies for MST have predicted toroidal AE's with frequencies in the 200-300 kHz range and global structure. Alfvén-wave-frequency modes have been observed with up to 1 MW of NBI. Toroidal and poloidal arrays of magnetic loops are utilized to find edge amplitudes, frequencies and mode numbers. Frequencies are in the 60-150 kHz range with n=4 and n=5, m=1. The strongest coherent activity scales inversely with density, as expected for AE's, but does not scale with magnetic field strength. Additional experiments to investigate resonance conditions and beam energy scaling have been performed. An FIR interferometer-polarimeter has been used to find internal structure of the detected modes through correlation analysis. *Supported by USDoE and NSF.

  18. Development of an 18 GHz superconducting electron cyclotron resonance ion source at RCNP.

    PubMed

    Yorita, Tetsuhiko; Hatanaka, Kichiji; Fukuda, Mitsuhiro; Kibayashi, Mitsuru; Morinobu, Shunpei; Okamura, Hiroyuki; Tamii, Atsushi

    2008-02-01

    An 18 GHz superconducting electron cyclotron resonance ion source has recently been developed and installed in order to extend the variety and the intensity of ions at the RCNP coupled cyclotron facility. Production of several ions such as O, N, Ar, Kr, etc., is now under development and some of them have already been used for user experiments. For example, highly charged heavy ion beams like (86)Kr(21+,23+) and intense (16)O(5+,6+) and (15)N(6+) ion beams have been provided for experiments. The metal ion from volatile compounds method for boron ions has been developed as well.

  19. A broadband ferromagnetic resonance spectrometer to measure thin films up to 70 GHz.

    PubMed

    Harward, I; O'Keevan, T; Hutchison, A; Zagorodnii, V; Celinski, Z

    2011-09-01

    We report the development of a broadband ferromagnetic resonance (FMR) system operating in the frequency range from 10 MHz to 70 GHz using a closed-cycle He refrigeration system for measurements of thin films and micron/nano structures. The system is capable of carrying out measurements in frequency and field domain. Using two coplanar waveguides, it is capable of simultaneously measuring two samples in the out of plane and in plane FMR geometries. The system operates in the temperature range of 27-350 K and is sensitive to less than one atomic monolayer of a single crystal Fe film.

  20. 30 GHz ultracompact electroabsorption modulator integrated with 980 nm VCSEL with resonance effect in coupled cavities

    NASA Astrophysics Data System (ADS)

    Dalir, Hamed; Koyama, Fumio

    2014-11-01

    We demonstrate an ultracompact (15-µm-long) electroabsorption slow-light modulator laterally integrated with a 980 nm VCSEL. The total device length is as small as 25 µm. A 3 dB small signal modulation bandwidth of over 30 GHz is obtained owing to the resonance effect in the coupled cavities. This bandwidth is far beyond the relaxation oscillation frequency of directly modulated VCSELs. Static extinction ratios of 4 and 8 dB are obtained at reverse bias voltages of 0.5 and 1.3 V for a 15-µm-long modulator, respectively.

  1. Micropillar Resonators for Optomechanics in the Extremely High 19-95-GHz Frequency Range

    NASA Astrophysics Data System (ADS)

    Anguiano, S.; Bruchhausen, A. E.; Jusserand, B.; Favero, I.; Lamberti, F. R.; Lanco, L.; Sagnes, I.; Lemaître, A.; Lanzillotti-Kimura, N. D.; Senellart, P.; Fainstein, A.

    2017-06-01

    Strong confinement, in all dimensions, and high mechanical frequencies are highly desirable for quantum optomechanical applications. We show that GaAs/AlAs micropillar cavities fully confine not only photons but also extremely high frequency (19-95 GHz) acoustic phonons. A strong increase of the optomechanical coupling upon reducing the pillar size is observed, together with record room-temperature Q -frequency products of 1 014. These mechanical resonators can integrate quantum emitters or polariton condensates, opening exciting perspectives at the interface with nonlinear and quantum optics.

  2. Free-Electron Laser as a Driver for a Resonant Cavity at 35 GHz

    NASA Astrophysics Data System (ADS)

    Lefevre, T.; Gardelle, J.; Rullier, J. L.; Vermare, C.; Donohue, J. T.; Meurdesoif, Y.; Lidia, S. M.

    2000-02-01

    An intense beam of relativistic electrons (800 A, 6.7 MeV) has been bunched at 35 GHz by a free-electron laser, in which output power levels exceeding 100 MW were obtained. The beam was then extracted and transported through a resonant cavity, which was excited by its passage. Microwave power levels of 10 MW were extracted from the cavity, in reasonable agreement with the simple formula which relates power to known properties of both the beam and the cavity.

  3. Free-electron laser as a driver for a resonant cavity at 35 GHz

    PubMed

    Lefevre; Gardelle; Rullier; Vermare; Donohue; Meurdesoif; Lidia

    2000-02-07

    An intense beam of relativistic electrons (800 A, 6.7 MeV) has been bunched at 35 GHz by a free-electron laser, in which output power levels exceeding 100 MW were obtained. The beam was then extracted and transported through a resonant cavity, which was excited by its passage. Microwave power levels of 10 MW were extracted from the cavity, in reasonable agreement with the simple formula which relates power to known properties of both the beam and the cavity.

  4. Review on high current 2.45 GHz electron cyclotron resonance sources (invited)

    SciTech Connect

    Gammino, S.; Celona, L.; Ciavola, G.; Maimone, F.; Mascali, D.

    2010-02-15

    The suitable source for the production of intense beams for high power accelerators must obey to the request of high brightness, stability, and reliability. The 2.45 GHz off-resonance microwave discharge sources are the ideal device to generate the requested beams, as they produce multimilliampere beams of protons, deuterons, and monocharged ions, remaining stable for several weeks without maintenance. A description of different technical designs will be given, analyzing their strength, and weakness, with regard to the extraction system and low energy beam transport line, as the presence of beam halo is detrimental for the accelerator.

  5. The third generation superconducting 28 GHz electron cyclotron resonance ion source VENUS (invited)

    SciTech Connect

    Lyneis, C.; Leitner, D.; Leitner, M.; Taylor, C.; Abbott, S.

    2010-02-15

    VENUS is a third generation electron cyclotron resonance (ECR) ion source, which incorporates a high field superconducting NbTi magnet structure, a 28 GHz gryotron microwave source and a state of the art closed cycle cryosystem. During the decade from initial concept to regular operation, it has demonstrated both the feasibility and the performance levels of this new generation of ECR ion sources and required innovation on magnet construction, plasma chamber design, and beam transport. In this paper, the development, performance, and major innovations are described as well as a look to the potential to construct a fourth generation ECR ion source.

  6. Low-frequency quadrature mode birdcage resonator.

    PubMed

    Borsboom, H M; Claasen-Vujcić, T; Gaykema, H J; Mehlkopf, T

    1997-03-01

    The birdcage resonator is frequently used in conventional MRI because of its excellent attributes. Its use in low-field MRI is restricted to field strengths higher than, for example, 0.1 T, dependent on the size of the coil. This is because of the intrinsically low inductance value of the birdcage coils. Furthermore, the sensitivity of the birdcage at low field strengths is significantly lower when compared to, for example, the solenoid. Both problems can be overcome with the multiturn technique and a novel wound birdcage coil. The quadrature mode wound birdcage coil presented in this paper can be used at frequencies as low as 100 kHz. Its sensitivity is also increased when compared to the conventional strip-ring birdcage. Homogeneity, effective volume, and methods to increase the resonator bandwidth to match the signal bandwidth are left intact. The latter is a typical low-field problem.

  7. Searching for inflationary B modes: can dust emission properties be extrapolated from 350 GHz to 150 GHz?

    NASA Astrophysics Data System (ADS)

    Tassis, Konstantinos; Pavlidou, Vasiliki

    2015-07-01

    Recent Planck results have shown that radiation from the cosmic microwave background passes through foregrounds in which aligned dust grains produce polarized dust emission, even in regions of the sky with the lowest level of dust emission. One of the most commonly used ways to remove the dust foreground is to extrapolate the polarized dust emission signal from frequencies where it dominates (e.g. ˜350 GHz) to frequencies commonly targeted by cosmic microwave background experiments (e.g. ˜150 GHz). In this Letter, we describe an interstellar medium effect that can lead to decorrelation of the dust emission polarization pattern between different frequencies due to multiple contributions along the line of sight. Using a simple 2-cloud model we show that there are two conditions under which this decorrelation can be large: (a) the ratio of polarized intensities between the two clouds changes between the two frequencies; (b) the magnetic fields between the two clouds contributing along a line of sight are significantly misaligned. In such cases, the 350 GHz polarized sky map is not predictive of that at 150 GHz. We propose a possible correction for this effect, using information from optopolarimetric surveys of dichroicly absorbed starlight.

  8. Dynamic conversion of optical modes in magnetic garnet films induced by resonances of periodic stripe domains

    NASA Astrophysics Data System (ADS)

    Winkler, H. P.; Doetsch, H.; Luehrmann, B.; Sure, S.

    1994-09-01

    Magnetic garnet films of composition (Y,Bi)3(Fe,Al)5O12 are grown by liquid phase epitaxy on (111) oriented substrates of Gd3Ga5O12. They support periodic lattices of parallel stripe domains. A simple strip antenna is used to excite the domain wall resonance and the two branches of the domain resonance in the frequency range up to 5 GHz. The resonance frequencies and the dynamic components of the magnetization are calculated using a hybridization model. Good agreement between calculated and measured resonance frequencies is obtained if the quality factor of the film is larger than 0.6. Optical modes are coupled into the waveguiding film. The excited domain resonances cause dynamic conversion of transverse electric and transverse magnetic modes by the Faraday and the Cotton-Mouton effects. Mode coupling and conversion are calculated by the perturbation theory. The dynamic conversion efficiencies are measured at the fundamental and the first harmonic frequency and at zero diffraction order as a function of the static induction applied in the film plane parallel to the stripes. Conversion efficiencies up to 18% are achieved at a frequency of 2.8 GHz. From the experimental data the precession angles are derived.

  9. Optical 40 GHz pulse source module based on a monolithically integrated mode locked DBR laser

    NASA Astrophysics Data System (ADS)

    Huettl, B.; Kaiser, R.; Kroh, M.; Schubert, C.; Jacumeit, G.; Heidrich, H.

    2005-11-01

    In this paper the performance characteristics of compact optical 40 GHz pulse laser modules consisting of a monolithic mode-locked MQW DBR laser on GaInAsP/InP are reported. The monolithic devices were fabricated as tunable multi-section buried heterostructure lasers. A DBR grating is integrated at the output port of an extended cavity in order to meet the standardized ITU wavelength channels allocated in the spectral window around 1.55 μm in optical high speed communication networks. The fabricated 40 GHz lasers modules not only emit short optical pulses (< 1.5 ps) with very low amplitude noise (<1.5 %) and phase noise levels (timing jitter: 50 fs) but also enable good pulse-to-pulse phase and long-term stability. A wavelength tuning range of 6 nm is possible and large locking bandwidths between 100 ... 260 MHz are observed. All data have been achieved by operating the lasers in a hybrid mode-locking scheme with a required minimum micro-wave power of only 12 dBm for pulse synchronization. Details on laser chip architecture and module performance are summarized and the results of a stable and error free module performance in first 160 Gb/s (4 x 40 Gb/s OTDM) RZ-DPSK transmission experiments are presented.

  10. Testing of an Advanced Internal Mode Converter for a 1.5 MW, 110 GHz Gyrotron

    NASA Astrophysics Data System (ADS)

    Tax, D. S.; Mastovsky, I.; Neilson, J.; Shapiro, M. A.; Sirigiri, J. R.; Temkin, R. J.; Torrezan, A. C.

    2009-11-01

    Megawatt gyrotrons are under development for the electron cyclotron heating (ECH) of plasmas, including ITER. To optimize the efficiency of gyrotrons and of the transmission lines, the internal mode converter (IMC) should output a perfect Gaussian beam. The TE22,6 110 GHz IMC we have implemented consists of a helically-cut launcher and three smooth curved mirrors. The theoretically predicted output beam has waist Wz = Wx = 2.9 cm at the gyrotron window. Cold test measurements using a VNA and a 3-axis scanner were in good agreement with theory with measured beam waists Wz = 2.9 cm and Wx = 2.7 cm. We also installed the IMC in a 110 GHz, 1.5 MW, 3 μs pulsed gyrotron and measured the field pattern with over 40 dB signal to noise accuracy using an rf diode on a 2-axis scanner. Measured beam waists Wz = 4.8 cm and Wx = 4.2 cm compared well with theoretical waists Wz = Wx = 4.7 cm at a plane 124 cm from the gyrotron window.

  11. Calculation of asymptotic and RMS kicks due to higher order modes in the 3.9-GHz cavity

    SciTech Connect

    Bellantoni, L.; Edwards, H.; Wanzenberg, R.; /DESY

    2008-03-01

    FLASH plans to use a 'third harmonic' (3.9 GHz) superconducting cavity to compensate nonlinear distortions of the longitudinal phase space due to the sinusoidal curvature of the cavity voltage of the TESLA 1.3 GHz cavities. Higher order modes (HOMs) in the 3.9 GHz have a significant impact on the dynamics of the electron bunches in a long bunch train. Kicks due to dipole modes can be enhanced along the bunch train depending on the frequency and Q-value of the modes. The enhancement factor for a constant beam offset with respect to the cavity has been calculated. A simple Monte Carlo model of these effects, allowing for scatter in HOM frequencies due to manufacturing variances, has also been implemented and results for both FLASH and for an XFEL-like configuration are presented.

  12. Efficient AlGaN/GaN Linear and Digital-Switch-Mode Power Amplifiers for Operation at 2GHz

    NASA Astrophysics Data System (ADS)

    Maroldt, Stephan; Wiegner, Dirk; Vitanov, Stanislav; Palankovski, Vassil; Quay, Rüdiger; Ambacher, Oliver

    This work addresses the enormous efficiency and linearity potential of optimized AlGaN/GaN high-electron mobility transistors (HEMT) in conventional Doherty linear base-station amplifiers at 2.7GHz. Supported by physical device simulation, the work further elaborates on the use of AlGaN/GaN HEMTs in high-speed current-switch-mode class-D (CMCD)/class-S MMICs for data rates of up to 8Gbit/s equivalent to 2GHz RF-operation. The device needs for switch-mode operation are derived and verified by MMIC results in class-S and class-D operation. To the authors' knowledge, this is the first time 2GHz-equivalent digital-switch-mode RF-operation is demonstrated with GaN HEMTs with high efficiency.

  13. Dual-Band Dual-Mode Substrate Integrated Waveguide Filters with Independently Reconfigurable TE101 Resonant Mode

    PubMed Central

    Wu, Yongle; Chen, Yuqing; Jiao, Lingxiao; Liu, Yuanan; Ghassemlooy, Zabih

    2016-01-01

    A novel perturbation approach using additional metalized via-holes for implementation of the dual-band or wide-band dual-mode substrate integrated waveguide (SIW) filters is proposed in this paper. The independent perturbation on the first resonant mode TE101 can be constructed by applying the proposed perturbation approach, whereas the second resonant mode TE102 is not affected. Thus, new kinds of dual-band or wide-band dual-mode SIW filters with a fixed or an independently reconfigurable low-frequency band have been directly achieved. In order to experimentally verify the proposed design method, four two-cavity dual-band SIW filters, which have different numbers of perturbation via-holes in each cavity, and a two-cavity dual-band SIW filter, which includes four via-holes and eight reconfigurable states in each cavity, are designed and experimentally assessed. The measured results indicate that the available frequency-ratio range from 1 to 1.3 can be realized by using four two-cavity dual-band SIW filters. The center frequency of the first band can be tuned from 4.61 GHz to 5.24 GHz, whereas the center frequency of the second one is fixed at around 6.18 GHz for the two-cavity dual-band SIW filter with four reconfigurable states via-holes. All the simulated and measured results show an acceptable agreement with the predicted data. PMID:27561687

  14. Transverse Mode Multi-Resonant Single Crystal Transducer

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

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

  15. Nitrogen ion implantation into various materials using 28 GHz electron cyclotron resonance ion source

    SciTech Connect

    Shin, Chang Seouk; Lee, Byoung-Seob; Choi, Seyong; Yoon, Jang-Hee; Kim, Hyun Gyu; Ok, Jung-Woo; Park, Jin Yong; Kim, Seong Jun; Bahng, Jungbae; Hong, Jonggi; Won, Mi-Sook; Lee, Seung Wook

    2016-02-15

    The installation of the 28 GHz electron cyclotron resonance ion source (ECRIS) ion implantation beamline was recently completed at the Korea Basic Science Institute. The apparatus contains a beam monitoring system and a sample holder for the ion implantation process. The new implantation system can function as a multipurpose tool since it can implant a variety of ions, ranging hydrogen to uranium, into different materials with precise control and with implantation areas as large as 1–10 mm{sup 2}. The implantation chamber was designed to measure the beam properties with a diagnostic system as well as to perform ion implantation with an in situ system including a mass spectrometer. This advanced implantation system can be employed in novel applications, including the production of a variety of new materials such as metals, polymers, and ceramics and the irradiation testing and fabrication of structural and functional materials to be used in future nuclear fusion reactors. In this investigation, the first nitrogen ion implantation experiments were conducted using the new system. The 28 GHz ECRIS implanted low-energy, multi-charged nitrogen ions into copper, zinc, and cobalt substrates, and the ion implantation depth profiles were obtained. SRIM 2013 code was used to calculate the profiles under identical conditions, and the experimental and simulation results are presented and compared in this report. The depths and ranges of the ion distributions in the experimental and simulation results agree closely and demonstrate that the new system will enable the treatment of various substrates for advanced materials research.

  16. Nitrogen ion implantation into various materials using 28 GHz electron cyclotron resonance ion source.

    PubMed

    Shin, Chang Seouk; Lee, Byoung-Seob; Choi, Seyong; Yoon, Jang-Hee; Kim, Hyun Gyu; Ok, Jung-Woo; Park, Jin Yong; Kim, Seong Jun; Bahng, Jungbae; Hong, Jonggi; Lee, Seung Wook; Won, Mi-Sook

    2016-02-01

    The installation of the 28 GHz electron cyclotron resonance ion source (ECRIS) ion implantation beamline was recently completed at the Korea Basic Science Institute. The apparatus contains a beam monitoring system and a sample holder for the ion implantation process. The new implantation system can function as a multipurpose tool since it can implant a variety of ions, ranging hydrogen to uranium, into different materials with precise control and with implantation areas as large as 1-10 mm(2). The implantation chamber was designed to measure the beam properties with a diagnostic system as well as to perform ion implantation with an in situ system including a mass spectrometer. This advanced implantation system can be employed in novel applications, including the production of a variety of new materials such as metals, polymers, and ceramics and the irradiation testing and fabrication of structural and functional materials to be used in future nuclear fusion reactors. In this investigation, the first nitrogen ion implantation experiments were conducted using the new system. The 28 GHz ECRIS implanted low-energy, multi-charged nitrogen ions into copper, zinc, and cobalt substrates, and the ion implantation depth profiles were obtained. SRIM 2013 code was used to calculate the profiles under identical conditions, and the experimental and simulation results are presented and compared in this report. The depths and ranges of the ion distributions in the experimental and simulation results agree closely and demonstrate that the new system will enable the treatment of various substrates for advanced materials research.

  17. Nitrogen ion implantation into various materials using 28 GHz electron cyclotron resonance ion source

    NASA Astrophysics Data System (ADS)

    Shin, Chang Seouk; Lee, Byoung-Seob; Choi, Seyong; Yoon, Jang-Hee; Kim, Hyun Gyu; Ok, Jung-Woo; Park, Jin Yong; Kim, Seong Jun; Bahng, Jungbae; Hong, Jonggi; Lee, Seung Wook; Won, Mi-Sook

    2016-02-01

    The installation of the 28 GHz electron cyclotron resonance ion source (ECRIS) ion implantation beamline was recently completed at the Korea Basic Science Institute. The apparatus contains a beam monitoring system and a sample holder for the ion implantation process. The new implantation system can function as a multipurpose tool since it can implant a variety of ions, ranging hydrogen to uranium, into different materials with precise control and with implantation areas as large as 1-10 mm2. The implantation chamber was designed to measure the beam properties with a diagnostic system as well as to perform ion implantation with an in situ system including a mass spectrometer. This advanced implantation system can be employed in novel applications, including the production of a variety of new materials such as metals, polymers, and ceramics and the irradiation testing and fabrication of structural and functional materials to be used in future nuclear fusion reactors. In this investigation, the first nitrogen ion implantation experiments were conducted using the new system. The 28 GHz ECRIS implanted low-energy, multi-charged nitrogen ions into copper, zinc, and cobalt substrates, and the ion implantation depth profiles were obtained. SRIM 2013 code was used to calculate the profiles under identical conditions, and the experimental and simulation results are presented and compared in this report. The depths and ranges of the ion distributions in the experimental and simulation results agree closely and demonstrate that the new system will enable the treatment of various substrates for advanced materials research.

  18. Numerical study of the start-up scenario of a 670 GHz gyrotron operation at TE31,8 mode

    NASA Astrophysics Data System (ADS)

    Pu, Ruifeng; Sinitsyn, Oleksandr; Nusinovich, Gregory; Ireap Team

    2011-10-01

    In order to develop a system to detect concealed radioactive materials, we are designing a 670 GHz gyrotron with sufficient power to cause breakdown in the air. Design studies of the cavity and the magnetron injection gun (MIG) of this gyrotron had already been presented. We concluded study of simple start-up regime for this 670GHz gyrotron operating at TE31,8 mode and found that at the fundamental cyclotron harmonics, the operating mode can be excited and the competitor modes will be suppressed. Currently we are studying gyrotron operating on the second cyclotron harmonics using the same electron gun. Preliminary studies show that if the higher harmonics mode is excited first, it will suppress competitors of the fundamental mode. Using available MIG data, we are performing numerical simulation using MAGY. The results of these simulations can be illustrative for our future experiments, and the results of the study will be presented at the conference. Supported by ONR.

  19. Progress in high-temperature oven development for 28 GHz electron cyclotron resonance ion source

    SciTech Connect

    Ohnishi, J. Higurashi, Y.; Nakagawa, T.

    2016-02-15

    We have been developing a high-temperature oven using UO{sub 2} in the 28 GHz superconducting electron cyclotron resonance ion source at RIKEN since 2013. A total of eleven on-line tests were performed. The longest operation time in a single test was 411 h, and the consumption rate of UO{sub 2} was approximately 2.4 mg/h. In these tests, we experienced several problems: the ejection hole of a crucible was blocked with UO{sub 2} and a crucible was damaged because of the reduction of tungsten strength at high temperature. In order to solve these problems, improvements to the crucible shape were made by simulations using ANSYS.

  20. Free-electron maser with high-selectivity Bragg resonator using coupled propagating and trapped modes

    NASA Astrophysics Data System (ADS)

    Ginzburg, N. S.; Golubev, I. I.; Golubykh, S. M.; Zaslavskii, V. Yu.; Zotova, I. V.; Kaminsky, A. K.; Kozlov, A. P.; Malkin, A. M.; Peskov, N. Yu.; Perel'Shteĭn, É. A.; Sedykh, S. N.; Sergeev, A. S.

    2010-10-01

    A free-electron maser (FEM) with a double-mirror resonator involving a new modification of Bragg structures operating on coupled propagating and quasi-cutoff (trapped) modes has been studied. The presence of trapped waves in the feedback chain improves the selectivity of Bragg resonators and ensures stable single-mode generation regime at a considerable superdimensionality of the interaction space. The possibility of using the new feedback mechanism has been confirmed by experiments with a 30-GHz FEM pumped by the electron beam of LIU-3000 (JINR) linear induction accelerator, in which narrow-band generation was obtained at a power of ˜10 MW and a frequency close to the cutoff frequency of the trapped mode excited in the input Bragg reflector.

  1. Analysis of High Order Modes in 1.3 GHZ CW SRF Electron Linac for a Light Source

    SciTech Connect

    Sukhanov, A.; Vostrikov, A.; Yakovlev, V.

    2013-01-01

    Design of a Light Source (LS) based on the continuous wave superconducting RF (CW SRF) electron linac is currently underway. This facility will provide soft coherent X-ray radiation for a braod spectrum of basic research applications. Quality of the X-ray laser radiation is affected by the electron beam parameters such as the stability of the transverse beam position and longitudinal and transverse beam emittances. High order modes (HOMs) excited in the SRF structures by a passing beam may deteriorate the beam quality and affect the beam stability. Deposition of HOM energy in the walls of SRF cavities adds to the heat load of he cryogenic system and leads to the increased cost of building and operation of the linac. In this paper we evaluate effects of HOMs in an LS CW SRF linac based on Tesla-type 9-cell 1.3 GHz cavities. We analyze non-coherent losses and resonance excitation of HOMs. We estimate heat load due to the very high frequency HOMs. We study influence of the HOMs on the transverse beam dynamics.

  2. Temperature and density evolution during decay in a 2.45 GHz hydrogen electron cyclotron resonance plasma: Off-resonant and resonant cases

    NASA Astrophysics Data System (ADS)

    Cortázar, O. D.; Megía-Macías, A.; Vizcaíno-de-Julián, A.

    2013-09-01

    Time resolved electron temperature and density measurements during the decay stage in a hydrogen electron cyclotron resonance (ECR) plasma are presented for a resonance and off-resonance magnetic field configurations. The measurements are conducted on a ECR plasma generator excited at 2.45 GHz denominated test-bench for ion-sources plasma studies at ESS Bilbao. The plasma parameters evolution is studied by Langmuir probe diagnostic with synchronized sample technique developed for repetitive pulsed plasmas with a temporal resolution of 200 ns in typical decay processes of about 40 μs. An afterglow transient is clearly observed in the reflected microwave power signal from the plasma. Simultaneously, the electron temperature evolution shows rebounding peaks that may be related to the interplay between density drop and microwave coupling with deep impact on the Electron Energy Distribution Function. The correlation of such structures with the plasma absorbed power and the coupling quality is also reported.

  3. Temperature and density evolution during decay in a 2.45 GHz hydrogen electron cyclotron resonance plasma: Off-resonant and resonant cases

    SciTech Connect

    Cortázar, O. D.

    2013-09-15

    Time resolved electron temperature and density measurements during the decay stage in a hydrogen electron cyclotron resonance (ECR) plasma are presented for a resonance and off-resonance magnetic field configurations. The measurements are conducted on a ECR plasma generator excited at 2.45 GHz denominated test-bench for ion-sources plasma studies at ESS Bilbao. The plasma parameters evolution is studied by Langmuir probe diagnostic with synchronized sample technique developed for repetitive pulsed plasmas with a temporal resolution of 200 ns in typical decay processes of about 40 μs. An afterglow transient is clearly observed in the reflected microwave power signal from the plasma. Simultaneously, the electron temperature evolution shows rebounding peaks that may be related to the interplay between density drop and microwave coupling with deep impact on the Electron Energy Distribution Function. The correlation of such structures with the plasma absorbed power and the coupling quality is also reported.

  4. Temperature and density evolution during decay in a 2.45 GHz hydrogen electron cyclotron resonance plasma: off-resonant and resonant cases.

    PubMed

    Cortázar, O D; Megía-Macías, A; Vizcaíno-de-Julián, A

    2013-09-01

    Time resolved electron temperature and density measurements during the decay stage in a hydrogen electron cyclotron resonance (ECR) plasma are presented for a resonance and off-resonance magnetic field configurations. The measurements are conducted on a ECR plasma generator excited at 2.45 GHz denominated test-bench for ion-sources plasma studies at ESS Bilbao. The plasma parameters evolution is studied by Langmuir probe diagnostic with synchronized sample technique developed for repetitive pulsed plasmas with a temporal resolution of 200 ns in typical decay processes of about 40 μs. An afterglow transient is clearly observed in the reflected microwave power signal from the plasma. Simultaneously, the electron temperature evolution shows rebounding peaks that may be related to the interplay between density drop and microwave coupling with deep impact on the Electron Energy Distribution Function. The correlation of such structures with the plasma absorbed power and the coupling quality is also reported.

  5. Up to 400 GHz burst-mode pulse generation from a hybrid harmonic mode-locked Er-doped fibre laser

    NASA Astrophysics Data System (ADS)

    Wang, Sheng-Min; Lai, Yinchieh

    2017-02-01

    By inserting a birefringence filter with FSR  =  100 GHz inside a hybrid mode-locked Er-doped fibre laser, we successfully generate ps to sub-ps optical burst pulses with the intra-burst pulse rate up to 400 GHz. Multiplication of the intra-burst pulse rate is attributed to a new effect analogous to rational harmonic mode-locking, which occurs due to the relative alignment of the cavity harmonic frequencies, the external phase modulation induced frequencies, and the filter-selected frequencies.

  6. Trapped modes and resonances in gyrotropic graphene stacks

    NASA Astrophysics Data System (ADS)

    Razzaz, Faroq; Alkanhal, Majeed A. S.

    2017-03-01

    This paper examines the anomalous electromagnetic wave interactions with gyrotropic graphene-dielectric stacks and characterizes their perturbed wave resonances. Expressions for the dispersion relations, trapped mode condition, and the propagating and evanescent modes in the gyrotropic graphene stack have been derived and numerically quantified. The evanescent modes supported in the ambient medium couple as propagating modes in the gyrotropic graphene-dielectric stack at the discrete frequencies of the trapped modes. Valuation of the resonances in the material tensor and the resonances around the trapped modes that result in transmission anomalies (total transmission and total reflection) and field amplifications in the gyrotropic graphene is described. The effects of the chemical potential and the external magnetic field on the number of discrete trapped modes and subsequently on the transmission resonances are numerically assessed.

  7. Photonic switched beamformer implementation for broadband wireless access in transmission and reception modes at 42.7 GHz

    NASA Astrophysics Data System (ADS)

    Piqueras, Miguel A.; Vidal, Borja; Herrera, Javier; Polo, Valentín; Corral, Juan. L.; Martí, Javier

    2005-05-01

    The performance of a 3-bit photonic switched beamformer for phased array antennas based on optical switches and dispersive media is experimentally demonstrated at 42.7 GHz. Both transmission and reception modes have been experimentally tested. Broadband data transmission and radiation pattern measurements are presented.

  8. Structural resonance and mode of flutter of hummingbird tail feathers.

    PubMed

    Clark, Christopher J; Elias, Damian O; Girard, Madeline B; Prum, Richard O

    2013-09-15

    Feathers can produce sound by fluttering in airflow. This flutter is hypothesized to be aeroelastic, arising from the coupling of aerodynamic forces to one or more of the feather's intrinsic structural resonance frequencies. We investigated how mode of flutter varied among a sample of hummingbird tail feathers tested in a wind tunnel. Feather vibration was measured directly at ~100 points across the surface of the feather with a scanning laser Doppler vibrometer (SLDV), as a function of airspeed, Uair. Most feathers exhibited multiple discrete modes of flutter, which we classified into types including tip, trailing vane and torsional modes. Vibratory behavior within a given mode was usually stable, but changes in independent variables such as airspeed or orientation sometimes caused feathers to abruptly 'jump' from one mode to another. We measured structural resonance frequencies and mode shapes directly by measuring the free response of 64 feathers stimulated with a shaker and recorded with the SLDV. As predicted by the aeroelastic flutter hypothesis, the mode shape (spatial distribution) of flutter corresponded to a bending or torsional structural resonance frequency of the feather. However, the match between structural resonance mode and flutter mode was better for tip or torsional mode shapes, and poorer for trailing vane modes. Often, the 3rd bending structural harmonic matched the expressed mode of flutter, rather than the fundamental. We conclude that flutter occurs when airflow excites one or more structural resonance frequencies of a feather, most akin to a vibrating violin string.

  9. Development of a kW Level-200 GHz Gyrotron FU CW GI with an Internal Quasi-optical Mode Convertor

    NASA Astrophysics Data System (ADS)

    Tatematsu, Yoshinori; Yamaguchi, Yuusuke; Idehara, Toshitaka; Ozeki, Takanori; Ikeda, Ryosuke; Kanemaki, Tomohiro; Ogawa, Isamu; Saito, Teruo

    2012-03-01

    Development of gyrotrons with an internal mode convertor has started in Research Center for Development of Far-Infrared Region, University of Fukui (FIR FU). As the first gyrotron of such a kind, we have designed and manufactured Gyrotron FU CW GI. It operates at 203 GHz at fundamental cyclotron resonance. We have designed a cavity and a mode convertor under some constraints such as reuse of an electron gun and small diameter of a magnet bore. Designed output power is about 1 kW. We have succeeded in observation of a circular radiation pattern. The maximum observed output power is 0.5 kW for the setting cathode voltage of 20 kV and the beam current of 0.5 A. This success makes gyrotron development in FIR FU to proceed to a new stage.

  10. Mode couplings and resonance instabilities in dust clusters.

    PubMed

    Qiao, Ke; Kong, Jie; Oeveren, Eric Van; Matthews, Lorin S; Hyde, Truell W

    2013-10-01

    The normal modes for three to seven particle two-dimensional (2D) dust clusters in a complex plasma are investigated using an N-body simulation. The ion wakefield downstream of each particle is shown to induce coupling between horizontal and vertical modes. The rules of mode coupling are investigated by classifying the mode eigenvectors employing the Bessel and trigonometric functions indexed by order integers (m, n). It is shown that coupling only occurs between two modes with the same m and that horizontal modes having a higher shear contribution exhibit weaker coupling. Three types of resonances are shown to occur when two coupled modes have the same frequency. Discrete instabilities caused by both the first and third type of resonances are verified and instabilities caused by the third type of resonance are found to induce melting. The melting procedure is observed to go through a two-step process with the solid-liquid transition closely obeying the Lindemann criterion.

  11. Strong and tunable mode coupling in carbon nanotube resonators

    NASA Astrophysics Data System (ADS)

    Castellanos-Gomez, Andres; Meerwaldt, Harold B.; Venstra, Warner J.; van der Zant, Herre S. J.; Steele, Gary A.

    2012-07-01

    The nonlinear interaction between two mechanical resonances of the same freely suspended carbon nanotube resonator is studied. We find that, in the Coulomb-blockade regime, the nonlinear modal interaction is dominated by single-electron-tunneling processes and that the mode-coupling parameter can be tuned with the gate voltage, allowing both mode-softening and mode-stiffening behaviors. This is in striking contrast to tension-induced mode coupling in strings where the coupling parameter is positive and gives rise to a stiffening of the mode. The strength of the mode coupling in carbon nanotubes in the Coulomb-blockade regime is observed to be 6 orders of magnitude larger than the mechanical-mode coupling in micromechanical resonators.

  12. Whispering gallery mode resonators based on radiation-sensitive materials

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy (Inventor); Maleki, Lutfollah (Inventor); Ilchenko, Vladimir (Inventor); Handley, Timothy A. (Inventor)

    2005-01-01

    Whispering gallery mode (WGM) optical resonators formed of radiation-sensitive materials to allow for permanent tuning of their resonance frequencies in a controlled manner. Two WGM resonators may be cascaded to form a composite filter to produce a second order filter function where at least one WGM resonator is formed a radiation-sensitive material to allow for proper control in the overlap of the two filter functions.

  13. Nonlinear optics and crystalline whispering gallery mode resonators

    NASA Technical Reports Server (NTRS)

    Matsko, Andrey B.; Savchenkov, Anatoliy A.; Ilchenko, Vladimir S.; Maleki, Lute

    2004-01-01

    We report on our recent results concerning fabrication of high-Q whispering gallery mode (WGM) crystalline resonators, and discuss some possible applications of lithium niobate WGM resonators in nonlinear optics and photonics. In particular, we demonstrate experimentally a tunable third-order optical filter fabricated from the three metalized resonators; and report observation of parametric frequency dobuling in a WGM resonator made of periodically poled lithium niobate (PPLN).

  14. A three-mode microstrip resonator and a miniature ultra-wideband filter based on it

    NASA Astrophysics Data System (ADS)

    Belyaev, B. A.; Khodenkov, S. A.; Leksikov, An. A.; Shabanov, V. F.

    2017-06-01

    An original microstrip resonator design with a strip conductor split by a slot at one of its ends is investigated. It is demonstrated that at the optimal slot sizes, when the eigenfrequency of the second oscillation mode hits the center between the first and third oscillation modes, the resonator can work as a thirdorder bandpass filter. The structure formed from only two such resonators electromagnetically coupled by split conductor sections is a miniature six-order wideband filter with high selectivity. The test prototype of the filter with a central passband frequency of 1.2 GHz and a passband width of 0.75 GHz fabricated on a substrate (45 × 11 × 1) mm3 in size with a permittivity of 80 is characterized by minimum loss in a passband of 0.5 dB. The parametric synthesis of the filter structure was performed using electrodynamic analysis of the 3D model. The measured characteristics of the test prototype agree well with the calculated data.

  15. Fine-tuning of whispering gallery modes in on-chip silica microdisk resonators within a full spectral range

    NASA Astrophysics Data System (ADS)

    Henze, Rico; Pyrlik, Christoph; Thies, Andreas; Ward, Jonathan M.; Wicht, Andreas; Benson, Oliver

    2013-01-01

    We investigate an efficient method for fine-tuning whispering gallery mode resonances in disk-type silica microresonators to reach an arbitrary frequency within the free spectral range of the system. This method is based on a post-production hydrofluoric acid etching process to precisely resize the radius of such microresonators. We show the effectiveness of this approach by tuning their resonance frequency within 10 GHz of specific hydrogen cyanide reference lines (P16, P18). This technique allows for simple and exact matching of narrow-linewidth lasers or spectroscopic lines with the high-Q resonances of on-chip silica microresonators.

  16. Frequency flicker of 2.3 GHz AlN-sapphire high-overtone bulk acoustic resonators

    NASA Astrophysics Data System (ADS)

    Boudot, Rodolphe; Martin, Gilles; Friedt, Jean-Michel; Rubiola, Enrico

    2016-12-01

    We report the detailed characterization of 2.3 GHz AlN-Sapphire high-overtone bulk acoustic resonators (HBARs), with a typical loaded Q-factor of 25-30 × 103, 15-20 dB insertion loss, and resonances separated by about 10 MHz. The temperature coefficient of frequency of HBARs is measured to be about -25 ppm/K. We observe at high-input microwave power a significant distortion of the HBAR resonance lineshape, attributed to non-linear effects. The power-induced fractional frequency variation of the HBAR resonance is measured to be about -5 × 10-10/μW. The residual phase noise of a HBAR is measured in the range of -110 to -130 dBrad2/Hz at 1 Hz Fourier frequency, yielding resonator fractional frequency fluctuations at the level of -205 to -225 dB/Hz at 1 Hz and an ultimate HBAR-limited oscillator Allan deviation about 7 × 10-12 at 1 s integration time. The 1/f noise of the HBAR resonator is found to increase with the input microwave power. A HBAR resonator is used for the development of a low phase noise 2.3 GHz oscillator. An absolute phase noise of -60, -120, and -145 dBrad2/Hz for offset frequencies of 10 Hz, 1 kHz, and 10 kHz, respectively, in excellent agreement with the Leeson effect, is measured.

  17. First results of 28 GHz superconducting electron cyclotron resonance ion source for KBSI accelerator

    NASA Astrophysics Data System (ADS)

    Park, Jin Yong; Lee, Byoung-Seob; Choi, Seyong; Kim, Seong Jun; Ok, Jung-Woo; Yoon, Jang-Hee; Kim, Hyun Gyu; Shin, Chang Seouk; Hong, Jonggi; Bahng, Jungbae; Won, Mi-Sook

    2016-02-01

    The 28 GHz superconducting electron cyclotron resonance (ECR) ion source has been developed to produce a high current heavy ion for the linear accelerator at KBSI (Korea Basic Science Institute). The objective of this study is to generate fast neutrons with a proton target via a p(Li,n)Be reaction. The design and fabrication of the essential components of the ECR ion source, which include a superconducting magnet with a liquid helium re-condensed cryostat and a 10 kW high-power microwave, were completed. The waveguide components were connected with a plasma chamber including a gas supply system. The plasma chamber was inserted into the warm bore of the superconducting magnet. A high voltage system was also installed for the ion beam extraction. After the installation of the ECR ion source, we reported the results for ECR plasma ignition at ECRIS 2014 in Russia. Following plasma ignition, we successfully extracted multi-charged ions and obtained the first results in terms of ion beam spectra from various species. This was verified by a beam diagnostic system for a low energy beam transport system. In this article, we present the first results and report on the current status of the KBSI accelerator project.

  18. First results of 28 GHz superconducting electron cyclotron resonance ion source for KBSI accelerator

    SciTech Connect

    Park, Jin Yong; Lee, Byoung-Seob; Choi, Seyong; Kim, Seong Jun; Ok, Jung-Woo; Yoon, Jang-Hee; Kim, Hyun Gyu; Shin, Chang Seouk; Hong, Jonggi; Bahng, Jungbae; Won, Mi-Sook

    2016-02-15

    The 28 GHz superconducting electron cyclotron resonance (ECR) ion source has been developed to produce a high current heavy ion for the linear accelerator at KBSI (Korea Basic Science Institute). The objective of this study is to generate fast neutrons with a proton target via a p(Li,n)Be reaction. The design and fabrication of the essential components of the ECR ion source, which include a superconducting magnet with a liquid helium re-condensed cryostat and a 10 kW high-power microwave, were completed. The waveguide components were connected with a plasma chamber including a gas supply system. The plasma chamber was inserted into the warm bore of the superconducting magnet. A high voltage system was also installed for the ion beam extraction. After the installation of the ECR ion source, we reported the results for ECR plasma ignition at ECRIS 2014 in Russia. Following plasma ignition, we successfully extracted multi-charged ions and obtained the first results in terms of ion beam spectra from various species. This was verified by a beam diagnostic system for a low energy beam transport system. In this article, we present the first results and report on the current status of the KBSI accelerator project.

  19. Robust Sub-harmonic Mixer at 340 GHz Using Intrinsic Resonances of Hammer-Head Filter and Improved Diode Model

    NASA Astrophysics Data System (ADS)

    Wang, Cheng; He, Yue; Lu, Bin; Jiang, Jun; Miao, Li; Deng, Xian-Jin; Xiong, Yong-zhong; Zhang, Jian

    2017-09-01

    This paper presents a sub-harmonic mixer at 340 GHz based on anti-parallel Schottky diodes (SBDs). Intrinsic resonances in low-pass hammer-head filter have been adopted to enhance the isolation for different harmonic components, while greatly minimizing the transmission loss. The application of new DC grounding structure, impedance matching structure, and suspended micro-strip mitigates the negative influences of fabrication errors from metal cavity, quartz substrate, and micro-assembly. An improved lumped element equivalent circuit model of SBDs guarantees the accuracy of simulation, which takes current-voltage (I/V) behavior, capacitance-voltage (C/V) behavior, carrier velocity saturation, DC series resistor, plasma resonance, skin effect, and four kinds of noise generation mechanisms into consideration thoroughly. The measurement indicates that with local oscillating signal of 2 mW, the lowest double sideband conversion loss is 5.5 dB at 339 GHz; the corresponding DSB noise temperature is 757 K. The 3 dB bandwidth of conversion loss is 50 GHz from 317 to 367 GHz.

  20. Contour mode resonators with acoustic reflectors

    DOEpatents

    Olsson, Roy H.; Fleming, James G.; Tuck, Melanie R.

    2008-06-10

    A microelectromechanical (MEM) resonator is disclosed which has a linear or ring-shaped acoustic resonator suspended above a substrate by an acoustic reflector. The acoustic resonator can be formed with a piezoelectric material (e.g. aluminum nitride, zinc oxide or PZT), or using an electrostatically-actuated material. The acoustic reflector (also termed an acoustic mirror) uses alternating sections of a relatively low acoustic impedance Z.sub.L material and a relatively high acoustic impedance Z.sub.H material to isolate the acoustic resonator from the substrate. The MEM resonator, which can be formed on a silicon substrate with conventional CMOS circuitry, has applications for forming oscillators, rf filters, and acoustic sensors.

  1. Multipolar modes in dielectric disk resonator for wireless power transfer

    NASA Astrophysics Data System (ADS)

    Song, Mingzhao; Belov, Pavel; Kapitanova, Polina

    2017-09-01

    We demonstrate a magnetic resonant WPT system based on dielectric disk resonators and investigated the WPT efficiency as a function of separation. It has been demonstrated that the power transfer can be achieved at different multipolar modes. The numerical study shows that the highest WPT efficiency of 99% can be obtained for the MQ mode in an ideal case. However, the efficiency of MQ mode decays much faster than the MD mode which suggests that a trade-off has to be made in the practical WPT system design.

  2. A high-sensitivity 135 GHz millimeter-wave imager by compact split-ring-resonator in 65-nm CMOS

    NASA Astrophysics Data System (ADS)

    Li, Nan; Yu, Hao; Yang, Chang; Shang, Yang; Li, Xiuping; Liu, Xiong

    2015-11-01

    A high-sensitivity 135 GHz millimeter-wave imager is demonstrated in 65 nm CMOS by on-chip metamaterial resonator: a differential transmission-line (T-line) loaded with split-ring-resonator (DTL-SRR). Due to sharp stop-band introduced by the metamaterial load, high-Q oscillatory amplification can be achieved with high sensitivity when utilizing DTL-SRR as quench-controlled oscillator to provide regenerative detection. The developed 135 GHz mm-wave imager pixel has a compact core chip area of 0.0085 mm2 with measured power consumption of 6.2 mW, sensitivity of -76.8 dBm, noise figure of 9.7 dB, and noise equivalent power of 0.9 fW/√{HZ } Hz. Millimeter-wave images has been demonstrated with millimeter-wave imager integrated with antenna array.

  3. Nonlinear tearing modes stabilization by oscillating the resonant surface

    NASA Astrophysics Data System (ADS)

    Yang, Xiaoqing; Wang, Shaojie

    2016-09-01

    The stabilization of the nonlinear tearing mode by rapidly oscillating the resonant surface has been investigated numerically in a large aspect ratio tokamak with a circular cross-section. By means of the radio frequency current drive, the plasma current can be modulated to make the resonant surface (rs) oscillate in time near its mean position. Previous results show that the linear tearing mode can be suppressed by oscillating the resonant surface with a suitable frequency and amplitude. At the nonlinear stage, the tearing mode stabilization shows different properties. The suppression effects not only depend on the modulation frequency and the oscillation width of the resonant surface but also depend on the relative size of χ0 to δ (here, χ0 is the oscillation width of the resonant surface and δ is the width of tearing layer) and the relative width of χ0 to the magnetic island width W.

  4. Nonlinear optics and crystalline whispering gallery mode resonators

    NASA Technical Reports Server (NTRS)

    Matsko, Andrey; Savchenkov, Anatoliy; Ilchenko, Vladimir S.; Maleki, Lute

    2004-01-01

    We report on our recent results concerning fabrication of high-Q whispering gallery mode crystalline resonaors, and discuss some possible applications of lithium niobate WGM resonators in nonlinear optics and photonics.

  5. Whispering Gallery Mode Resonator with Orthogonally Reconfigurable Filter Function

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

    An optical resonator has been developed with reconfigurable filter function that has resonant lines that can be shifted precisely and independently from each other, creating any desirable combination of resonant lines. This is achieved by changing the axial distribution of the effective refractive index of the resonator, which shifts the resonant frequency of particular optical modes, leaving all the rest unchanged. A reconfigurable optical filter is part of the remote chemical detector proposed for the Mars mission (Planetary Instrument Definition and Development Program PIDDP), but it is also useful for photonic communications devices.

  6. Tunable 12×10 GHz mode-locked semiconductor fiber laser incorporating a Mach-Zehnder interferometer filter

    NASA Astrophysics Data System (ADS)

    Wang, Fei

    2011-06-01

    A stable multiwavelength mode-locked semiconductor fiber ring laser incorporating a fiber Mach-Zehnder interferometer (MZI) filter was proposed and experimentally demonstrated. A semiconductor optical amplifier (SOA) serves as an optically controlled mode-locking element due to gain exhaustion caused by external injected optical pulses. Another SOA severs as a constant-gain medium. A fiber MZI filter with a temperature control is incorporated into the fiber ring cavity to acquire a stable and tunable multiwavelength oscillation. Twelve wavelengths are synchronously mode-locked at 10 GHz, pulse width of mode-locked pulse are about 30 ps. Proposed multiwavelength mode-locked semiconductor fiber ring laser has some distinct advantages, such as simple and compact structure, easy integration, convenient tuning, good stability, potential high repetition rate operating, which has potential application in the future WDM communication system.

  7. Femtosecond harmonic mode-locking of a fiber laser at 3.27 GHz using a bulk-like, MoSe2-based saturable absorber.

    PubMed

    Koo, Joonhoi; Park, June; Lee, Junsu; Jhon, Young Min; Lee, Ju Han

    2016-05-16

    We experimentally demonstrate the use of a bulk-like, MoSe2-based saturable absorber (SA) as a passive harmonic mode-locker for the production of femtosecond pulses from a fiber laser at a repetition rate of 3.27 GHz. By incorporating a bulk-like, MoSe2/PVA-composite-deposited side-polished fiber as an SA within an erbium-doped-fiber-ring cavity, mode-locked pulses with a temporal width of 737 fs to 798 fs can be readily obtained at various harmonic frequencies. The fundamental resonance frequency and the maximum harmonic-resonance frequency are 15.38 MHz and 3.27 GHz (212th harmonic), respectively. The temporal and spectral characteristics of the output pulses are systematically investigated as a function of the pump power. The output pulses exhibited Gaussian-temporal shapes irrespective of the harmonic order, and even when their spectra possessed hyperbolic-secant shapes. The saturable absorption and harmonic-mode-locking performance of our prepared SA are compared with those of previously demonstrated SAs that are based on other transition metal dichalcogenides (TMDs). To the best of the authors' knowledge, the repetition rate of 3.27 GHz is the highest frequency that has ever been demonstrated regarding the production of femtosecond pulses from a fiber laser that is based on SA-induced passive harmonic mode-locking.

  8. Optical rogue waves in whispering-gallery-mode resonators

    NASA Astrophysics Data System (ADS)

    Coillet, Aurélien; Dudley, John; Genty, Goëry; Larger, Laurent; Chembo, Yanne K.

    2014-01-01

    We report a theoretical study showing that rogue waves can emerge in whispering-gallery-mode resonators as the result of the chaotic interplay between Kerr nonlinearity and anomalous group-velocity dispersion. The nonlinear dynamics of the propagation of light in a whispering-gallery-mode resonator is investigated using the Lugiato-Lefever equation, and we give evidence of a range of parameters where rare and extreme events associated with non-Gaussian statistics of the field maxima are observed.

  9. Integrated asymmetric whispering gallery mode resonator microcavity optomechanics

    NASA Astrophysics Data System (ADS)

    Soltani, Soheil; Hudnut, Alexa W.; Armani, Andrea M.

    2017-02-01

    Ultra high quality optical resonators have enabled accumulation of exceptionally high intensities of light from low input powers. This feature opens new horizons in low power observation of physical phenomena such as lasing, sensing and radiation pressure driven oscillations. Radiation pressure instability facilitates transfer of energy from photons to mechanical degree of freedom in optical resonators. In high quality toroidal micro cavities, radiation pressure is demonstrated in the form of "dynamic back action" and results mechanical oscillations with sub-Hz linewidth. Since the toroidal cavities are symmetrical in nature, the exerted radiation pressure can mainly excite radially symmetric modes such as the first cantilever mode and the radially breathing mode. Study of these modes reveals important information about interaction of light and mechanical mode as well as intrinsic properties of the resonator as a mechanical oscillator. However, there are some unexcited mechanical modes that in some cases have even higher mechanical quality factors compared to the usually excited ones. Most of the properties of these mechanical modes remain unknown because the radially symmetric force does not provide a component to excite them. In this research, we have developed a novel method to fabricate asymmetric toroidal resonators (minor and major diameters), which enables us to regeneratively excite unobserved asymmetric modes. One key feature is that the optical quality factor is relatively high despite the asymmetry. As a result, we are able to excite the asymmetric modes with sub-mW threshold powers. Complementary modeling is also performed, confirming the experimental findings.

  10. Continuous spectrum of modes for optical micro-sphere resonators

    NASA Astrophysics Data System (ADS)

    Nooramin, Amir Saman; Shahabadi, Mahmoud

    2016-09-01

    This paper presents an improved modal analysis for the spherical dielectric resonator. This is commonly carried out by assuming an outgoing spherical Hankel function for the region surrounding the dielectric sphere. It will be shown that this assumption is incomplete and cannot lead to the entire spectrum of resonance frequencies. Following an analytical formulation, we prove that, like cylindrical resonators, the only choice for the outer region of the dielectric sphere can be a proper linear combination of an inward and an outward traveling wave. Starting from this formulation, we determine the complete spectrum of the resonance frequencies and the associated mode fields. In this analysis, the continuous spectrum of resonance frequencies is introduced and the properties of radiation modes are studied in detail. The proposed analytical formulation is thereafter employed to calculate the quality factor of the resonator due to radiation and dielectric loss.

  11. Tunable GHz pulse repetition rate operation in high-power TEM(00)-mode Nd:YLF lasers at 1047 nm and 1053 nm with self mode locking.

    PubMed

    Huang, Y J; Tzeng, Y S; Tang, C Y; Huang, Y P; Chen, Y F

    2012-07-30

    We report on a high-power diode-pumped self-mode-locked Nd:YLF laser with the pulse repetition rate up to several GHz. A novel tactic is developed to efficiently select the output polarization state for achieving the stable TEM(00)-mode self-mode-locked operations at 1053 nm and 1047 nm, respectively. At an incident pump power of 6.93 W and a pulse repetition rate of 2.717 GHz, output powers as high as 2.15 W and 1.35 W are generated for the σ- and π-polarization, respectively. We experimentally find that decreasing the separation between the gain medium and the input mirror not only brings in the pulse shortening thanks to the enhanced effect of the spatial hole burning, but also effectively introduces the effect of the spectral filtering to lead the Nd:YLF laser to be in a second harmonic mode-locked status. Consequently, pulse durations as short as 8 ps and 8.5 ps are obtained at 1053 nm and 1047 nm with a pulse repetition rate of 5.434 GHz.

  12. Optical filter having coupled whispering-gallery-mode resonators

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy (Inventor); Ilchenko, Vladimir (Inventor); Maleki, Lutfollah (Inventor); Handley, Timothy A. (Inventor)

    2006-01-01

    Optical filters having at least two coupled whispering-gallery-mode (WGM) optical resonators to produce a second order or higher order filter function with a desired spectral profile. At least one of the coupled WGM optical resonators may be tunable by a control signal to adjust the filtering function.

  13. Broadband absorption through extended resonance modes in random metamaterials

    NASA Astrophysics Data System (ADS)

    Hao, J.; Niemiec, R.; Burgnies, L.; Lheurette, É.; Lippens, D.

    2016-05-01

    The properties of disordered metamaterial absorbers are analyzed on the basis of numerical simulations and experimental characterizations. A broadening of the absorption spectrum is clearly evidenced. This effect is the consequence of both the coupling between nearby resonators leading to the occurrence of extended magnetic resonance modes and the interconnection of elementary particles yielding the definition of resonating clusters. The angular robustness of the absorbing structure under oblique incidence is also demonstrated for a wide domain of angles.

  14. Broadband absorption through extended resonance modes in random metamaterials

    SciTech Connect

    Hao, J.; Niemiec, R.; Lheurette, É.; Lippens, D.; Burgnies, L.

    2016-05-21

    The properties of disordered metamaterial absorbers are analyzed on the basis of numerical simulations and experimental characterizations. A broadening of the absorption spectrum is clearly evidenced. This effect is the consequence of both the coupling between nearby resonators leading to the occurrence of extended magnetic resonance modes and the interconnection of elementary particles yielding the definition of resonating clusters. The angular robustness of the absorbing structure under oblique incidence is also demonstrated for a wide domain of angles.

  15. Linear Coupling between Transverse Modes of a Nanomechanical Resonator

    NASA Astrophysics Data System (ADS)

    Truitt, Patrick; Hertzberg, Jared; Schwab, Keith

    2013-03-01

    Recently, several groups have identified a linear coupling between different vibrational modes of nanomechanical resonators. We report observations of such a coupling between the two transverse modes of a doubly-clamped Si3N4 resonator with transverse resonance frequencies of 8.4 and 8.7 MHz. The resonator is voltage biased with respect to a nearby gate electrode for capactive readout. Increasing the gate bias introduces an electrostatic contribution to the spring constant of each mode, reducing the frequency gap between the two modes. At degeneracy, we observe an avoided crossing of 100 kHz. Measurements of the displacement amplitudes and quality factors through degeneracy is consistent with a linear superposition of the two modes. Magnetomotive measurements, which are sensitive to the projection of each mode's displacement onto an applied field, show that the coupled modes remain linearly polarized, with the direction of polarization rotating with increasing gate bias. In an effort to identify the source of the coupling, we constructed a finite element model of the resonator-gate capacitance and find that the observed coupling is an order of magnitude larger than what is expected from electrostatic gradients alone.

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

    PubMed

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

    2015-10-19

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

  17. Modes of resonators with mirror reflectivity modulated by absorbing masks

    SciTech Connect

    De Silvestri, S.; Magni, V.; Svelto, O. )

    1989-09-01

    The modes of a stable laser resonator containing, near one mirror, an absorbing mask with two apertures have been calculated on the basis of scalar diffraction theory and experimentally observed in a pulsed Nd:YAG laser. The mode structure has been investigated as a function of the mask geometry, and an interpretation in terms of supermodes is provided.

  18. Surface vibrational modes in disk-shaped resonators.

    PubMed

    Dmitriev, A V; Gritsenko, D S; Mitrofanov, V P

    2014-03-01

    The natural frequencies and distributions of displacement components for the surface vibrational modes in thin isotropic elastic disks are calculated. In particular, the research is focused on even solutions for low-lying resonant vibrations with large angular wave numbers. Several families of modes are found which are interpreted as modified surface modes of an infinitely long cylinder and Lamb modes of a plate. The results of calculation are compared with the results of the experimental measurements of vibrational modes generated by means of resonant excitation in duraluminum disk with radius of ≈90 mm and thickness of 16 mm in the frequency range of 130-200 kHz. An excellent agreement between the calculated and measured frequencies is found. Measurements of the structure of the resonant peaks show splitting of some modes. About a half of the measured modes has splitting Δfsplit/fmode at the level of the order of 10(-5). The Q-factors of all modes measured in vacuum lie in the interval (2…3)×10(5). This value is typical for duraluminum mechanical resonators in the ultrasonic frequency range.

  19. Wavelength-tunable 10 GHz actively harmonic mode-locked fiber laser based on semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Mao, Yan; Tong, Xinglin; Wang, Zhiqiang; Zhan, Li; Hu, Pan; Chen, Liang

    2015-12-01

    We demonstrate a widely wavelength-tunable actively mode-locked fiber laser based on semiconductor optical amplifier. Beneficiating from the actively mode-locking operation and the wavelength-tunable characteristics of a Fabry-Perot filter, different harmonic mode-locking orders, from the fundamental mode-locking order (18.9 MHz) to the 520th order (9.832 GHz), can be easily achieved. The spectral bandwidth corresponding to the fundamental repetition rate is 0.12 nm with the pulse duration of 9.8 ns, leading to the TBP value of 146, which is about 460 times the transform-limited value for soliton pulse. The highest repetition rate of the mode-locked pulses we obtained is 9.832 GHz, with a signal-to-noise ratio up to 50 dB. The theoretical transform-limited pulse duration is 21 ps. Meanwhile, the central wavelength can be continuously tuned over 43.4 nm range (1522.8-1566.2 nm). The higher repetition rate and the widely tuning wavelength range make the fiber laser to own great potential and promising prospects in areas such as optical communication and photonic analog-to-digital conversion (ADC).

  20. Single-Mode WGM Resonators Fabricated by Diamond Turning

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

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

  1. Large mode-volume, large beta, photonic crystal laser resonator

    SciTech Connect

    Dezfouli, Mohsen Kamandar; Dignam, Marc M.

    2014-12-15

    We propose an optical resonator formed from the coupling of 13, L2 defects in a triangular-lattice photonic crystal slab. Using a tight-binding formalism, we optimized the coupled-defect cavity design to obtain a resonator with predicted single-mode operation, a mode volume five times that of an L2-cavity mode and a beta factor of 0.39. The results are confirmed using finite-difference time domain simulations. This resonator is very promising for use as a single mode photonic crystal vertical-cavity surface-emitting laser with high saturation output power compared to a laser consisting of one of the single-defect cavities.

  2. Analysis of whispering-gallery superconducting dielectric resonator modes

    SciTech Connect

    Zhou Shiping; Jabbar, A. )

    1991-06-01

    The whispering-gallery (WG) modes of a superconducting dielectric resonator (SDR) based on a sapphire cylindrical dielectric resonator and a YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} shielding cylinder were studied. A method for the determination of the resonant frequencies and the maximum quality factor of such modes is presented. Calculations have shown that most of the mode energy could be confined between the caustic surface of the WG modes provided the dimensions of the SDR are properly selected, and a magnitude of 10{sup 9} for Q of the SDR could be estimated. A phenomenal explanation is given to account for such outstanding microwave behavior.

  3. Multiple intersection properties of optical resonance modes in metallic metamaterials

    NASA Astrophysics Data System (ADS)

    Tokuda, Yasunori; Sakaguchi, Koichiro; Yamaguchi, Yuki; Takano, Keisuke

    2017-03-01

    Unusual behavior of Fabry-Perot-like waveguide resonance modes is presented for a quasi-dielectric metamaterial that consists of two metallic sub-wavelength cut-through slit-array slabs separated by an air-gap region. Simulations based on the finite-difference time-domain method were conducted. The unique optical properties were interpreted in terms of multiple intersection of the resonance modes. Depending on the intersection conditions of the optical modes, furthermore, a variety of crossing characteristics, i.e., fade-out crossing with/without an isolated loop, anticrossing with/without intensity reduction, and anticrossing with/without frequency repulsion, were identified for the air-gap dependence of the transmission spectra. These findings, which were obtained by careful observation of the properties of this type of metamaterial, present a novel and interesting aspect of the behavior of the optical resonance modes.

  4. Resonant mode for gravitational wave detectors based on atom interferometry

    NASA Astrophysics Data System (ADS)

    Graham, Peter W.; Hogan, Jason M.; Kasevich, Mark A.; Rajendran, Surjeet

    2016-11-01

    We describe an atom interferometric gravitational wave detector design that can operate in a resonant mode for increased sensitivity. By oscillating the positions of the atomic wave packets, this resonant detection mode allows for coherently enhanced, narrow-band sensitivity at target frequencies. The proposed detector is flexible and can be rapidly switched between broadband and narrow-band detection modes. For instance, a binary discovered in broadband mode can subsequently be studied further as the inspiral evolves by using a tailored narrow-band detector response. In addition to functioning like a lock-in amplifier for astrophysical events, the enhanced sensitivity of the resonant approach also opens up the possibility of searching for important cosmological signals, including the stochastic gravitational wave background produced by inflation. We give an example of detector parameters which would allow detection of inflationary gravitational waves down to ΩGW˜10-14 for a two-satellite space-based detector.

  5. Broadband Finline Ortho-Mode Transducer for the 750-1150 GHz Band

    NASA Astrophysics Data System (ADS)

    Groppi, Christopher E.; Drouet D'Aubigny, Christian Y.; Lichtenberger, Arthur W.; Lyons, Christine M.; Walker, Christopher K.

    2005-05-01

    We present the design and fabrication of a novel full waveguide band ortho-mode transducer (OMT) for operation from 750-1150 GHz, and scalable to frequencies as high as 5 THz. At submillimeter and THz frequencies, quasioptical techniques are generally used to implement dual polarization receiver systems. OMTs offer significantly increased simplicity, eliminating polarization diplexing optics. Since both linear polarizations use the same feedhorn and optics, alignment issues between polarizations are also eliminated. Advances in micromachining technology, semiconductor processing techniques and electromagnetic simulation now allow the design and fabrication of OMTs at frequencies where quasioptical approaches were the only viable option. While most OMTs used for radio as stronomy are derivatives of the Bøifot design, the proposed design uses a finline circuit to separate orthogonal linear polarizations. Unlike Bøifot type designs, the Robinson OMT is fully planar, allowing easy fabrication as a single split block waveguide structure with all ports in one plane. The finline circuit is also planar, and can be fabricated using photolithographic techniques on a thin dielectric substrate. This design uses micromachining technology to fabricate the waveguide splitblock by laser etching a silicon substrate that is later metallized. At lower frequencies, direct micromilling can be used to fabricate the split block directly. The finline chips are fabricated on a thin (1 μm) SOI substrate with thick (5 μm) gold finline metallization, and gold beam leads for chip grounding. This chip construction technique compatible with both direct and laser machined waveguide blocks. Both the waveguide and the finline structures can be scaled to frequencies as high as 5 THz using these fabrication techniques. Feedhorns are integrated with the structure at all three ports to allow testing with a Fourier transform spectrometer and 4He bolometer system. This technique can measure the

  6. Phase Matching of Diverse Modes in a WGM Resonator

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy; Strekalov, Dmitry; Yu, Nan; Matsko, Andrey; Mohageg, Makan; Maleki, Lute

    2008-01-01

    Phase matching of diverse electromagnetic modes (specifically, coexisting optical and microwave modes) in a whispering-gallery-mode (WGM) resonator has been predicted theoretically and verified experimentally. Such phase matching is necessary for storage of microwave/terahertz and optical electromagnetic energy in the same resonator, as needed for exploitation of nonlinear optical phenomena. WGM resonators are used in research on nonlinear optical phenomena at low optical intensities and as a basis for design and fabrication of novel optical devices. Examples of nonlinear optical phenomena recently demonstrated in WGM resonators include low-threshold Raman lasing, optomechanical oscillations, frequency doubling, and hyperparametric oscillations. The present findings regarding phase matching were made in research on low-threshold, strongly nondegenerate parametric oscillations in lithium niobate WGM resonators. The principle of operation of such an oscillator is rooted in two previously observed phenomena: (1) stimulated Raman scattering by polaritons in lithium niobate and (2) phase matching of nonlinear optical processes via geometrical confinement of light. The oscillator is partly similar to terahertz oscillators based on lithium niobate crystals, the key difference being that a novel geometrical configuration of this oscillator supports oscillation in the regime. The high resonance quality factors (Q values) typical of WGM resonators make it possible to achieve oscillation at a threshold signal level much lower than that in a non-WGM-resonator lithium niobate crystal.

  7. Repetition-frequency-tunable mode-locked surface emitting semiconductor laser between 2.78 and 7.87 GHz.

    PubMed

    Wilcox, Keith G; Quarterman, Adrian H; Beere, Harvey E; Ritchie, David A; Tropper, Anne C

    2011-11-07

    We report a repetition frequency tunable, passively mode-locked vertical-external-cavity surface-emitting semiconductor laser (VECSEL) with continuous repetition frequency tuning between 2.78 and 7.87 GHz using mechanical tuning of the laser cavity length. The laser emits near-transform-limited, sub-500-fs pulses over almost an octave tuning range between 2.78 and 5 GHz. At repetition rates above 6 GHz the pulse duration increases to ~2.5 ps. Over the entire tuning range the laser emits an average output power of 40 ± 5 mW in a fundamental transverse mode. The change in pulse duration highlights a change in the dominant modelocking mechanism which forms the pulses. At high repetition frequencies the pulse duration is set by the saturable absorber recovery time. At low repetition frequencies the fluence and peak intensity on the SESAM increases to a point where the fast pulse shaping mechanisms of the optical Stark effect and carrier thermalization dominate the pulse shortening.

  8. A passively mode-locked fiber laser at 1.54 mum with a fundamental repetition frequency reaching 2 GHz.

    PubMed

    McFerran, J J; Nenadovic, L; Swann, W C; Schlager, J B; Newbury, N R

    2007-10-01

    We demonstrate a fundamentally mode-locked fiber laser with a repetition frequency in excess of 2 GHz at a central wavelength of 1.535 mum. Co-doped ytterbium-erbium fiber provides the gain medium for the laser, affording high gain per unit length, while a semiconductor saturable absorber mirror (SAM) provides the pulse shaping mechanism in a standing wave cavity. Results are shown confirming cw mode-locking for 1 GHz and 2 GHz repetition frequency systems. The response of the frequency comb output to pump power variations is shown to follow a single pole response. The timing jitter of a 540MHz repetition-rate laser has been suppressed to below 100 fs through phase-lead compensated feedback to the pump power. Alternatively, a single comb line of a 850MHz repetition-rate laser has been phase-locked to a narrow linewidth cw laser with an in-loop phase jitter of 0.06 rad(2). The laser design is compatible with low-noise oscillator applications.

  9. Transverse mode selection in laser resonators using volume Bragg gratings

    NASA Astrophysics Data System (ADS)

    Anderson, Brian; Venus, George; Ott, Daniel; Divliansky, Ivan; Dawson, Jay W.; Drachenberg, Derrek R.; Messerly, Mike J.; Pax, Paul H.; Tassano, John B.; Glebov, Leonid

    2014-06-01

    Power scaling of high power laser resonators is limited due to several nonlinear effects. Scaling to larger mode areas can offset these effects at the cost of decreased beam quality, limiting the brightness that can be achieved from the multi-mode system. In order to improve the brightness from such multi-mode systems, we present a method of transverse mode selection utilizing volume Bragg gratings (VBGs) as an angular filter, allowing for high beam quality from large mode area laser resonators. An overview of transverse mode selection using VBGs is given, with theoretical models showing the effect of the angular selectivity of transmitting VBGs on the resonator modes. Applications of this ideology to the design of laser resonators, with cavity designs and experimental results presented for three types of multimode solid state lasers: a Nd:YVO4 laser with 1 cm cavity length and 0.8 mm diameter beam with an M2 of 1.1, a multimode diode with diffraction limited far field divergence in the slow axis, and a ribbon fiber laser with 13 cores showing M2 improved from 11.3 to 1.5.

  10. Parametric strong mode-coupling in carbon nanotube mechanical resonators

    NASA Astrophysics Data System (ADS)

    Li, Shu-Xiao; Zhu, Dong; Wang, Xin-He; Wang, Jiang-Tao; Deng, Guang-Wei; Li, Hai-Ou; Cao, Gang; Xiao, Ming; Guo, Guang-Can; Jiang, Kai-Li; Dai, Xing-Can; Guo, Guo-Ping

    2016-08-01

    Carbon nanotubes (CNTs) have attracted much attention for use in nanomechanical devices because of their exceptional properties, such as large resonant frequencies, low mass, and high quality factors. Here, we report the first experimental realization of parametric strong coupling between two mechanical modes on a single CNT nanomechanical resonator, by applying an extra microwave pump. This parametric pump method can be used to couple mechanical modes with arbitrary frequency differences. The properties of the mechanical resonator are detected by single-electron tunneling at low temperature, which is found to be strongly coupled to both modes. The coupling strength between the two modes can be tuned by the pump power, setting the coupling regime from weak to strong. This tunability may be useful in further phonon manipulations in carbon nanotubes.Carbon nanotubes (CNTs) have attracted much attention for use in nanomechanical devices because of their exceptional properties, such as large resonant frequencies, low mass, and high quality factors. Here, we report the first experimental realization of parametric strong coupling between two mechanical modes on a single CNT nanomechanical resonator, by applying an extra microwave pump. This parametric pump method can be used to couple mechanical modes with arbitrary frequency differences. The properties of the mechanical resonator are detected by single-electron tunneling at low temperature, which is found to be strongly coupled to both modes. The coupling strength between the two modes can be tuned by the pump power, setting the coupling regime from weak to strong. This tunability may be useful in further phonon manipulations in carbon nanotubes. Electronic supplementary information (ESI) available: Fit of the quality factor and similar results in more devices. See DOI: 10.1039/c6nr02853e

  11. CW and pulsed electrically detected magnetic resonance spectroscopy at 263GHz/12T on operating amorphous silicon solar cells.

    PubMed

    Akhtar, W; Schnegg, A; Veber, S; Meier, C; Fehr, M; Lips, K

    2015-08-01

    Here we describe a new high frequency/high field continuous wave and pulsed electrically detected magnetic resonance (CW EDMR and pEDMR) setup, operating at 263GHz and resonance fields between 0 and 12T. Spin dependent transport in illuminated hydrogenated amorphous silicon p-i-n solar cells at 5K and 90K was studied by in operando 263GHz CW and pEDMR alongside complementary X-band CW EDMR. Benefiting from the superior resolution at 263GHz, we were able to better resolve EDMR signals originating from spin dependent hopping and recombination processes. 5K EDMR spectra were found to be dominated by conduction and valence band tail states involved in spin dependent hopping, with additional contributions from triplet exciton states. 90K EDMR spectra could be assigned to spin pair recombination involving conduction band tail states and dangling bonds as the dominating spin dependent transport process, with additional contributions from valence band tail and triplet exciton states. Copyright © 2015 Elsevier Inc. All rights reserved.

  12. CW and pulsed electrically detected magnetic resonance spectroscopy at 263 GHz/12 T on operating amorphous silicon solar cells

    NASA Astrophysics Data System (ADS)

    Akhtar, W.; Schnegg, A.; Veber, S.; Meier, C.; Fehr, M.; Lips, K.

    2015-08-01

    Here we describe a new high frequency/high field continuous wave and pulsed electrically detected magnetic resonance (CW EDMR and pEDMR) setup, operating at 263 GHz and resonance fields between 0 and 12 T. Spin dependent transport in illuminated hydrogenated amorphous silicon p-i-n solar cells at 5 K and 90 K was studied by in operando 263 GHz CW and pEDMR alongside complementary X-band CW EDMR. Benefiting from the superior resolution at 263 GHz, we were able to better resolve EDMR signals originating from spin dependent hopping and recombination processes. 5 K EDMR spectra were found to be dominated by conduction and valence band tail states involved in spin dependent hopping, with additional contributions from triplet exciton states. 90 K EDMR spectra could be assigned to spin pair recombination involving conduction band tail states and dangling bonds as the dominating spin dependent transport process, with additional contributions from valence band tail and triplet exciton states.

  13. Imaging the Localized Plasmon Resonance Modes in Graphene Nanoribbons

    DOE PAGES

    Hu, F.; Luan, Y.; Fei, Z.; ...

    2017-08-14

    Here, we report a nanoinfrared (IR) imaging study of the localized plasmon resonance modes of graphene nanoribbons (GNRs) using a scattering-type scanning near-field optical microscope (s-SNOM). By comparing the imaging data of GNRs that are aligned parallel and perpendicular to the in-plane component of the excitation laser field, we observed symmetric and asymmetric plasmonic interference fringes, respectively. Theoretical analysis indicates that the asymmetric fringes are formed due to the interplay between the localized surface plasmon resonance (SPR) mode excited by the GNRs and the propagative surface plasmon polariton (SPP) mode launched by the s-SNOM tip. And with rigorous simulations, wemore » reproduce the observed fringe patterns and address quantitatively the role of the s-SNOM tip on both the SPR and SPP modes. Moreover, we have seen real-space signatures of both the dipole and higher-order SPR modes by varying the ribbon width.« less

  14. Imaging the Localized Plasmon Resonance Modes in Graphene Nanoribbons.

    PubMed

    Hu, F; Luan, Y; Fei, Z; Palubski, I Z; Goldflam, M D; Dai, S; Wu, J-S; Post, K W; Janssen, G C A M; Fogler, M M; Basov, D N

    2017-09-13

    We report a nanoinfrared (IR) imaging study of the localized plasmon resonance modes of graphene nanoribbons (GNRs) using a scattering-type scanning near-field optical microscope (s-SNOM). By comparing the imaging data of GNRs that are aligned parallel and perpendicular to the in-plane component of the excitation laser field, we observed symmetric and asymmetric plasmonic interference fringes, respectively. Theoretical analysis indicates that the asymmetric fringes are formed due to the interplay between the localized surface plasmon resonance (SPR) mode excited by the GNRs and the propagative surface plasmon polariton (SPP) mode launched by the s-SNOM tip. With rigorous simulations, we reproduce the observed fringe patterns and address quantitatively the role of the s-SNOM tip on both the SPR and SPP modes. Furthermore, we have seen real-space signatures of both the dipole and higher-order SPR modes by varying the ribbon width.

  15. Anisotropic resonance modes emerging in an antiferromagnetic superconducting state.

    PubMed

    Waßer, F; Lee, C H; Kihou, K; Steffens, P; Schmalzl, K; Qureshi, N; Braden, M

    2017-09-04

    Two strong arguments in favor of magnetically driven unconventional superconductivity arise from the coexistence and closeness of superconducting and magnetically ordered phases on the one hand, and from the emergence of magnetic spin-resonance modes at the superconducting transition on the other hand. Combining these two arguments one may ask about the nature of superconducting spin-resonance modes occurring in an antiferromagnetic state. This problem can be studied in underdoped BaFe2 As2, for which the local coexistence of large moment antiferromagnetism and superconductivity is well established by local probes. However, polarized neutron scattering experiments are required to identify the nature of the resonance modes. In the normal state of Co underdoped BaFe2 As2 the antiferromagnetic order results in broad magnetic gaps opening in all three spin directions that are reminiscent of the magnetic response in the parent compound. In the superconducting state two distinct anisotropic resonance excitations emerge, but in contrast to numerous studies on optimum and over-doped BaFe2 As2 there is no isotropic resonance excitation. The two anisotropic resonance modes appearing within the antiferromagnetic phase are attributed to a band selective superconducting state, in which longitudinal magnetic excitations are gapped by antiferromagnetic order with sizable moment.

  16. Rapid scan electron paramagnetic resonance at 1.0 GHz of defect centers in γ-irradiated organic solids.

    PubMed

    Shi, Yilin; Rinard, George A; Quine, Richard W; Eaton, Sandra S; Eaton, Gareth R

    2016-02-01

    The radicals in six (60)Co γ-irradiated solids: malonic acid, glycylglycine, 2,6 di-t-butyl 4-methyl phenol, L-alanine, dimethyl malonic acid, and 2-amino isobutyric acid, were studied by rapid scan electron paramagnetic resonance at L-band (1.04 GHz) using a customized Bruker Elexsys spectrometer and a locally-designed dielectric resonator. Sinusoidal scans with widths up to 18.2 mT were generated with the recently described coil driver and Litz wire coils. Power saturation curves showed that the rapid scan signals saturated at higher powers than did conventional continuous wave signals. The rapid scan data were deconvolved and background subtracted to obtain absorption spectra. For the same data acquisition time the signal-to-noise for the absorption spectra obtained in rapid scans were 23 to 37 times higher than for first-derivative spectra obtained by conventional continuous wave electron paramagnetic resonance.

  17. Rapid scan electron paramagnetic resonance at 1.0 GHz of defect centers in γ-irradiated organic solids

    PubMed Central

    Shi, Yilin; Rinard, George A.; Quine, Richard W.; Eaton, Sandra S.; Eaton, Gareth R.

    2016-01-01

    The radicals in six 60Co γ-irradiated solids: malonic acid, glycylglycine, 2,6 di-t-butyl 4-methyl phenol, L-alanine, dimethyl malonic acid, and 2-amino isobutyric acid, were studied by rapid scan electron paramagnetic resonance at L-band (1.04 GHz) using a customized Bruker Elexsys spectrometer and a locally-designed dielectric resonator. Sinusoidal scans with widths up to 18.2 mT were generated with the recently described coil driver and Litz wire coils. Power saturation curves showed that the rapid scan signals saturated at higher powers than did conventional continuous wave signals. The rapid scan data were deconvolved and background subtracted to obtain absorption spectra. For the same data acquisition time the signal-to-noise for the absorption spectra obtained in rapid scans were 23 to 37 times higher than for first-derivative spectra obtained by conventional continuous wave electron paramagnetic resonance. PMID:26834505

  18. Passive mode-locking of fiber ring laser at the 337th harmonic using gigahertz acoustic core resonances.

    PubMed

    Kang, M S; Joly, N Y; Russell, P St J

    2013-02-15

    We report the experimental demonstration of a passively mode-locked Er-doped fiber ring laser operating at the 337th harmonic (1.80 GHz) of the cavity. The laser makes use of highly efficient Raman-like optoacoustic interactions between the guided light and gigahertz acoustic resonances trapped in the micron-sized solid glass core of a photonic crystal fiber. At sufficient pump power levels the laser output locks to a repetition rate corresponding to the acoustic frequency. A stable optical pulse train with a side-mode suppression ratio higher than 45 dB was obtained at low pump powers (~60 mW).

  19. Center Frequency Stabilization in Planar Dual-Mode Resonators during Mode-Splitting Control

    NASA Astrophysics Data System (ADS)

    Naji, Adham; Soliman, Mina H.

    2017-03-01

    Shape symmetry in dual-mode planar electromagnetic resonators results in their ability to host two degenerate resonant modes. As the designer enforces a controllable break in the symmetry, the degeneracy is removed and the two modes couple, exchanging energy and elevating the resonator into its desirable second-order resonance operation. The amount of coupling is controlled by the degree of asymmetry introduced. However, this mode coupling (or splitting) usually comes at a price. The centre frequency of the perturbed resonator is inadvertently drifted from its original value prior to coupling. Maintaining centre frequency stability during mode splitting is a nontrivial geometric design problem. In this paper, we analyse the problem and propose a novel method to compensate for this frequency drift, based on field analysis and perturbation theory, and we validate the solution through a practical design example and measurements. The analytical method used works accurately within the perturbational limit. It may also be used as a starting point for further numerical optimization algorithms, reducing the required computational time during design, when larger perturbations are made to the resonator. In addition to enabling the novel design example presented, it is hoped that the findings will inspire akin designs for other resonator shapes, in different disciplines and applications.

  20. Center Frequency Stabilization in Planar Dual-Mode Resonators during Mode-Splitting Control.

    PubMed

    Naji, Adham; Soliman, Mina H

    2017-03-08

    Shape symmetry in dual-mode planar electromagnetic resonators results in their ability to host two degenerate resonant modes. As the designer enforces a controllable break in the symmetry, the degeneracy is removed and the two modes couple, exchanging energy and elevating the resonator into its desirable second-order resonance operation. The amount of coupling is controlled by the degree of asymmetry introduced. However, this mode coupling (or splitting) usually comes at a price. The centre frequency of the perturbed resonator is inadvertently drifted from its original value prior to coupling. Maintaining centre frequency stability during mode splitting is a nontrivial geometric design problem. In this paper, we analyse the problem and propose a novel method to compensate for this frequency drift, based on field analysis and perturbation theory, and we validate the solution through a practical design example and measurements. The analytical method used works accurately within the perturbational limit. It may also be used as a starting point for further numerical optimization algorithms, reducing the required computational time during design, when larger perturbations are made to the resonator. In addition to enabling the novel design example presented, it is hoped that the findings will inspire akin designs for other resonator shapes, in different disciplines and applications.

  1. Center Frequency Stabilization in Planar Dual-Mode Resonators during Mode-Splitting Control

    PubMed Central

    Naji, Adham; Soliman, Mina H.

    2017-01-01

    Shape symmetry in dual-mode planar electromagnetic resonators results in their ability to host two degenerate resonant modes. As the designer enforces a controllable break in the symmetry, the degeneracy is removed and the two modes couple, exchanging energy and elevating the resonator into its desirable second-order resonance operation. The amount of coupling is controlled by the degree of asymmetry introduced. However, this mode coupling (or splitting) usually comes at a price. The centre frequency of the perturbed resonator is inadvertently drifted from its original value prior to coupling. Maintaining centre frequency stability during mode splitting is a nontrivial geometric design problem. In this paper, we analyse the problem and propose a novel method to compensate for this frequency drift, based on field analysis and perturbation theory, and we validate the solution through a practical design example and measurements. The analytical method used works accurately within the perturbational limit. It may also be used as a starting point for further numerical optimization algorithms, reducing the required computational time during design, when larger perturbations are made to the resonator. In addition to enabling the novel design example presented, it is hoped that the findings will inspire akin designs for other resonator shapes, in different disciplines and applications. PMID:28272422

  2. Mode competition and mode control in free electron lasers with one and two dimensional Bragg resonators

    SciTech Connect

    Yu, P.N.; Ginzburg, N.S.; Sergeev, A.S.

    1995-12-31

    In the report we present a time domain approach to the theory of FELs with one and two dimensional Bragg resonators. It is demonstrated that traditional 1-D Bragg resonators provide possibilities for effective longitudinal mode control. In particular, simulation of the FEL realized in the joint experiment of JINR (Dybna) and IAP (N. Novgord) confirms achievement of the single mode operating regime with high efficiency of about 20%. However, 1-D Bragg resonators lose their selectivity as the transverse size of the system is increased. We simulate mode competition in FELs with coaxial 1-D Bragg resonators and observe a progressively more complicated azimuthal mode competition pattern as the perimeter of the resonator is increased. At the same time, using 2-D Bragg resonators for the same electron beam and microwave system perimeter gives very fast establishment of the single frequency regime with an azimuthally symmetric operating mode. Therefore, FELs utilising 2-D Bragg resonators with coaxial and planar geometry may be considered as attractive sources of high power spatially coherent radiation in the mm and sub-mm wave bands.

  3. Active mode-locked lasers and other photonic devices using electro-optic whispering gallery mode resonators

    NASA Technical Reports Server (NTRS)

    Matsko, Andrey B. (Inventor); Ilchenko, Vladimir (Inventor); Savchenkov, Anatoliy (Inventor); Maleki, Lutfollah (Inventor)

    2006-01-01

    Techniques and devices using whispering gallery mode (WGM) optical resonators, where the optical materials of the WGM resonators exhibit an electro-optical effect to perform optical modulation. Examples of actively mode-locked lasers and other devices are described.

  4. Resonant Mode Reduction in Radiofrequency Volume Coils for Ultrahigh Field Magnetic Resonance Imaging.

    PubMed

    Pang, Yong; Xie, Zhentian; Li, Ye; Xu, Duan; Vigneron, Daniel; Zhang, Xiaoliang

    2011-07-28

    In a multimodal volume coil, only one mode can generate homogeneous Radiofrequency (RF) field for Magnetic Resonance Imaging. The existence of other modes may increase the volume coil design difficulties and potentially decreases coil performance. In this study, we introduce common-mode resonator technique to high and ultrahigh field volume coil designs to reduce the resonant mode while maintain the homogeneity of the RF field. To investigate the design method, the common-mode resonator was realized by using a microstrip line which was split along the central to become a pair of parallel transmission lines within which common-mode currents exist. Eight common-mode resonators were placed equidistantly along the circumference of a low loss dielectric cylinder to form a volume coil. Theoretical analysis and comparison between the 16-strut common-mode volume coil and a conventional 16-strut volume coil in terms of RF field homogeneity and efficiency was performed using Finite-Difference Time-Domain (FDTD) method at 298.2 MHz. MR imaging experiments were performed by using a prototype of the common-mode volume coil on a whole body 7 Tesla scanner. FDTD simulation results showed the reduced number of resonant modes of the common-mode volume coil over the conventional volume coil, while the RF field homogeneity of the two type volume coils was kept at the same level. MR imaging of a water phantom and a kiwi fruit showing the feasibility of the proposed method for simplifying the volume coil design is also presented.

  5. Under-Coupling Whispering Gallery Mode Resonator Applied to Resonant Micro-Optic Gyroscope.

    PubMed

    Qian, Kun; Tang, Jun; Guo, Hao; Liu, Wenyao; Liu, Jun; Xue, Chenyang; Zheng, Yongqiu; Zhang, Chengfei

    2017-01-06

    As an important sensing element, the whispering gallery mode resonator (WGMR) parameters seriously affect the resonant micro-optic gyroscope (RMOG) performance. This work proposes an under-coupling resonator to improve the resonator's Q value and to optimize the coupling coefficient to maximize the RMOG's sensitivity. GeO₂-doped silica waveguide-type resonators with different coupling coefficients were simulated, designed, fabricated and tested. An under-coupling ring resonator with a quality factor of 10 million is reported. The RMOG system was built based on this resonator and the scale factor was tested on a uniaxial high-precision rotating platform. Experimental results show that this resonator could improve the RMOG sensitivity by five times.

  6. Resonant mode controllers for launch vehicle applications

    NASA Astrophysics Data System (ADS)

    Schreiner, Ken E.; Roth, Mary Ellen

    Electro-mechanical actuator (EMA) systems are currently being investigated for the National Launch System (NLS) as a replacement for hydraulic actuators due to the large amount of manpower and support hardware required to maintain the hydraulic systems. EMA systems in weight sensitive applications, such as launch vehicles, have been limited to around 5 hp due to system size, controller efficiency, thermal management, and battery size. Presented here are design and test data for an EMA system that competes favorably in weight and is superior in maintainability to the hydraulic system. An EMA system uses dc power provided by a high energy density bipolar lithium thionyl chloride battery, with power conversion performed by low loss resonant topologies, and a high efficiency induction motor controlled with a high performance field oriented controller to drive a linear actuator.

  7. Resonant mode controllers for launch vehicle applications

    NASA Technical Reports Server (NTRS)

    Schreiner, Ken E.; Roth, Mary Ellen

    1992-01-01

    Electro-mechanical actuator (EMA) systems are currently being investigated for the National Launch System (NLS) as a replacement for hydraulic actuators due to the large amount of manpower and support hardware required to maintain the hydraulic systems. EMA systems in weight sensitive applications, such as launch vehicles, have been limited to around 5 hp due to system size, controller efficiency, thermal management, and battery size. Presented here are design and test data for an EMA system that competes favorably in weight and is superior in maintainability to the hydraulic system. An EMA system uses dc power provided by a high energy density bipolar lithium thionyl chloride battery, with power conversion performed by low loss resonant topologies, and a high efficiency induction motor controlled with a high performance field oriented controller to drive a linear actuator.

  8. Development of a Submillimeter Double-Ridged Waveguide Ortho-Mode Transducer (OMT) for the 385-500 GHz Band

    NASA Astrophysics Data System (ADS)

    Kamikura, Mamoru; Naruse, Masato; Asayama, Shin'ichiro; Satou, Naohisa; Shan, Wenlei; Sekimoto, Yutaro

    2010-06-01

    We present design and evaluations of a submillimeter double-ridged waveguide ortho-mode transducer (OMT) for ALMA Band 8 (385-500 GHz) cartridge receiver. The measured transmission loss of the OMT at 4 K was 0.4-0.5 dB according to noise measurements with an SIS mixer. The polarization isolation was measured to be larger than 29 dB from quasioptical measurements. The OMT consists of a Bϕifot junction and a double-ridged guide. A robust design with allowable mechanical errors of 20 μm has been demonstrated.

  9. 115 W, 10 GHz, femtosecond pulses from a very-large-mode-area Er-doped fiber amplifier

    NASA Astrophysics Data System (ADS)

    Nicholson, J. W.; Ahmad, R.; DeSantolo, A.; Várallyay, Z.

    2017-02-01

    We demonstrate high average power, high peak power amplification of 10 GHz, picosecond and femtosecond pulses in a Very-Large-Mode Area (VLMA), Er-doped fiber with an effective area of 1050 μm2. A high power, singlemode Raman fiber laser with up to 183 W of power at 1480 nm served as a pump source. 130 femtosecond pulses with an average power of 115 W, peak power of 88 kW, and M2 of 1.18 were achieved. Simulations that take into account pair-induced quenching give excellent agreement with measurements.

  10. Nonlinear normal modes modal interactions and isolated resonance curves

    DOE PAGES

    Kuether, Robert J.; Renson, L.; Detroux, T.; ...

    2015-05-21

    The objective of the present study is to explore the connection between the nonlinear normal modes of an undamped and unforced nonlinear system and the isolated resonance curves that may appear in the damped response of the forced system. To this end, an energy balance technique is used to predict the amplitude of the harmonic forcing that is necessary to excite a specific nonlinear normal mode. A cantilever beam with a nonlinear spring at its tip serves to illustrate the developments. Furthermore, the practical implications of isolated resonance curves are also discussed by computing the beam response to sine sweepmore » excitations of increasing amplitudes.« less

  11. Nonlinear normal modes modal interactions and isolated resonance curves

    SciTech Connect

    Kuether, Robert J.; Renson, L.; Detroux, T.; Grappasonni, C.; Kerschen, G.; Allen, M. S.

    2015-05-21

    The objective of the present study is to explore the connection between the nonlinear normal modes of an undamped and unforced nonlinear system and the isolated resonance curves that may appear in the damped response of the forced system. To this end, an energy balance technique is used to predict the amplitude of the harmonic forcing that is necessary to excite a specific nonlinear normal mode. A cantilever beam with a nonlinear spring at its tip serves to illustrate the developments. Furthermore, the practical implications of isolated resonance curves are also discussed by computing the beam response to sine sweep excitations of increasing amplitudes.

  12. Electron acceleration by Landau resonance with whistler mode wave packets

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Reinleitner, L. A.

    1983-01-01

    Recent observations of electrostatic waves associated with whistler mode chorus emissions provide evidence that electrons are being trapped by Landau resonance interactions with the chorus. In this paper, the trapping, acceleration and escape of electrons in Landau resonance with a whistler mode wave packet are discussed. It is shown that acceleration can occur by both inhomogeneous and dispersive effects. The maximum energy gained is controlled by the points where trapping and escape occur. Large energy changes are possible if the frequency of the wave packet or the magnetic field strength increase between the trapping and escape points. Various trapping and escape mechanisms are discussed.

  13. Electron acceleration by Landau resonance with whistler mode wave packets

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Reinleitner, L. A.

    1983-01-01

    Recent observations of electrostatic waves associated with whistler mode chorus emissions provide evidence that electrons are being trapped by Landau resonance interactions with the chorus. In this paper, the trapping, acceleration and escape of electrons in Landau resonance with a whistler mode wave packet are discussed. It is shown that acceleration can occur by both inhomogeneous and dispersive effects. The maximum energy gained is controlled by the points where trapping and escape occur. Large energy changes are possible if the frequency of the wave packet or the magnetic field strength increase between the trapping and escape points. Various trapping and escape mechanisms are discussed.

  14. Comparison of shear flow formation between resonant and non-resonant resistive interchange modes

    NASA Astrophysics Data System (ADS)

    Unemura, T.; Hamaguchi, S.; Wakatani, M.

    1999-11-01

    It is known that the poloidal shear flow is produced from the nonlinear resistive interchange modes(A. Hasegawa and M. Wakatani, Phys. Rev. Lett. 59) 1581 (1987)(B.A. Carreras and V. E. Lynch, Phys. Fluids B 5) 1795 (1993). Since the non-resonant resistive modes also become unstable(K. Ichiguchi, Y. Nakamura and M. Wakatani, Nucl. Fusion 31) 2073 (1991), the nonlinear behavior is compared between the resonant and non-resonant modes from the point of view of poloidal flow formation. For understanding the difference, we studied single helicity (m,n)=(3,2) mode in a cylindrical geometry.Rotational transform profile, ι(r), was changed. First, we assumed ι(r)=0.51+0.39r^2, and increased ι(0). This change represents a finite beta effect in currentless stellarators. When the resonant surface exists with ι(r_s)=2/3, the poloidal flow are created near the resonant surface. And, in the case when no resonant surface exists but ι_min ~ 2/3, the non-resonant (3,2) mode grows and poloidal shear flow is also generated; however, the magnitude decreases sharply with the increase of ι_min.

  15. Guided-mode resonance nanophotonics: fundamentals and applications

    NASA Astrophysics Data System (ADS)

    Magnusson, Robert; Ko, Yeong Hwan

    2016-09-01

    We review principles and applications of nanophotonic devices based on electromagnetic resonance effects in thin periodic films. We discuss the fundamental resonance dynamics that are based on lateral Bloch modes excited by evanescent diffraction orders in these subwavelength devices. Theoretical and experimental results for selected example devices are furnished. Ultra-sparse nanogrids with duty cycle less than 10% are shown to provide substantially wide reflection bands and operate as effective polarizers. Narrow-passband resonant filters with extensive low sidebands are presented with focus on the zero-contrast grating architecture. This study is extended to long-wave operation in the THz region. Examples of fabricated guided-mode resonance devices with outstanding performance are given. This includes an unpolarized wideband reflector using serial single-layer reflectors, an ultra-sparse silicon nanowire grid as wideband reflector and polarizer, resonant bandpass filter with wide low sidebands, and a spatial/spectral filter permitting compact nonfocusing spatial filtering. The guided-mode resonance concept applies in all spectral regions, from the visible band to the microwave domain, with available low-loss materials.

  16. Emittance study of a 28 GHz electron cyclotron resonance ion source for the Rare Isotope Science Project superconducting linear accelerator.

    PubMed

    Park, Bum-Sik; Hong, In-Seok; Jang, Ji-Ho; Jin, Hyunchang; Choi, Sukjin; Kim, Yonghwan

    2016-02-01

    A 28 GHz electron cyclotron resonance (ECR) ion source is being developed for use as an injector for the superconducting linear accelerator of the Rare Isotope Science Project. Beam extraction from the ECR ion source has been simulated using the KOBRA3-INP software. The simulation software can calculate charged particle trajectories in three dimensional complex magnetic field structures, which in this case are formed by the arrangement of five superconducting magnets. In this study, the beam emittance is simulated to understand the effects of plasma potential, mass-to-charge ratio, and spatial distribution. The results of these simulations and their comparison to experimental results are presented in this paper.

  17. Emittance study of a 28 GHz electron cyclotron resonance ion source for the Rare Isotope Science Project superconducting linear accelerator

    SciTech Connect

    Park, Bum-Sik Hong, In-Seok; Jang, Ji-Ho; Jin, Hyunchang; Choi, Sukjin; Kim, Yonghwan

    2016-02-15

    A 28 GHz electron cyclotron resonance (ECR) ion source is being developed for use as an injector for the superconducting linear accelerator of the Rare Isotope Science Project. Beam extraction from the ECR ion source has been simulated using the KOBRA3-INP software. The simulation software can calculate charged particle trajectories in three dimensional complex magnetic field structures, which in this case are formed by the arrangement of five superconducting magnets. In this study, the beam emittance is simulated to understand the effects of plasma potential, mass-to-charge ratio, and spatial distribution. The results of these simulations and their comparison to experimental results are presented in this paper.

  18. Power generation in a resonant cavity using a beam bunched at 35 GHz by a free electron laser

    NASA Astrophysics Data System (ADS)

    Donohue, J. T.; Gardelle, J.; Lefevre, T.; Rullier, J. L.; Vermare, C.; Lidia, S. M.; Meurdesoif, Y.

    2000-05-01

    An intense beam of relativistic electrons (800 A, 6.7 MeV) has been bunched at 35 GHz by a free-electron laser, in which output power levels exceeding 100 MW were obtained. The beam was then extracted and transported through a resonant cavity, that was excited by its passage. Microwave power levels of 10 MW were extracted from the cavity, in reasonable agreement with a simple formula which relates power output to known properties of the both beam and cavity.

  19. Emittance study of a 28 GHz electron cyclotron resonance ion source for the Rare Isotope Science Project superconducting linear accelerator

    NASA Astrophysics Data System (ADS)

    Park, Bum-Sik; Hong, In-Seok; Jang, Ji-Ho; Jin, Hyunchang; Choi, Sukjin; Kim, Yonghwan

    2016-02-01

    A 28 GHz electron cyclotron resonance (ECR) ion source is being developed for use as an injector for the superconducting linear accelerator of the Rare Isotope Science Project. Beam extraction from the ECR ion source has been simulated using the KOBRA3-INP software. The simulation software can calculate charged particle trajectories in three dimensional complex magnetic field structures, which in this case are formed by the arrangement of five superconducting magnets. In this study, the beam emittance is simulated to understand the effects of plasma potential, mass-to-charge ratio, and spatial distribution. The results of these simulations and their comparison to experimental results are presented in this paper.

  20. Left-handed compact MIMO antenna array based on wire spiral resonator for 5-GHz wireless applications

    NASA Astrophysics Data System (ADS)

    Alqadami, Abdulrahman Shueai Mohsen; Jamlos, Mohd Faizal; Soh, Ping Jack; Rahim, Sharul Kamal Abdul; Narbudowicz, Adam

    2017-01-01

    A compact coplanar waveguide-fed multiple-input multiple-output antenna array based on the left-handed wire loaded spiral resonators (SR) is presented. The proposed antenna consists of a 2 × 2 wire SR with two symmetrical microstrip feed lines, each line exciting a 1 × 2 wire SR. Left-handed metamaterial unit cells are placed on its reverse side and arranged in a 2 × 3 array. A reflection coefficient of less than -16 dB and mutual coupling of less than -28 dB are achieved at 5.15 GHz WLAN band.

  1. Uniform field loop-gap resonator and rectangular TEU02 for aqueous sample EPR at 94GHz.

    PubMed

    Sidabras, Jason W; Sarna, Tadeusz; Mett, Richard R; Hyde, James S

    2017-09-01

    In this work we present the design and implementation of two uniform-field resonators: a seven-loop-six-gap loop-gap resonator (LGR) and a rectangular TEU02 cavity resonator. Each resonator has uniform-field-producing end-sections. These resonators have been designed for electron paramagnetic resonance (EPR) of aqueous samples at 94GHz. The LGR geometry employs low-loss Rexolite end-sections to improve the field homogeneity over a 3mm sample region-of-interest from near-cosine distribution to 90% uniform. The LGR was designed to accommodate large degassable Polytetrafluorethylen (PTFE) tubes (0.81mm O.D.; 0.25mm I.D.) for aqueous samples. Additionally, field modulation slots are designed for uniform 100kHz field modulation incident at the sample. Experiments using a point sample of lithium phthalocyanine (LiPC) were performed to measure both the uniformity of the microwave magnetic field and 100kHz field modulation, and confirm simulations. The rectangular TEU02 cavity resonator employs over-sized end-sections with sample shielding to provide an 87% uniform field for a 0.1×2×6mm(3) sample geometry. An evanescent slotted window was designed for light access to irradiate 90% of the sample volume. A novel dual-slot iris was used to minimize microwave magnetic field perturbations and maintain cross-sectional uniformity. Practical EPR experiments using the application of light irradiated rose bengal (4,5,6,7-tetrachloro-2',4',5',7'-tetraiodofluorescein) were performed in the TEU02 cavity. The implementation of these geometries providing a practical designs for uniform field resonators that continue resonator advancements towards quantitative EPR spectroscopy. Copyright © 2017 Elsevier Inc. All rights reserved.

  2. Indirect coupling between two cavity modes via ferromagnetic resonance

    NASA Astrophysics Data System (ADS)

    Hyde, Paul; Bai, Lihui; Harder, Michael; Match, Christophe; Hu, Can-Ming

    2016-10-01

    We experimentally realize an indirect coupling between two cavity modes via strong coupling with ferromagnetic resonance in Yttrium Iron Garnet. We find that some indirectly coupled modes of this system can have a higher microwave transmission than the individual uncoupled modes. Using a coupled harmonic oscillator model, the influence of the oscillation phase difference between the two cavity modes on the nature of the indirect coupling is revealed. The properties of the indirectly coupled modes can be controlled using an external magnetic field or by tuning the cavity height. The relation between cavity transmission and the relative phase difference between cavity modes should be useful for developing tunable optical devices and improved information processing technologies.

  3. Quasilocalization of gravity on a brane by resonant modes.

    PubMed

    Csáki, C; Erlich, J; Hollowood, T J

    2000-06-26

    We examine the behavior of gravity in brane theories with extra dimensions in a nonfactorizable background geometry. We find that for metrics which are asymptotically flat far from the brane there is a resonant graviton mode at zero energy. The presence of this resonance ensures quasilocalization of gravity, whereby at intermediate scales the gravitational laws on the brane are approximately four dimensional. However, for scales larger than the lifetime of the graviton resonance the five-dimensional laws of gravity will be reproduced due to the decay of the four-dimensional graviton. We also give a simple classification of effective gravity theories for general background geometries.

  4. Theory of anisotropic whispering-gallery-mode resonators

    SciTech Connect

    Ornigotti, Marco

    2011-07-15

    An analytic solution for a uniaxial spherical resonator is presented using the method of Debye potentials. This serves as a starting point for the calculation of whispering gallery modes (WGMs) in such a resonator. Suitable approximations for the radial functions are discussed in order to best characterize WGMs. The characteristic equation and its asymptotic expansion for the anisotropic case is also discussed, and an analytic formula with a precision of the order O[{nu}{sup -1}] is also given. Our careful treatment of both boundary conditions and asymptotic expansions makes the present work a particularly suitable platform for a quantum theory of whispering gallery resonators.

  5. Whispering Gallery Mode Resonators as Optical Reference Cavities

    NASA Technical Reports Server (NTRS)

    Baumgartel, Lukas; Thompson, Rob; Strekalov, Dmitry; Grudinin, Ivan; Yu, Nan

    2011-01-01

    Highly stabilized lasers are an increasingly valuable tool for metrology. For many applications, however, existing Fabry Perot systems are too bulky and cumbersome. We are investigating the use of miniature monolithic whispering gallery mode resonators as reference cavities for laser stabilization. We seek to exploit the benefit of small size and vibration resistance by suppressing thermally induced frequency fluctuations. We have theoretically investigated the viability of using a thin-film coating to achieve temperature compensation. We have experimentally investigated an active temperature stabilization scheme based on birefringence in a crystalline resonator. We also report progress of laser locking to the resonators.

  6. Whispering-Gallery Mode Resonators for Detecting Cancer

    PubMed Central

    Pongruengkiat, Weeratouch; Pechprasarn, Suejit

    2017-01-01

    Optical resonators are sensors well known for their high sensitivity and fast response time. These sensors have a wide range of applications, including in the biomedical fields, and cancer detection is one such promising application. Sensor diagnosis currently has many limitations, such as being expensive, highly invasive, and time-consuming. New developments are welcomed to overcome these limitations. Optical resonators have high sensitivity, which enable medical testing to detect disease in the early stage. Herein, we describe the principle of whispering-gallery mode and ring optical resonators. We also add to the knowledge of cancer biomarker diagnosis, where we discuss the application of optical resonators for specific biomarkers. Lastly, we discuss advancements in optical resonators for detecting cancer in terms of their ability to detect small amounts of cancer biomarkers. PMID:28902169

  7. An Investigation of Lateral Modes in FBAR Resonators.

    PubMed

    Jamneala, Tiberiu; Bradley, Paul; Shirakawa, Alexandre; Thalhammer, Robert; Ruby, Richard

    2016-02-24

    Using first principles and the constitutive equations for a piezoelectric, we solve the 2D acoustic wave inside a single, infinite, piezoelectric membrane in order to study the dispersion of Thin Film Bulk Acoustic Resonator (FBAR) lateral modes, with and without infinitely-thin electrodes. The acoustic eigenfunction is a dual wave, composed of longitudinal and shear components, able to satisfy the 2D acoustic boundary conditions at the vacuum interfaces. For the single piezoelectric slab we obtain analytical expressions of the dispersion for frequencies near the longitudinal resonant frequency (Fs) of the resonator. These expressions are more useful for the understanding of dispersion in FBARs and more elegant than numerical methods like Finite Element Modeling (FEM) and various matrix methods. We additionally find that the interaction between the resonator's electrodes and the acoustic wave modifies the lateral mode dispersion when compared to the case with no electrodes. When correctly accounting for these interactions the dispersion zero is placed clearly at Fs, unlike what is calculated from a 2D model without electrodes where the dispersion zero is placed at Fp. This is important since all experimental evidence of measures FBAR resonators shows that the dispersion zero is at Fs. Furthermore, we introduce an electrical current flow model for the propagating acoustic wave inside the electroded piezoelectric and based on this model we can discuss an electrode-loss mechanism for FBAR lateral modes which depends on dispersion. From our model it results that lateral modes with real kx have higher electrode dissipation if they are closer to the resonant frequency. This is consistent with the typical behavior of measured FBAR filters where the maximum lateral mode damage on the insertion loss takes place for frequencies immediately below Fs.

  8. Performance and operation of advanced superconducting electron cyclotron resonance ion source SECRAL at 24 GHz

    SciTech Connect

    Zhao, H. W.; Zhang, X. Z.; Feng, Y. C.; Guo, J. W.; Li, J. Y.; Guo, X. H.; Sha, S.; Sun, L. T.; Xie, D. Z.; Lu, W.; Cao, Y.

    2012-02-15

    SECRAL (superconducting ECR ion source with advanced design in Lanzhou) ion source has been in routine operation for Heavy Ion Research Facility in Lanzhou (HIRFL) accelerator complex since May 2007. To further enhance the SECRAL performance in order to satisfy the increasing demand for intensive highly charged ion beams, 3-5 kW high power 24 GHz single frequency and 24 GHz +18 GHz double frequency with an aluminum plasma chamber were tested, and some exciting results were produced with quite a few new record highly charged ion beam intensities, such as {sup 129}Xe{sup 35+} of 64 e{mu}A, {sup 129}Xe{sup 42+} of 3 e{mu}A, {sup 209}Bi{sup 41+} of 50 e{mu}A, {sup 209}Bi{sup 50+} of 4.3 e{mu}A and {sup 209}Bi{sup 54+} of 0.2 e{mu}A. In most cases SECRAL is operated at 18 GHz to deliver highly charged heavy ion beams for the HIRFL accelerator, only for those very high charge states and very heavy ion beams such as {sup 209}Bi{sup 36+} and {sup 209}Bi{sup 41+}, SECRAL has been operated at 24 GHz. The total operation beam time provided by SECRAL up to July 2011 has exceeded 7720 hours. In this paper, the latest performance, development, and operation status of SECRAL ion source are presented. The latest results and reliable long-term operation for the HIRFL accelerator have demonstrated that SECRAL performance for production of highly charged heavy ion beams remains improving at higher RF power with optimized tuning.

  9. Sensitivity of a label-free guided-mode resonant optical biosensor with different modes.

    PubMed

    Wang, Qi; Zhang, Dawei; Yang, Huiyin; Tao, Chunxian; Huang, Yuanshen; Zhuang, Songlin; Mei, Ting

    2012-01-01

    Sensitivity is a key factor in the performance of a sensor. To achieve maximum guided-mode resonant optical biosensor sensitivity, a comparison of biosensor sensitivity for Transverse Electric (TE) and Transverse Magnetic (TM) modes based on the distribution of electric fields is presented in this article. A label-free guided-mode resonant optical biosensor is designed using the quarter-wave anti-reflection method to reflect only a narrow band of wavelengths modulated by the adsorption of a biochemical material on the sensor surface at the reflected frequency. With the distribution of electric fields simulated according to the Rigorous Coupled Wave Analysis (RCWA) theory, it is found that the full width at half maximum of the TM mode is (≈ 4 nm) narrower than that of the TE mode (≈ 20 nm), and the surface sensitivity of the TE mode incident light is three times that of the TM mode. It is proposed in this article that the light mode plays an important role in the sensitivity of guided-mode resonant biosensors.

  10. Nonlinear coupling of flexural mode and extensional bulk mode in micromechanical resonators

    NASA Astrophysics Data System (ADS)

    Zhang, Tianyi; Ren, Juan; Wei, Xueyong; Jiang, Zhuangde; Huan, Ronghua

    2016-11-01

    The effect of coupling between the extensional bulk mode and the flexural mode of a cantilever beam resonator has been experimentally studied by exciting the two modes simultaneously. The modal frequency shift of linear extensional bulk mode shows a quadratic relationship with the square of flexural mode's amplitude displacement, and a frequency shift up to 1492 Hz is observed when the flexural mode is driven by a AC signal Vac of 3 V and a DC bias of 30 V. The flexural mode shows a Duffing-like behavior with a softening nonlinearity and its frequency shift is influenced not only by its own nonlinear amplitude-frequency effect but also the extensional mode's amplitude as predicted. The nonlinear coupling coefficient is found to be about two orders of magnitude larger than the softening nonlinearity.

  11. Under-Coupling Whispering Gallery Mode Resonator Applied to Resonant Micro-Optic Gyroscope

    PubMed Central

    Qian, Kun; Tang, Jun; Guo, Hao; Liu, Wenyao; Liu, Jun; Xue, Chenyang; Zheng, Yongqiu; Zhang, Chengfei

    2017-01-01

    As an important sensing element, the whispering gallery mode resonator (WGMR) parameters seriously affect the resonant micro-optic gyroscope (RMOG) performance. This work proposes an under-coupling resonator to improve the resonator’s Q value and to optimize the coupling coefficient to maximize the RMOG’s sensitivity. GeO2-doped silica waveguide-type resonators with different coupling coefficients were simulated, designed, fabricated and tested. An under-coupling ring resonator with a quality factor of 10 million is reported. The RMOG system was built based on this resonator and the scale factor was tested on a uniaxial high-precision rotating platform. Experimental results show that this resonator could improve the RMOG sensitivity by five times. PMID:28067824

  12. Superradiant modes in Fibonacci quantum wells under resonant conditions

    NASA Astrophysics Data System (ADS)

    Chang, C. H.; Tsao, C. W.; Hsueh, W. J.

    2014-11-01

    It is first presented that superradiant modes exist in Fibonacci quantum wells within the exact regions that are obtained using the gap map diagram, rather than the traditional resonant Bragg condition. The results show that three limited regions are derived from the diagram, which correspond to bandgaps with widths that differ from each other. The regions in which the superradiant modes do not occur are also defined clearly. Moreover, the proposed method can be used to determine whether superradiant modes occur in multiple quantum wells that have non-periodical arrangements, including quasiperiodic sequences and correlated disorder sequences.

  13. Polarization characteristics of the Schumann resonance modes in Tomsk

    NASA Astrophysics Data System (ADS)

    Kolesnik, S. A.; Kolmakov, A. A.; Nedosekov, D. A.

    2015-11-01

    The article describes the experimentally determined distribution of ellipticity coefficient for the first three modes of the Schumann resonances (SR) for different seasons in 2014. Established the presence of seasonal variation of the frequency of occurrence for different types of polarization of the first three modes SR. It is shown that the frequency of occurrence of elliptical polarization for different modes of SR is about 70-80%. Circular polarization - a very rare event, the frequency of its occurrence is less than 1% for every season of the year.

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

    PubMed Central

    Hajjaj, Amal Z.; Hafiz, Md Abdullah; Younis, Mohammad I.

    2017-01-01

    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. PMID:28134329

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

    NASA Astrophysics Data System (ADS)

    Hajjaj, Amal Z.; Hafiz, Md Abdullah; Younis, Mohammad I.

    2017-01-01

    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.

  16. HIGH POWER TEST OF A 3.9 GHZ 5-CELL DEFLECTING-MODE CAVITY IN A CRYOGENIC OPERATION

    SciTech Connect

    Shin, Young-Min; Church, Michael

    2013-11-24

    A 3.9 GHz deflecting mode (S, TM110) cavity has been long used for six-dimensional phase-space beam manipulation tests [1-5] at the A0 Photo-Injector Lab (16 MeV) in Fermilab and their extended applications with vacuum cryomodules are currently planned at the Advanced Superconducting Test Accelerator (ASTA) user facility (> 50 MeV). Despite the successful test results, the cavity, however, demonstrated limited RF performance during liquid nitrogen (LN2) ambient operation that was inferior to theoretical prediction. We have been performing full analysis of the designed cavity by analytic calculation and comprehensive system simulation analysis to solve complex thermodynamics and mechanical stresses. The re-assembled cryomodule is currently under the test with a 50 kW klystron at the Fermilab A0 beamline, which will benchmark the modeling analysis. The test result will be used to design vacuum cryomodules for the 3.9 GHz deflecting mode cavity that will be employed at the ASTA facility for beam diagnostics and phase-space control.

  17. Transforming Fabry-Pérot resonances into a Tamm mode

    NASA Astrophysics Data System (ADS)

    Durach, Maxim; Rusina, Anastasia

    2012-12-01

    We propose an optical structure composed of two metal nanolayers enclosing a distributed Bragg reflector (DBR) mirror. The structure is an open photonic system whose bound modes are coupled to external radiation. We apply the special theoretical treatment based on inversion symmetry of the structure to classify its resonances. We show that the structure supports resonances transitional between Fabry-Pérot modes and Tamm plasmons. When the dielectric contrast of the DBR is removed these modes are a pair of conventional Fabry-Pérot resonances. They spectrally merge into a Tamm mode at high contrast. The optical properties of the structure in the frequency range of the DBR stop band, including highly beneficial 50% transmittivity through thick structures with sub-skin-depth metal films, are determined by the hybrid quasinormal modes of the open nonconservative structure under consideration. The results can find a broad range of applications in photonics and optoelectronics, including the possibility of coherent control over optical fields in the class of structures similar to the one proposed here.

  18. Scissors mode of Gd nuclei studied from resonance neutron capture

    SciTech Connect

    Kroll, J.; Baramsai, B.; Becker, J. A.; and others

    2012-10-20

    Spectra of {gamma} rays following the neutron capture at isolated resonances of stable Gd nuclei were measured. The objectives were to get new information on photon strength of {sup 153,155-159}Gd with emphasis on the role of the M1 scissors-mode vibration. An analysis of the data obtained clearly indicates that the scissors mode is coupled not only to the ground state, but also to all excited levels of the nuclei studied. The specificity of our approach ensures unbiasedness in estimating the sumed scissors-mode strength {Sigma}B(M1){up_arrow}, even for odd product nuclei, for which conventional nuclear resonance fluorescence measurements yield only limited information. Our analysis indicates that for these nuclei the sum {Sigma}B(M1){up_arrow} increases with A and for {sup 157,159}Gd it is significantly higher compared to {sup 156,158}Gd.

  19. H- extraction from electron-cyclotron-resonance-driven multicusp volume source operated in pulsed mode

    NASA Astrophysics Data System (ADS)

    Svarnas, P.; Bacal, M.; Auvray, P.; Béchu, S.; Pelletier, J.

    2006-03-01

    H2 microwave (2.45GHz) pulsed plasma is produced from seven elementary electron cyclotron resonance sources installed into the magnetic multipole chamber "Camembert III" (École Polytechnique—Palaiseau) from which H- extraction takes place. The negative-ion and electron extracted currents are studied through electrical measurements and the plasma parameters by means of electrostatic probe under various experimental conditions. The role of the plasma electrode bias and the discharge duty cycle in the extraction process is emphasized. The gas breakdown at the beginning of every pulse gives rise to variations of the plasma characteristic parameters in comparison with those established at the later time of the pulse, where the electron temperature, the plasma potential, and the floating potential converge to the values obtained for a continuous plasma. The electron density is significantly enhanced in the pulsed mode.

  20. Characterization of the resonant electromagnetic mode in helicon discharges

    NASA Astrophysics Data System (ADS)

    Panevsky, Martin Ivanov

    2003-10-01

    This dissertation is motivated by a collaboration between the University of Texas at Austin and NASA on the VASIMR project. The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) is an effort to create a plasma-based thruster. The proposed thruster uses a helicon plasma discharge as its plasma source. An ICRH heating mechanism is then employed to impart energy into the plasma. A magnetic nozzle exhausts the plasma converting the ion gyromotion into superalfvenic longitudinal motion, thus creating thrust. The physics behind the helicon plasma source is an area of active experimental and theoretical research and we are presenting experimental results which cast the problem of helicon plasma in a new light. Our experimental results point to the existence of a resonant electromagnetic mode in the helicon plasma. The data suggests that this mode is universal in the helicon discharge and can be excited over a wide range of frequencies. The resonant frequency is slightly lower than the driving frequency in steady-state. The radial component of the perturbed magnetic field of the resonance mode is peaked at a radius r* where the radial density gradient of the plasma has a maximum. The energy damping rate of the resonant mode is relatively low and cannot deposit the mode energy into the plasma in a single pass. The experimental data also shows that the resonant electromagnetic wave is responsible for depositing most of the available rf energy into the plasma. This supports the central conclusion of a new theory created by B. Breizman and A. Arefiev which predicts that the plasma density gradient forms a potential well which traps the electromagnetic energy. In broader terms, the trapping of the wave in a cavity formed by the density gradients of the plasma both radially and axially provides an explanation to the central dilemma of helicon plasmas: the seeming contradiction between the measured low damping rate of the wave and the measured short damping length. The

  1. Multiple magnetic mode-based Fano resonance in split-ring resonator/disk nanocavities.

    PubMed

    Zhang, Qing; Wen, Xinglin; Li, Guangyuan; Ruan, Qifeng; Wang, Jianfang; Xiong, Qihua

    2013-12-23

    Plasmonic Fano resonance, enabled by the weak interaction between a bright super-radiant and a subradiant resonance mode, not only is fundamentally interesting, but also exhibits potential applications ranging from extraordinary optical transmission to biosensing. Here, we demonstrate strong Fano resonances in split-ring resonators/disk (SRR/D) nanocavities. The high-order magnetic modes are observed in SRRs by polarization-resolved transmission spectroscopy. When a disk is centered within the SRRs, multiple high-order magnetic modes are coupled to a broad electric dipole mode of SRR/D, leading to significant Fano resonance spectral features in near-IR regime. The strength and line shape of the Fano resonances are tuned through varying the SRR split-angle and interparticle distance between SRR and disk. Finite-difference-time-domain (FDTD) simulations are conducted to understand the coupling mechanism, and the results show good agreement with experimental data. Furthermore, the coupled structure gives a sensitivity of ∼282 nm/RIU with a figure of merit ∼4.

  2. The effect of magnetopause motion on fast mode resonance

    NASA Astrophysics Data System (ADS)

    Hartinger, M. D.; Welling, D.; Viall, N. M.; Moldwin, M. B.; Ridley, A.

    2014-10-01

    The Earth's magnetosphere supports several types of ultralow frequency (ULF) waves. These include fast mode resonance (FMR): cavity modes, waveguide modes, and tunneling modes/virtual resonance. The magnetopause, often treated as the outer boundary for cavity/waveguide modes in the dayside magnetosphere, is not stationary. A rapidly changing outer boundary condition—e.g., due to rapid magnetopause motion—is not favorable for FMR generation and may explain the sparseness of FMR observations in the outer magnetosphere. We examine how magnetopause motion affects the dayside magnetosphere's ability to sustain FMR with idealized Space Weather Modeling Framework (SWMF) simulations using the BATS-R-US global magnetohydrodynamic (MHD) code coupled with the Ridley Ionosphere Model (RIM). We present observations of FMR in BATS-R-US, reproducing results from other global MHD codes. We further show that FMR is present for a wide range of solar wind conditions, even during periods with large and rapid magnetopause displacements. We compare our simulation results to FMR observations in the dayside magnetosphere, finding that FMR occurrence does not depend on solar wind dynamic pressure, which can be used as a proxy for dynamic pressure fluctuations and magnetopause perturbations. Our results demonstrate that other explanations besides a nonstationary magnetopause—such as the inability to detect FMR in the presence of other ULF wave modes with large amplitudes—are required to explain the rarity of FMR observations in the outer magnetosphere.

  3. Structure, crystallization and dielectric resonances in 2-13 GHz of waste-derived glass-ceramic

    NASA Astrophysics Data System (ADS)

    Yao, Rui; Liao, SongYi; Chen, XiaoYu; Wang, GuangRong; Zheng, Feng

    2016-12-01

    Structure, kinetics of crystallization, and dielectric resonances of waste-derived glass-ceramic prepared via quench-heating route were studied as a function of dosage of iron ore tailing (IOT) within 20-40 wt% using X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and vector network analyzer (VNA) measurements. The glass-ceramic mainly consisted of ferrite crystals embedded in borosilicate glass matrix. Crystallization kinetics and morphologies of ferrite crystals as well as coordination transformation of boron between [BO4] and [BO3] in glass network were adjustable by changing the amount of IOT. Dielectric resonances in 6-13 GHz were found to be dominated by oscillations of Ca2+ cations in glass network with [SiO4] units on their neighboring sites. Ni2+ ions made a small contribution to those resonances. Diopside formed when IOT exceeded 35 wt%, which led to weakening of the resonances.

  4. Investigations of 2.9-GHz Resonant Microwave-Sensitive Ag/MgO/Ge/Ag Tunneling Diodes

    NASA Astrophysics Data System (ADS)

    Qasrawi, A. F.; Khanfar, H. K.

    2013-12-01

    In this work, a resonant microwave-sensitive tunneling diode has been designed and investigated. The device, which is composed of a magnesium oxide (MgO) layer on an amorphous germanium (Ge) thin film, was characterized by means of temperature-dependent current ( I)-voltage ( V), room-temperature differential resistance ( R)-voltage, and capacitance ( C)-voltage characteristics. The device resonating signal was also tested and evaluated at 2.9 GHz. The I- V curves reflected weak temperature dependence and a wide tunneling region with peak-to-valley current ratio of ˜1.1. The negative differential resistance region shifts toward lower biasing voltages as temperature increases. The true operational limit of the device was determined as 350 K. A novel response of the measured R- V and C- V to the incident alternating-current (ac) signal was observed at 300 K. Particularly, the response to a 100-MHz signal power ranging from the standard Bluetooth limit to the maximum output power of third-generation mobile phones reflects a wide range of tunability with discrete switching property at particular power limits. In addition, when the tunnel device was implanted as an amplifier for a 2.90-GHz resonating signal of the power of wireless local-area network (LAN) levels, signal gain of 80% with signal quality factor of 4.6 × 104 was registered. These remarkable properties make devices based on MgO-Ge interfaces suitable as electronic circuit elements for microwave applications, bias- and time-dependent electronic switches, and central processing unit (CPU) clocks.

  5. Towards athermal organic-inorganic guided mode resonance filters.

    PubMed

    Saleem, M R; Stenberg, P; Alasaarela, T; Silfsten, P; Khan, M B; Honkanen, S; Turunen, J

    2011-11-21

    We demonstrate guided-mode resonance filters featuring an amorphous TiO(2) layer fabricated by atomic layer deposition on a polymeric substrate. The thermal properties of such filters are studied in detail by taking into account both thermal expansion of the structure and thermo-optic coefficients of the materials. We show both theoretically and experimentally that these two effects partially compensate for each other, leading to nearly athermal devices. The wavelength shift of the resonance reflectance peak (< 1 nm) is a small fraction of the peak width (~11 nm) up to temperatures exceeding the room temperature by tens of degrees centigrade.

  6. Excitation of Resonant Helioseimic Modes by Solar Flares

    NASA Astrophysics Data System (ADS)

    Leibacher, John William; Baudin, Frédéric; Rabello Soares, Maria Cristina

    2015-04-01

    Flares are known to excite propagating sound waves in the solar atmosphere, and Maurya et al. (2009), using a local analysis (ring diagrams) of the 2003 Halloween flare, showed that they excite resonant p-modes as well. We confirm and extend here these results by: applying the same analysis to other locations on the Sun at the time of the Halloween flare, analyzing other events also showing a signature of p-mode excitation, looking in detail at the results of the ring diagrams analysis in terms of noise fitting and the center-to-limb variation of ring-diagram power.

  7. Excitation of Resonant Helioseimic Modes by Solar Flares.

    NASA Astrophysics Data System (ADS)

    Leibacher, John W.; Baudin, Frédéric; Rabello Soares,, Maria Cristina

    2015-08-01

    Flares are known to excite propagating sound waves in the solar atmosphere, and Maurya et al. (2009), using a local analysis (ring diagrams) of the 2003 Halloween flare, showed that they excite resonant p-modes as well. We confirm and extend here these results by:-applying the same analysis to other locations on the Sun at the time of the Halloween flare-analyzing other events also showing a signature of p-mode excitation-looking in detail at the results of the ring diagrams analysis in terms of noise fitting and the center-to-limb variation of ring-diagram power.

  8. Development of a high-temperature oven for the 28 GHz electron cyclotron resonance ion source

    SciTech Connect

    Ohnishi, J. Higurashi, Y.; Kidera, M.; Ozeki, K.; Nakagawa, T.

    2014-02-15

    We have been developing the 28 GHz ECR ion source in order to accelerate high-intensity uranium beams at the RIKEN RI-beam Factory. Although we have generated U{sup 35+} beams by the sputtering method thus far, we began developing a high-temperature oven with the aim of increasing and stabilizing the beams. Because the oven method uses UO{sub 2}, a crucible must be heated to a temperature higher than 2000 °C to supply an appropriate amount of UO{sub 2} vapor to the ECR plasma. Our high-temperature oven uses a tungsten crucible joule-heated with DC current of approximately 450 A. Its inside dimensions are ϕ11 mm × 13.5 mm. Since the crucible is placed in a magnetic field of approximately 3 T, it is subject to a magnetic force of approximately 40 N. Therefore, we used ANSYS to carefully design the crucible, which was manufactured by machining a tungsten rod. We could raise the oven up to 1900 °C in the first off-line test. Subsequently, UO{sub 2} was loaded into the crucible, and the oven was installed in the 28 GHz ECR ion source and was tested. As a result, a U{sup 35+} beam current of 150 μA was extracted successfully at a RF power of approximately 3 kW.

  9. Spaser quenching by off-resonant plasmon modes

    NASA Astrophysics Data System (ADS)

    Petrosyan, L. S.; Shahbazyan, T. V.

    2017-08-01

    We study the effect of off-resonant plasmon modes on spaser threshold in nanoparticle-based spasers. We develop an analytical semiclassical model and derive spaser threshold condition accounting for gain coupling to higher-order plasmons. We show that such a coupling originates from inhomogeneity of gain distribution near the metal surface and leads to an upward shift of spaser frequency and population inversion threshold. This effect is similar, albeit significantly weaker, to quenching of plasmon-enhanced fluorescence near metal nanostructures due to excitation of off-resonant modes with wide spectral band. We also show that spaser quenching is suppressed for high gain concentrations and establish a simple criterion for quenching onset, which we support by numerical calculations for spherical geometry.

  10. Scissors Mode of 162 Dy Studied from Resonance Neutron Capture

    DOE PAGES

    Baramsai, B.; Bečvář, F.; Bredeweg, T. A.; ...

    2015-05-28

    Multi-step cascade γ-ray spectra from the neutron capture at isolated resonances of 161Dy nucleus were measured at the LANSCE/DANCE time-of-flight facility in Los Alamos National Laboratory. The objectives of this experiment were to confirm and possibly extend the spin assignment of s-wave neutron resonances and get new information on photon strength functions with emphasis on the role of the M1 scissors mode vibration. The preliminary results show that the scissors mode plays a significant role in all transitions between accessible states of the studied nucleus. The photon strength functions describing well our data are compared to results from 3He-induced reactions,more » (n,γ) experiments on Gd isotopes, and (γ,γ’) reactions.« less

  11. Active flat optics using a guided mode resonance.

    PubMed

    Kim, Soo Jin; Brongersma, Mark L

    2017-01-01

    Dynamically-controlled flat optics relies on achieving active and effective control over light-matter interaction in ultrathin layers. A variety of metasurface designs have achieved efficient amplitude and phase modulation. Particularly, noteworthy progress has been made with the incorporation of newly emerging electro-optical materials into such metasurfaces, including graphene, phase change materials, and transparent conductive oxides. In this Letter, we demonstrate dynamic light-matter interaction in a silicon-based subwavelength grating that supports a guided mode resonance. By overcoating the grating with indium tin oxide as an electrically tunable material, its reflectance can be tuned from 4% to 86%. Guided mode resonances naturally afford higher optical quality factors than the optical antennas used in the construction of metasurfaces. As such, they facilitate more effective control over the flow of light within the same layer thickness.

  12. Analysis of modes in an unstable strip laser resonator

    NASA Astrophysics Data System (ADS)

    Rowley, J. E.

    1980-12-01

    The mode eigenvalue equation for an unstable strip laser resonator is developed from scalar diffraction theory. The field distributions are expressed as a series and the integral is then evaluated using a first order approximation to the method of stationary phase. The resulting approximate closed form is rearranged to form an eigenvalue polynomial, the roots of which are the mode eigenvalues. Eigenfunction expressions are then developed using second order approximation to the method of stationary phase. Modifications to these expressions are then made to account for the presence of uniform gain in the resonator. The results of a computer program using the derived expressions are presented. Comparisons to previously published results are made for the bare cavity case, and results for the loaded cavity case follow.

  13. Multistable internal resonance in electroelastic crystals with nonlinearly coupled modes

    NASA Astrophysics Data System (ADS)

    Kirkendall, Christopher R.; Kwon, Jae W.

    2016-03-01

    Nonlinear modal interactions have recently become the focus of intense research in micro- and nanoscale resonators for their use to improve oscillator performance and probe the frontiers of fundamental physics. However, our understanding of modal coupling is largely restricted to clamped-clamped beams, and lacking in systems with both geometric and material nonlinearities. Here we report multistable energy transfer between internally resonant modes of an electroelastic crystal plate and use a mixed analytical-numerical approach to provide new insight into these complex interactions. Our results reveal a rich bifurcation structure marked by nested regions of multistability. Even the simple case of two coupled modes generates a host of topologically distinct dynamics over the parameter space, ranging from the usual Duffing bistability to complex multistable behaviour and quasiperiodic motion.

  14. Multistable internal resonance in electroelastic crystals with nonlinearly coupled modes

    PubMed Central

    Kirkendall, Christopher R.; Kwon, Jae W.

    2016-01-01

    Nonlinear modal interactions have recently become the focus of intense research in micro- and nanoscale resonators for their use to improve oscillator performance and probe the frontiers of fundamental physics. However, our understanding of modal coupling is largely restricted to clamped-clamped beams, and lacking in systems with both geometric and material nonlinearities. Here we report multistable energy transfer between internally resonant modes of an electroelastic crystal plate and use a mixed analytical-numerical approach to provide new insight into these complex interactions. Our results reveal a rich bifurcation structure marked by nested regions of multistability. Even the simple case of two coupled modes generates a host of topologically distinct dynamics over the parameter space, ranging from the usual Duffing bistability to complex multistable behaviour and quasiperiodic motion. PMID:26961749

  15. Scissors Mode of 162Dy Studied from Resonance Neutron Capture

    NASA Astrophysics Data System (ADS)

    Baramsai, B.; Bečvář, F.; Bredeweg, T. A.; Haight, R. C.; Jandel, M.; Kroll, J.; Krtička, M.; Mitchell, G. E.; O'Donnell, J. M.; Rundberg, R. S.; Ullmann, J. L.; Valenta, S.; Wilhelmy, J. B.

    2015-05-01

    Multi-step cascade γ-ray spectra from the neutron capture at isolated resonances of 161Dy nucleus were measured at the LANSCE/DANCE time-of-flight facility in Los Alamos National Laboratory. The objectives of this experiment were to confirm and possibly extend the spin assignment of s-wave neutron resonances and get new information on photon strength functions with emphasis on the role of the M1 scissors mode vibration. The preliminary results show that the scissors mode plays a significant role in all transitions between accessible states of the studied nucleus. The photon strength functions describing well our data are compared to results from 3He-induced reactions, (n,γ) experiments on Gd isotopes, and (γ,γ') reactions.

  16. 2 GHz passively harmonic mode-locked fiber laser by a microfiber-based topological insulator saturable absorber.

    PubMed

    Luo, Zhi-Chao; Liu, Meng; Liu, Hao; Zheng, Xu-Wu; Luo, Ai-Ping; Zhao, Chu-Jun; Zhang, Han; Wen, Shuang-Chun; Xu, Wen-Cheng

    2013-12-15

    We report on the generation of passive harmonic mode locking of a fiber laser using a microfiber-based topological insulator (TI) Bi(2)Te(3) saturable absorber (SA). The optical deposition method was employed to fabricate the microfiber-based TISA. By virtue of the excellent nonlinear optical property of the proposed TISA, the fiber laser could operate at the pulse repetition rate of 2.04 GHz under a pump power of 126 mW, corresponding to the 418th harmonic of fundamental repetition frequency. The results demonstrate that the microfiber-based TI photonic device can operate as both the high nonlinear optical component and the SA in fiber lasers, and could also find other applications in the related fields of photonics.

  17. 225-255-GHz InP DHBT Frequency Tripler MMIC Using Complementary Split-Ring Resonator

    NASA Astrophysics Data System (ADS)

    Li, Xiao; Zhang, Yong; Li, Oupeng; Sun, Yan; Lu, Haiyan; Cheng, Wei; Xu, Ruimin

    2017-02-01

    In this paper, a novel design of frequency tripler monolithic microwave integrated circuit (MMIC) using complementary split-ring resonator (CSRR) is proposed based on 0.5-μm InP DHBT process. The CSRR-loaded microstrip structure is integrated in the tripler as a part of impedance matching network to suppress the fundamental harmonic, and another frequency tripler based on conventional band-pass filter is presented for comparison. The frequency tripler based on CSRR-loaded microstrip generates an output power between -8 and -4 dBm from 228 to 255 GHz when the input power is 6 dBm. The suppression of fundamental harmonic is better than 20 dBc at 77-82 GHz input frequency within only 0.15 × 0.15 mm2 chip area of the CSRR structure on the ground layer. Compared with the frequency tripler based on band-pass filter, the tripler using CSRR-loaded microstrip obtains a similar suppression level of unwanted harmonics and higher conversion gain within a much smaller chip area. To our best knowledge, it is the first time that CSRR is used for harmonic suppression of frequency multiplier at such high frequency band.

  18. Mode converter for electron cyclotron resonance heating of toroidal plasmas

    SciTech Connect

    Motley, R.W.; Hsuan, H.; Glanz, J.

    1980-09-01

    A method is proposed for improving the efficiency of cyclotron resonance heating of a toroidal plasma by ordinary mode radiation from the outside of the torus. Radiation not absorbed in the first pass is reflected from the inside of the torus by a corrugated surface which rotates the polarization by 90/sup 0/, so that a secondary source of extraordinary waves is created in the high field, accessible region of the plasma.

  19. Are Resonant Helioseimic Modes Excited by Solar Flares?

    NASA Astrophysics Data System (ADS)

    Leibacher, John W.; Baudin, Frédéric; Rabello Soares, Maria Cristina

    2016-05-01

    We critically examine reports that flares have been observed to excite resonant p-modes by:-looking in detail at the results of the ring-diagram analysis in terms of duty cycle and center-to-limb variation of ring-diagram power.-applying the same analysis to the Halloween flare using GONG and MDI data.-assessing the stability in terms of oscillation power of both instruments.

  20. Numerical modelling of thermal effects in rats due to high-field magnetic resonance imaging (0.5 1 GHz)

    NASA Astrophysics Data System (ADS)

    Trakic, Adnan; Crozier, Stuart; Liu, Feng

    2004-12-01

    A finite-difference time-domain (FDTD) thermal model has been developed to compute the temperature elevation in the Sprague Dawley rat due to electromagnetic energy deposition in high-field magnetic resonance imaging (MRI). The field strengths examined ranged from 11.75-23.5 T (corresponding to 1H resonances of 0.5-1 GHz) and an N-stub birdcage resonator was used to both transmit radio-frequency energy and receive the MRI signals. With an in-plane resolution of 1.95 mm, the inhomogeneous rat phantom forms a segmented model of 12 different tissue types, each having its electrical and thermal parameters assigned. The steady-state temperature distribution was calculated using a Pennes 'bioheat' approach. The numerical algorithm used to calculate the induced temperature distribution has been successfully validated against analytical solutions in the form of simplified spherical models with electrical and thermal properties of rat muscle. As well as assisting with the design of MRI experiments and apparatus, the numerical procedures developed in this study could help in future research and design of tumour-treating hyperthermia applicators to be used on rats in vivo.

  1. Numerical modelling of thermal effects in rats due to high-field magnetic resonance imaging (0.5-1 GHZ).

    PubMed

    Trakic, Adnan; Crozier, Stuart; Liu, Feng

    2004-12-21

    A finite-difference time-domain (FDTD) thermal model has been developed to compute the temperature elevation in the Sprague Dawley rat due to electromagnetic energy deposition in high-field magnetic resonance imaging (MRI). The field strengths examined ranged from 11.75-23.5 T (corresponding to 1H resonances of 0.5-1 GHz) and an N-stub birdcage resonator was used to both transmit radio-frequency energy and receive the MRI signals. With an in-plane resolution of 1.95 mm, the inhomogeneous rat phantom forms a segmented model of 12 different tissue types, each having its electrical and thermal parameters assigned. The steady-state temperature distribution was calculated using a Pennes 'bioheat' approach. The numerical algorithm used to calculate the induced temperature distribution has been successfully validated against analytical solutions in the form of simplified spherical models with electrical and thermal properties of rat muscle. As well as assisting with the design of MRI experiments and apparatus, the numerical procedures developed in this study could help in future research and design of tumour-treating hyperthermia applicators to be used on rats in vivo.

  2. Measurement of the resonance shift in the radar backscattering cross section of thick stainless steel fibers at 35 GHz

    NASA Astrophysics Data System (ADS)

    Alyones, Sharhabeel; Bruce, Charles

    2007-03-01

    Measurements of the radar backscattering cross section of stainless steel fibers with low length-to-diameter ratio (thick fibers) had been done at 35 GHz. The intention was to confirm the resonance shift in length predicted by a numerical solution of the general problem of electromagnetic scattering and absorption by finite conducting wires [1]. The numerical methods solves the generalized form of the Pocklington equation, which is valid for both thin and thick fibers. Single particle radar backscattering measurement system was used and the resonance shift had been confirmed for four sets of aspect ratios. The position of the first resonance is shifted to shorter lengths in comparison with the previous analytical solution of the problem by P. Watermann and J. Pedersen [2]. [1] Sharhabeel Alyones, Charles W. Bruce, and Andrei Buin, `` Numerical methods for solving the problem of electromagnetic scattering by a finite thin conducting wire'', accepted for publication in IEEE. Trans. Antennas and Propag. [2] P. C. Waterman, ``Scattering, absorption and extinction by thin fibers,'' Accepted for publication in J. Opt. Soc. A.

  3. Tearing mode velocity braking due to resonant magnetic perturbations

    NASA Astrophysics Data System (ADS)

    Frassinetti, L.; Menmuir, S.; Olofsson, K. E. J.; Brunsell, P. R.; Drake, J. R.

    2012-10-01

    The effect of resonant magnetic perturbations (RMPs) on the tearing mode (TM) velocity is studied in EXTRAP T2R. Experimental results show that the RMP produces TM braking until a new steady velocity or wall locking is reached. The braking is initially localized at the TM resonance and then spreads to the other TMs and to the rest of the plasma producing a global velocity reduction via the viscous torque. The process has been used to experimentally estimate the kinematic viscosity profile, in the range 2-40 m2 s-1, and the electromagnetic torque produced by the RMP, which is strongly localized at the TM resonance. Experimental results are then compared with a theoretical model which gives a reasonable qualitative explanation of the entire process.

  4. Resonant mode interactions and the bifurcation of combustion-driven acoustic oscillations in resonance tubes

    SciTech Connect

    Margolis, S.B. . Combustion Research Facility)

    1994-12-01

    Acoustic oscillations in practical combustion devices such as pulse combustors and rocket motors, whether desirable or not, are properly interpreted as combustion instabilities. A nonlinear stability analysis of the corresponding fluid motions than shows that the nonsteady behavior is governed by infinitely coupled systems of nonlinear evolution equations for the amplitudes of the classical acoustic modes. However, under certain conditions, it has been conjectured that relatively low-order truncations can give qualitatively correct physical results. In the present work, one particular model of a pulse combustor is considered, and a parameter regime in the neighborhood of a primary acoustic bifurcation where either one or a pair of purely longitudinal acoustic modes achieves a positive linear growth rate is focused upon. In the first case, it is formally shown that a decoupling occurs such that a two-mode approximation consisting of the linearly unstable mode and its first resonant harmonic completely determines the dynamics of the oscillation. In the later case, it is again demonstrated that a decoupling occurs, and although mode interactions require the retention of additional modes besides the two linearly unstable modes and their first resonant harmonics, a relatively low-order dynamical system still governs the bifurcation behavior. The presence of two linearly unstable modes is then shown to lead to more complicated dynamics, including the stable secondary bifurcation of a multiperiodic acoustic oscillation from one of the single-period primary branches.

  5. The effect of cavity tuning on oxygen beam currents of an A-ECR type 14 GHz electron cyclotron resonance ion source

    SciTech Connect

    Tarvainen, O. Orpana, J.; Kronholm, R.; Kalvas, T.; Laulainen, J.; Koivisto, H.; Izotov, I.; Skalyga, V.; Toivanen, V.

    2016-09-15

    The efficiency of the microwave-plasma coupling plays a significant role in the production of highly charged ion beams with electron cyclotron resonance ion sources (ECRISs). The coupling properties are affected by the mechanical design of the ion source plasma chamber and microwave launching system, as well as damping of the microwave electric field by the plasma. Several experiments attempting to optimize the microwave-plasma coupling characteristics by fine-tuning the frequency of the injected microwaves have been conducted with varying degrees of success. The inherent difficulty in interpretation of the frequency tuning results is that the effects of microwave coupling system and the cavity behavior of the plasma chamber cannot be separated. A preferable approach to study the effect of the cavity properties of the plasma chamber on extracted beam currents is to adjust the cavity dimensions. The results of such cavity tuning experiments conducted with the JYFL 14 GHz ECRIS are reported here. The cavity properties were adjusted by inserting a conducting tuner rod axially into the plasma chamber. The extracted beam currents of oxygen charge states O{sup 3+}–O{sup 7+} were recorded at various tuner positions and frequencies in the range of 14.00–14.15 GHz. It was observed that the tuner position affects the beam currents of high charge state ions up to several tens of percent. In particular, it was found that at some tuner position / frequency combinations the plasma exhibited “mode-hopping” between two operating regimes. The results improve the understanding of the role of plasma chamber cavity properties on ECRIS performances.

  6. The effect of cavity tuning on oxygen beam currents of an A-ECR type 14 GHz electron cyclotron resonance ion source

    NASA Astrophysics Data System (ADS)

    Tarvainen, O.; Orpana, J.; Kronholm, R.; Kalvas, T.; Laulainen, J.; Koivisto, H.; Izotov, I.; Skalyga, V.; Toivanen, V.

    2016-09-01

    The efficiency of the microwave-plasma coupling plays a significant role in the production of highly charged ion beams with electron cyclotron resonance ion sources (ECRISs). The coupling properties are affected by the mechanical design of the ion source plasma chamber and microwave launching system, as well as damping of the microwave electric field by the plasma. Several experiments attempting to optimize the microwave-plasma coupling characteristics by fine-tuning the frequency of the injected microwaves have been conducted with varying degrees of success. The inherent difficulty in interpretation of the frequency tuning results is that the effects of microwave coupling system and the cavity behavior of the plasma chamber cannot be separated. A preferable approach to study the effect of the cavity properties of the plasma chamber on extracted beam currents is to adjust the cavity dimensions. The results of such cavity tuning experiments conducted with the JYFL 14 GHz ECRIS are reported here. The cavity properties were adjusted by inserting a conducting tuner rod axially into the plasma chamber. The extracted beam currents of oxygen charge states O3+-O7+ were recorded at various tuner positions and frequencies in the range of 14.00-14.15 GHz. It was observed that the tuner position affects the beam currents of high charge state ions up to several tens of percent. In particular, it was found that at some tuner position / frequency combinations the plasma exhibited "mode-hopping" between two operating regimes. The results improve the understanding of the role of plasma chamber cavity properties on ECRIS performances.

  7. The effect of cavity tuning on oxygen beam currents of an A-ECR type 14 GHz electron cyclotron resonance ion source.

    PubMed

    Tarvainen, O; Orpana, J; Kronholm, R; Kalvas, T; Laulainen, J; Koivisto, H; Izotov, I; Skalyga, V; Toivanen, V

    2016-09-01

    The efficiency of the microwave-plasma coupling plays a significant role in the production of highly charged ion beams with electron cyclotron resonance ion sources (ECRISs). The coupling properties are affected by the mechanical design of the ion source plasma chamber and microwave launching system, as well as damping of the microwave electric field by the plasma. Several experiments attempting to optimize the microwave-plasma coupling characteristics by fine-tuning the frequency of the injected microwaves have been conducted with varying degrees of success. The inherent difficulty in interpretation of the frequency tuning results is that the effects of microwave coupling system and the cavity behavior of the plasma chamber cannot be separated. A preferable approach to study the effect of the cavity properties of the plasma chamber on extracted beam currents is to adjust the cavity dimensions. The results of such cavity tuning experiments conducted with the JYFL 14 GHz ECRIS are reported here. The cavity properties were adjusted by inserting a conducting tuner rod axially into the plasma chamber. The extracted beam currents of oxygen charge states O(3+)-O(7+) were recorded at various tuner positions and frequencies in the range of 14.00-14.15 GHz. It was observed that the tuner position affects the beam currents of high charge state ions up to several tens of percent. In particular, it was found that at some tuner position / frequency combinations the plasma exhibited "mode-hopping" between two operating regimes. The results improve the understanding of the role of plasma chamber cavity properties on ECRIS performances.

  8. Two-mode model for metal-dielectric guided-mode resonance filters.

    PubMed

    Tuambilangana, Christelle; Pardo, Fabrice; Sakat, Emilie; Bouchon, Patrick; Pelouard, Jean-Luc; Haïdar, Riad

    2015-12-14

    Symmetric metal-dielectric guided-mode resonators (GMR) can operate as infrared band-pass filters, thanks to high-transmission resonant peaks and good rejection ratio. Starting from matrix formalism, we show that the behavior of the system can be described by a two-mode model. This model reduces to a scalar formula and the GMR is described as the combination of two independent Fabry-Perot resonators. The formalism has then been applied to the case of asymmetric GMR, in order to restore the properties of the symmetric system. This result allows designing GMR-on-substrate as efficient as free-standing systems, the same high transmission maximum value and high quality factor being conserved.

  9. Coupled modes of the resonance box of the guitar.

    PubMed

    Elejabarrieta, M J; Ezcurra, A; Santamaria, C

    2002-05-01

    Vibrations of the resonance box of the guitar have been studied by means of the modal analysis technique and the finite-element method. An expert craftsman constructed the guitar box with all the structures, internal and external, characteristic of a real instrument for the experimental measurements. The boundary conditions were chosen in order to clarify the soundboard-back interaction only via the internal air coupling. The numerical model allows one to study the influence of each component on the whole box, and the contribution of the modes of the components (wooden box and its parts, and air), to the coupled modes by calculating their participation factors. The coupled modes of the guitar box are discussed taking into account both the finite-element and modal analysis results.

  10. Coupled modes of the resonance box of the guitar

    NASA Astrophysics Data System (ADS)

    Elejabarrieta, M. J.; Ezcurra, A.; SantamaríA, C.

    2002-05-01

    Vibrations of the resonance box of the guitar have been studied by means of the modal analysis technique and the finite-element method. An expert craftsman constructed the guitar box with all the structures, internal and external, characteristic of a real instrument for the experimental measurements. The boundary conditions were chosen in order to clarify the soundboard-back interaction only via the internal air coupling. The numerical model allows one to study the influence of each component on the whole box, and the contribution of the modes of the components (wooden box and its parts, and air), to the coupled modes by calculating their participation factors. The coupled modes of the guitar box are discussed taking into account both the finite-element and modal analysis results.

  11. A dual-mode bandpass filter with multiple controllable transmission-zeros using T-shaped stub-loaded resonators.

    PubMed

    Yao, Zh; Wang, C; Kim, N Y

    2014-01-01

    A dual-mode broadband bandpass filter (BPF) with multiple controllable transmission-zeros using T-shaped stub-loaded resonators (TSSLRs) is presented. Due to the symmetrical plane, the odd-even-mode theory can be adopted to characterize the BPF. The proposed filter consists of a dual-mode TSSLR and two modified feed-lines, which introduce two capacitive and inductive source-load (S-L) couplings. Five controllable transmission zeros (TZs) can be achieved for the high selectivity and the wide stopband because of the tunable amount of coupling capacitance and inductance. The center frequency of the proposed BPF is 5.8 GHz, with a 3 dB fraction bandwidth of 8.9%. The measured insertion and return losses are 1.75 and 28.18 dB, respectively. A compact size and second harmonic frequency suppression can be obtained by the proposed BPF with S-L couplings.

  12. A high-overtone bulk acoustic wave resonator-oscillator-based 4.596 GHz frequency source: Application to a coherent population trapping Cs vapor cell atomic clock

    SciTech Connect

    Daugey, Thomas; Friedt, Jean-Michel; Martin, Gilles; Boudot, Rodolphe

    2015-11-15

    This article reports on the design and characterization of a high-overtone bulk acoustic wave resonator (HBAR)-oscillator-based 4.596 GHz frequency source. A 2.298 GHz signal, generated by an oscillator constructed around a thermally controlled two-port aluminum nitride-sapphire HBAR resonator with a Q-factor of 24 000 at 68 °C, is frequency multiplied by 2–4.596 GHz, half of the Cs atom clock frequency. The temperature coefficient of frequency of the HBAR is measured to be −23 ppm/ °C at 2.298 GHz. The measured phase noise of the 4.596 GHz source is −105 dB rad{sup 2}/Hz at 1 kHz offset and −150 dB rad{sup 2}/Hz at 100 kHz offset. The 4.596 GHz output signal is used as a local oscillator in a laboratory-prototype Cs microcell-based coherent population trapping atomic clock. The signal is stabilized onto the atomic transition frequency by tuning finely a voltage-controlled phase shifter implemented in the 2.298 GHz HBAR-oscillator loop, preventing the need for a high-power-consuming direct digital synthesis. The short-term fractional frequency stability of the free-running oscillator is 1.8 × 10{sup −9} at one second integration time. In locked regime, the latter is improved in a preliminary proof-of-concept experiment at the level of 6.6 × 10{sup −11} τ{sup −1/2} up to a few seconds and found to be limited by the signal-to-noise ratio of the detected CPT resonance.

  13. A high-overtone bulk acoustic wave resonator-oscillator-based 4.596 GHz frequency source: Application to a coherent population trapping Cs vapor cell atomic clock

    NASA Astrophysics Data System (ADS)

    Daugey, Thomas; Friedt, Jean-Michel; Martin, Gilles; Boudot, Rodolphe

    2015-11-01

    This article reports on the design and characterization of a high-overtone bulk acoustic wave resonator (HBAR)-oscillator-based 4.596 GHz frequency source. A 2.298 GHz signal, generated by an oscillator constructed around a thermally controlled two-port aluminum nitride-sapphire HBAR resonator with a Q-factor of 24 000 at 68 °C, is frequency multiplied by 2-4.596 GHz, half of the Cs atom clock frequency. The temperature coefficient of frequency of the HBAR is measured to be -23 ppm/ °C at 2.298 GHz. The measured phase noise of the 4.596 GHz source is -105 dB rad2/Hz at 1 kHz offset and -150 dB rad2/Hz at 100 kHz offset. The 4.596 GHz output signal is used as a local oscillator in a laboratory-prototype Cs microcell-based coherent population trapping atomic clock. The signal is stabilized onto the atomic transition frequency by tuning finely a voltage-controlled phase shifter implemented in the 2.298 GHz HBAR-oscillator loop, preventing the need for a high-power-consuming direct digital synthesis. The short-term fractional frequency stability of the free-running oscillator is 1.8 × 10-9 at one second integration time. In locked regime, the latter is improved in a preliminary proof-of-concept experiment at the level of 6.6 × 10-11 τ-1/2 up to a few seconds and found to be limited by the signal-to-noise ratio of the detected CPT resonance.

  14. Optical whispering-gallery mode resonators for applications in optical communication and frequency control

    NASA Astrophysics Data System (ADS)

    Grutter, Karen Esther

    High quality factor (Q) optical whispering gallery mode resonators are a key component in many on-chip optical systems, such as delay lines, modulators, and add-drop filters. They are also a convenient, compact structure for studying optomechanical interactions on-chip. In all these applications, optical Q is an important factor for high performance. For optomechanical reference oscillators in particular, high mechanical Q is also necessary. Previously, optical microresonators have been made in a wide variety of materials, but it has proven challenging to demonstrate high optical Q and high mechanical Q in a single, integrated device. This work demonstrates a new technique for achieving high optical Q on chip, a fully-integrated tunable filter with ultra-narrow minimum bandwidth, and the effect of material choice and device design on optical Q, mechanical Q and phase noise in microring optomechanical oscillators. To achieve a high optical Q, phosphosilicate glass (PSG) is studied as a resonator material. The low melting point of PSG enables wafer-scale reflow, which reduces sidewall roughness without significantly changing lithographically-defined dimensions. With this process, optical Qs up to 1.5 x 10. 7 are achieved, overten times higher than typical silicon optical resonators. These high-Q PSG resonators are then integrated with MEMS-actuated waveguides in a tunable-bandwidth filter. Due to the high Q of the PSG resonator, this device has a best-to-date minimum bandwidth of 0.8 GHz, with a tuning range of 0.8 to 8.5GHz. Finally, microring optomechanical oscillators (OMOs) in PSG, stoichiometric silicon nitride, and silicon are fabricated, and their performance is compared after characterization via a tapered optical fiber in vacuum. The silicon nitride device has the best performance, with a mechanical Q of more than 1 x 10. 4and record-breaking OMO phase noise of -102 dBc/Hz at a 1 kHz offset from a 72 MHz carrier.

  15. Segmented surface coil resonator for in vivo EPR applications at 1.1 GHz

    NASA Astrophysics Data System (ADS)

    Petryakov, Sergey; Samouilov, Alexandre; Chzhan-Roytenberg, Michael; Kesselring, Eric; Sun, Ziqi; Zweier, Jay L.

    2009-05-01

    A four-loop segmented surface coil resonator (SSCR) with electronic frequency and coupling adjustments was constructed with 18 mm aperture and loading capability suitable for in vivo Electron Paramagnetic Resonance (EPR) spectroscopy and imaging applications at L-band. Increased sample volume and loading capability were achieved by employing a multi-loop three-dimensional surface coil structure. Symmetrical design of the resonator with coupling to each loop resulted in high homogeneity of RF magnetic field. Parallel loops were coupled to the feeder cable via balancing circuitry containing varactor diodes for electronic coupling and tuning over a wide range of loading conditions. Manually adjusted high Q trimmer capacitors were used for initial tuning with subsequent tuning electronically controlled using varactor diodes. This design provides transparency and homogeneity of magnetic field modulation in the sample volume, while matching components are shielded to minimize interference with modulation and ambient RF fields. It can accommodate lossy samples up to 90% of its aperture with high homogeneity of RF and modulation magnetic fields and can function as a surface loop or a slice volume resonator. Along with an outer coaxial NMR surface coil, the SSCR enabled EPR/NMR co-imaging of paramagnetic probes in living rats to a depth of 20 mm.

  16. Generation of 10 GHz transform-limited pulse train from dual-pump mode-locking erbium-doped fiber laser

    NASA Astrophysics Data System (ADS)

    He, Li; Yang, Bojun; Zhang, Xiaoguang; Yu, Li

    2006-09-01

    A dual-pump 10 GHz mode-locking erbium-doped fiber laser was demonstrated. With 10-GHz signal modulation of the modulator, less than 12 ps mode-locked pulse at 10 GHz repetition rate with 1.097 mW average output power was obtained. The corresponding spectrum width is 0.277 nm, which is centered at 1561 nm. The corresponding product of time and bandwidth is Δv*Δt which equals 0.433. Gaussian pulse shape is assumed, the output pulse is almost transform limited. Compared with single-pump fiber ring laser, the dual-pump fiber ring laser is helpful for suppression of supermode noise, which make this kind of fiber ring laser more stable.

  17. DWDM channel spacing tunable optical TDM carrier from a mode-locked weak-resonant-cavity Fabry-Perot laser diode based fiber ring.

    PubMed

    Peng, Guo-Hsuan; Chi, Yu-Chieh; Lin, Gong-Ru

    2008-08-18

    A novel optical TDM pulsed carrier with tunable mode spacing matching the ITU-T defined DWDM channels is demonstrated, which is generated from an optically injection-mode-locked weak-resonant-cavity Fabry-Perot laser diode (FPLD) with 10%-end-facet reflectivity. The FPLD exhibits relatively weak cavity modes and a gain spectral linewidth covering >33.5 nm. The least common multiple of the mode spacing determined by both the weak-resonant-cavity FPLD and the fiber-ring cavity can be tunable by adjusting length of the fiber ring cavity or the FPLD temperature to approach the desired 200GHz DWDM channel spacing of 1.6 nm. At a specific fiber-ring cavity length, such a least-common- multiple selection rule results in 12 lasing modes between 1532 and 1545 nm naturally and a mode-locking pulsewidth of 19 ps broadened by group velocity dispersion among different modes. With an additional intracavity bandpass filter, the operating wavelength can further extend from 1520 to 1553.5 nm. After channel filtering, each selected longitudinal mode gives rise to a shortened pulsewidth of 12 ps due to the reduced group velocity dispersion. By linear dispersion compensating with a 55-m long dispersion compensation fiber (DCF), the pulsewidth can be further compressed to 8 ps with its corresponding peak-to-peak chirp reducing from 9.7 to 4.3 GHz.

  18. A SETI Search of Nearby Solar-Type Stars at the 203-GHz Positronium Hyperfine Resonance

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.; DeBoer, David R.

    1994-01-01

    The development of advanced millimeter-wave technology has made it possible to construct low-noise receivers and high-power transmitters comparable to those available at much lower frequencies. This technology, plus certain physical characteristics of the millimeter-wave spectrum, suggests possible advantages for use of this wavelength range for interstellar communications. As a result, a Search for ExtraTerrestrial Intelligence(SETI) type search has been conducted for narrow-bandwidth signals at frequencies near the positronium hyperfine spectral line (203.385 GHz), a potential natural reference frequency. A total of 40 solar-type stars within 23 parsecs were observed, in addition to three locations near the galactic center. No detections were made at the detection threshold of 2.3 x 10(exp -19) W/sq m in each of two orthogonal linear polarizations Future observations will be made with a higher resolution Fast Fourier Transform Spectrum Analyzer (FFTSA), which should improve sensitivity by an order of magnitude and reduce required observing time.

  19. A SETI Search of Nearby Solar-Type Stars at the 203-GHz Positronium Hyperfine Resonance

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.; DeBoer, David R.

    1994-01-01

    The development of advanced millimeter-wave technology has made it possible to construct low-noise receivers and high-power transmitters comparable to those available at much lower frequencies. This technology, plus certain physical characteristics of the millimeter-wave spectrum, suggests possible advantages for use of this wavelength range for interstellar communications. As a result, a Search for ExtraTerrestrial Intelligence(SETI) type search has been conducted for narrow-bandwidth signals at frequencies near the positronium hyperfine spectral line (203.385 GHz), a potential natural reference frequency. A total of 40 solar-type stars within 23 parsecs were observed, in addition to three locations near the galactic center. No detections were made at the detection threshold of 2.3 x 10(exp -19) W/sq m in each of two orthogonal linear polarizations Future observations will be made with a higher resolution Fast Fourier Transform Spectrum Analyzer (FFTSA), which should improve sensitivity by an order of magnitude and reduce required observing time.

  20. Guided-mode resonance nanophotonics in materially sparse architectures

    NASA Astrophysics Data System (ADS)

    Magnusson, Robert; Niraula, Manoj; Yoon, Jae W.; Ko, Yeong H.; Lee, Kyu J.

    2016-03-01

    The guided-mode resonance (GMR) concept refers to lateral quasi-guided waveguide modes induced in periodic layers. Whereas these effects have been known for a long time, new attributes and innovations continue to appear. Here, we review some recent progress in this field with emphasis on sparse, or minimal, device embodiments. We discuss properties of wideband resonant reflectors designed with gratings in which the grating ridges are matched to an identical material to eliminate local reflections and phase changes. This critical interface therefore possesses zero refractive-index contrast; hence we call them "zero-contrast gratings." Applying this architecture, we present single-layer, wideband reflectors that are robust under experimentally realistic parametric variations. We introduce a new class of reflectors and polarizers fashioned with dielectric nanowire grids that are mostly empty space. Computed results predict high reflection and attendant polarization extinction for these sparse lattices. Experimental verification with Si nanowire grids yields ~200-nm-wide band of high reflection for one polarization state and free transmission of the orthogonal state. Finally, we present bandpass filters using all-dielectric resonant gratings. We design, fabricate, and test nanostructured single layer filters exhibiting high efficiency and sub-nanometer-wide passbands surrounded by 100-nm-wide stopbands.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  2. Selective mode coupling in microring resonators for single mode semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Arbabi, Amir

    Single mode semiconductor laser diodes have many applications in optical communications, metrology and sensing. Edge-emitting single mode lasers commonly use distributed feedback structures, or narrowband reflectors such as distributed Bragg reflectors (DBRs) and sampled grating distributed Bragg reflectors (SGDBRs). Compact, narrowband reflectors with high reflectivities are of interest to replace the commonly used DBRs and SGDBRs. This thesis presents our work on the simulation, design, fabrication, and characterization of devices operating based on the coupling of degenerate modes of a microring resonator, and investigation of the possibility of using them for improving the performance of laser diodes. In particular, we demonstrate a new type of compact, narrowband, on-chip reflector realized by selectively coupling degenerate modes of a microring resonator. For the simulation and design of reflective microring resonators, a fast and accurate analysis method is required. Conventional numerical methods for solving Maxwell's equations such as the finite difference time domain and the finite element method (FEM) provide accurate results but are computationally intense and are not suitable for the design of large 3D structures. We formulated a set of coupled mode equations that, combined with 2D FEM simulations, can provide a fast and accurate tool for the modeling and design of reflective microrings. We developed fabrication processing recipes and fabricated passive reflective microrings on silicon substrates with a silicon nitride core and silicon dioxide cladding. Narrowband single wavelength reflectors were realized which are 70 times smaller than a conventional DBR with the same bandwidth. Compared to the conventional DBR, they have faster roll-off, and no side modes. The smaller footprint saves real estate, reduces tuning power and makes these devices attractive as in-line mirrors for low threshold narrow linewidth laser diodes. Self-heating caused by material

  3. 10 GHz, 1.1 ps optical pulse generation from a regeneratively mode-locked Yb fiber laser in the 1.1 μm band.

    PubMed

    Koizumi, Kengo; Yoshida, Masato; Hirooka, Toshihiko; Nakazawa, Masataka

    2011-12-05

    We report a 10 GHz harmonically and regeneratively mode-locked Yb fiber laser with a phase-locked loop (PLL) technique at 1.1 μm. Stable mode locking was achieved by optimizing the average dispersion of the fiber cavity to an anomalous dispersion to operate as a soliton laser. As a result, a 1.1 ps optical pulse with a timing jitter of 140 fs was successfully generated.

  4. Whispering-gallery mode micro-kylix resonators.

    PubMed

    Ghulinyan, Mher; Pitanti, Alessandro; Pucker, Georg; Pavesi, Lorenzo

    2009-05-25

    Owing to their ability to confine electromagnetic energy in ultrasmall dielectric volumes, micro-disk, ring and toroid resonators hold interest for both specific applications and fundamental investigations. Generally, contributions from various loss channels within these devices lead to limited spectral windows (Q-bands) where highest mode Q-factors manifest. Here we describe a strategy for tuning Q-bands using a new class of micro-resonators, named micro-kylix resonators, in which engineered stress within an initially flat disk results in either concave or convex devices. To shift the Q-band by 60 nm towards short wavelengths in flat micro-disks a 50% diameter reduction is required, which causes severe radiative losses suppressing Q's. With a micro-kylix, we achieve similar tuning and even higher Q's by two orders of magnitude smaller diameter modification (0.4%). The phenomenon relies on geometry-induced smart interplay between modified dispersions of material absorption and radiative loss-related Q-factors. Micro-kylix devices can provide new functionalities and novel technological solutions for photonics and micro-resonator physics.

  5. Development of a new superconducting electron cyclotron resonance ion source for operations up to 18 GHz at LBNL

    SciTech Connect

    Xie, D. Z. Benitez, J. Y.; Hodgkinson, A.; Lyneis, C. M.; Phair, L. W.; Strohmeier, M. M.; Thuillier, T. P.; Todd, D. S.; Caspi, S.; Prestemon, S. O.

    2014-02-15

    A new superconducting Electron Cyclotron Resonance Ion Source (ECRIS) is under development at LBNL to harness the winding techniques of a closed-loop sextupole coil for the next generation ECRIS and to enhance the capability of the 88-in. cyclotron facility. The proposed ECRIS will use a superconducting closed-loop sextupole coil to produce the radial field and a substantial portion of the axial field. The field strengths of the injection, central and extraction regions are adjusted by a three solenoids outside the closed-loop sextupole coil. In addition to maintaining the typical ECRIS magnetic field configuration, this new source will also be able to produce a dustpan-like minimum-B field to explore possible ECRIS performance enhancement. The dustpan-like minimum-B field configuration has about the same strengths for the maximum axial field at the injection region and the maximum radial pole fields at the plasma chamber walls but it can be substantially lower at the extraction region. The dustpan-like minimum-B will have a field maximum B{sub max} ≥ 2.6 T for operations up to 18 GHz with a ratio of B{sub max}/B{sub res} ≥ 4 and higher ratios for lower frequencies. The field maxima of this new source can reach over 3 T both at the injection and the plasma chamber walls which could also support operation at 28 GHz. The source will be built of cryogen-free with the magnets directly cooled by cryo-coolers to simplify the cryostat structure. The source design features will be presented and discussed.

  6. Development of a new superconducting Electron Cyclotron Resonance Ion Source for operations up to 18 GHz at LBNL.

    PubMed

    Xie, D Z; Benitez, J Y; Caspi, S; Hodgkinson, A; Lyneis, C M; Phair, L W; Prestemon, S O; Strohmeier, M M; Thuillier, T P; Todd, D S

    2014-02-01

    A new superconducting Electron Cyclotron Resonance Ion Source (ECRIS) is under development at LBNL to harness the winding techniques of a closed-loop sextupole coil for the next generation ECRIS and to enhance the capability of the 88-in. cyclotron facility. The proposed ECRIS will use a superconducting closed-loop sextupole coil to produce the radial field and a substantial portion of the axial field. The field strengths of the injection, central and extraction regions are adjusted by a three solenoids outside the closed-loop sextupole coil. In addition to maintaining the typical ECRIS magnetic field configuration, this new source will also be able to produce a dustpan-like minimum-B field to explore possible ECRIS performance enhancement. The dustpan-like minimum-B field configuration has about the same strengths for the maximum axial field at the injection region and the maximum radial pole fields at the plasma chamber walls but it can be substantially lower at the extraction region. The dustpan-like minimum-B will have a field maximum Bmax ≥ 2.6 T for operations up to 18 GHz with a ratio of Bmax/Bres ≥ 4 and higher ratios for lower frequencies. The field maxima of this new source can reach over 3 T both at the injection and the plasma chamber walls which could also support operation at 28 GHz. The source will be built of cryogen-free with the magnets directly cooled by cryo-coolers to simplify the cryostat structure. The source design features will be presented and discussed.

  7. Protein-modified shear mode film bulk acoustic resonator for bio-sensing applications

    NASA Astrophysics Data System (ADS)

    Wang, Jingjing; Liu, Weihui; Xu, Yan; Chen, Da; Li, Dehua; Zhang, Luyin

    2014-09-01

    In this paper, we present a shear mode film bulk acoustic biosensor based on micro-electromechanical technology. The film bulk acoustic biosensor is a diaphragmatic structure consisting of a lateral field excited ZnO piezoelectric film piezoelectric stack built on an Si3N4 membrane. The device works at near 1.6 GHz with Q factors of 579 in water and 428 in glycerol. A frequency shift of 5.4 MHz and a small decline in the amplitude are found for the measurements in glycerol compared with those in water because of the viscous damping derived from the adjacent glycerol. For bio-sensing demonstration, the resonator was modified with biotin molecule to detect protein-ligand interactions in real-time and in situ. The resonant frequency of the biotin-modified device drops rapidly and gradually reaches equilibrium when exposed to the streptavidin solution due to the biotin-streptavidin interaction. The proposed film bulk acoustic biosensor shows promising applications for disease diagnostics, prognosis, and drug discovery.

  8. Resonance modes filtering in structured x-ray waveguides

    NASA Astrophysics Data System (ADS)

    Bukreeva, Inna; Cedola, Alessia; Sorrentino, Andrea; Pelliccia, Daniele; Asadchikov, Viktor; Lagomarsino, Stefano

    2011-07-01

    We discuss the self-imaging effect that occurs in a multimode planar x-ray waveguide (WG) with a nanometer vacuum gap, where an additional longitudinal periodicity has been imposed by a periodical structure (a micron scale step-like grating) on the reflecting sidewalls. Taking into account the general Montgomery conditions and the particular case of Talbot effect, we show that this additional longitudinal periodicity, if suitably designed, can filter out the asymmetric and the high order resonance modes, providing a coherent beam at the exit, even if the WG is illuminated by an incoherent source.

  9. Design rules for lossy mode resonance based sensors.

    PubMed

    Del Villar, Ignacio; Hernaez, Miguel; Zamarreño, Carlos R; Sánchez, Pedro; Fernández-Valdivielso, Carlos; Arregui, Francisco J; Matias, Ignacio R

    2012-07-01

    Lossy mode resonances can be obtained in the transmission spectrum of cladding removed multimode optical fiber coated with a thin-film. The sensitivity of these devices to changes in the properties of the coating or the surrounding medium can be optimized by means of the adequate parameterization of the coating refractive index, the coating thickness, and the surrounding medium refractive index. Some basic rules of design, which enable the selection of the best parameters for each specific sensing application, are indicated in this work.

  10. Method of fabricating a whispering gallery mode resonator

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy A. (Inventor); Matkso, Andrey B. (Inventor); Iltchenko, Vladimir S. (Inventor); Maleki, Lute (Inventor)

    2011-01-01

    A method of fabricating a whispering gallery mode resonator (WGMR) is provided. The WGMR can be fabricated from a particular material, annealed, and then polished. The WGMR can be repeatedly annealed and then polished. The repeated polishing of the WGMR can be carried out using an abrasive slurry. The abrasive slurry can have a predetermined, constant grain size. Each subsequent polishing of the WGMR can use an abrasive slurry having a grain size that is smaller than the grain size of the abrasive slurry of the previous polishing iteration.

  11. Cavity-resonator-integrated guided-mode resonance filter for aperture miniaturization.

    PubMed

    Kintaka, Kenji; Majima, Tatsuya; Inoue, Junichi; Hatanaka, Koji; Nishii, Junji; Ura, Shogo

    2012-01-16

    A guided-mode resonance filter integrated in a waveguide cavity resonator constructed by two distributed Bragg reflectors is designed and fabricated for miniaturization of aperture size. Reflection efficiency of >90% and wavelength selectivity of 0.4 nm are predicted in the designed SiO(2)-based filter with 50-μm aperture by a numerical calculation using the finite-difference time-domain method. A maximum reflectance of 67% with 0.5-nm bandwidth is experimentally demonstrated by the fabricated device at around 850-nm wavelength.

  12. Dynamic Fano-like resonances in erbium-doped whispering-gallery-mode microresonators

    SciTech Connect

    Lei, Fuchuan; Peng, Bo; Özdemir, Şahin Kaya Yang, Lan; Long, Gui Lu

    2014-09-08

    We report Fano-like asymmetric resonances modulated by optical gain in a whispering-gallery-mode resonator fabricated from erbium-doped silica. A time-dependent gain profile leads to dynamically varying sharp asymmetric resonances with features similar to Fano resonances. Depending on the scan speed of the frequency of the probe laser and the pump-probe power ratio, transmission spectra of the active microcavity exhibit a resonance dip, a resonance peak, or a Fano-like resonance.

  13. Bio-molecular sensors based on guided mode resonance filters

    NASA Astrophysics Data System (ADS)

    Saleem, M. R.; Ali, R.; Honkanen, S.; Turunen, J.

    2016-08-01

    In this work a low surface roughness and homogenous, high refractive index, and amorphous TiO2 layer on corrugated structures of diffractive optical element is coated by Atomic Layer Deposition (ALD) for biosensors. The design of Guided Mode Resonance Filters (GMRFs) is based on refractive indices and thicknesses of the waveguide biomolecular layers. The designed spectral shifts are calculated by Fourier Modal Method (FMM) and depend on the magnitude of the variations in refractive index of the biomolecular layer on waveguide structures. Furthermore, the sensitivity of the biomolecular sensors depends on the thickness of biomolecular layer and periodicity of the structures. The waveguide structures designed for larger periods show an enhancement in the sensitivity (nm/RIU) of the biomolecular sensor at longer wavelengths. The periodicities of nanophotonic structures are varied from 300 to 500 nm in design calculations with predominance of increase in effective index of the structure to support leaky waveguide modes.

  14. Upgrade Of The TH1506B 118 GHz Gyrotron Using Modeing Tools

    SciTech Connect

    Darbos, C.; Bouquey, F.; Lambert, R.; Magne, R.; Traisnel, E.; Prinz, H. O.; Thumm, M.; Hogge, J. P.; Lievin, C.

    2007-09-28

    The first TH1506B prototype showing problems of overheating and spurious oscillations, a new modified gyrotron was built. During the tests, the extwo peaks, which was never predicted by simulations. Various low evel tests were performed on the mode converter with different shapes for the launcher but without real improvement. Besides measurements, the use of a new software Surf3D[l] showed that the problem mainly comes from the 3rd mirror whose curvature is too high and not well taken nto account by the calculation. This analysis software is based on ntegral equations and the complete 3D modelling alowed to determine a new profile for the 3rd mirror. An aluminium model of a new mirror was manufactured and thorough low level tests made at FZK showed that there was no double peak.The next step would consist in building a gyrotron based on this new design, to confirm the simulation and to valdate it for long pulses.

  15. Mechanism of Edge Localized Mode Mitigation by Resonant Magnetic Perturbations

    NASA Astrophysics Data System (ADS)

    Bécoulet, M.; Orain, F.; Huijsmans, G. T. A.; Pamela, S.; Cahyna, P.; Hoelzl, M.; Garbet, X.; Franck, E.; Sonnendrücker, E.; Dif-Pradalier, G.; Passeron, C.; Latu, G.; Morales, J.; Nardon, E.; Fil, A.; Nkonga, B.; Ratnani, A.; Grandgirard, V.

    2014-09-01

    A possible mechanism of edge localized modes (ELMs) mitigation by resonant magnetic perturbations (RMPs) is proposed based on the results of nonlinear resistive magnetohydrodynamic modeling using the jorek code, realistic JET-like plasma parameters and an RMP spectrum of JET error-field correction coils (EFCC) with a main toroidal number n =2 were used in the simulations. Without RMPs, a large ELM relaxation is obtained mainly due to the most unstable medium-n ballooning mode. The externally imposed RMP drives nonlinearly the modes coupled to n =2 RMP which produce small multimode relaxations, mitigated ELMs. The modes driven by RMPs exhibit a tearinglike structure and produce additional islands. Mitigated ELMs deposit energy into the divertor mainly in the structures ("footprints") created by n =2 RMPs, however, slightly modulated by other nonlinearly driven even harmonics. The divertor power flux during a ELM phase mitigated by RMPs is reduced almost by a factor of 10. The mechanism of ELM mitigation by RMPs proposed here reproduces generic features of high collisionality RMP experiments, where large ELMs are replaced by small, much more frequent ELMs or magnetic turbulence. Total ELM suppression was also demonstrated in modeling at higher RMP amplitude.

  16. Mechanism of edge localized mode mitigation by resonant magnetic perturbations.

    PubMed

    Bécoulet, M; Orain, F; Huijsmans, G T A; Pamela, S; Cahyna, P; Hoelzl, M; Garbet, X; Franck, E; Sonnendrücker, E; Dif-Pradalier, G; Passeron, C; Latu, G; Morales, J; Nardon, E; Fil, A; Nkonga, B; Ratnani, A; Grandgirard, V

    2014-09-12

    A possible mechanism of edge localized modes (ELMs) mitigation by resonant magnetic perturbations (RMPs) is proposed based on the results of nonlinear resistive magnetohydrodynamic modeling using the jorek code, realistic JET-like plasma parameters and an RMP spectrum of JET error-field correction coils (EFCC) with a main toroidal number n=2 were used in the simulations. Without RMPs, a large ELM relaxation is obtained mainly due to the most unstable medium-n ballooning mode. The externally imposed RMP drives nonlinearly the modes coupled to n=2 RMP which produce small multimode relaxations, mitigated ELMs. The modes driven by RMPs exhibit a tearinglike structure and produce additional islands. Mitigated ELMs deposit energy into the divertor mainly in the structures ("footprints") created by n=2 RMPs, however, slightly modulated by other nonlinearly driven even harmonics. The divertor power flux during a ELM phase mitigated by RMPs is reduced almost by a factor of 10. The mechanism of ELM mitigation by RMPs proposed here reproduces generic features of high collisionality RMP experiments, where large ELMs are replaced by small, much more frequent ELMs or magnetic turbulence. Total ELM suppression was also demonstrated in modeling at higher RMP amplitude.

  17. Attenuation process of the longitudinal phonon mode in a TeO2 crystal in the 20-GHz range

    NASA Astrophysics Data System (ADS)

    Ohno, S.; Sonehara, T.; Tatsu, E.; Koreeda, A.; Saikan, S.

    2017-06-01

    We experimentally investigated the hypersonic attenuation process of a longitudinal mode (L-mode) sound wave in TeO2 from room temperature to a lower temperature using Brillouin scattering and impulsive stimulated thermal scattering (ISTS) measurements. For precise measurement of the Brillouin linewidth at low temperatures, whereby the mean free path of the phonon becomes longer than the sample length, it is indispensable that the phonon should propagate along the phonon-resonance direction. To figure out the suitable direction, we defined two indices characterizing a degree of phonon divergence and a purity of propagation direction. The best direction that we found from these indices is [110] direction in TeO2, and it was used to discuss the temperature and frequency dependences of Brillouin spectra. We extracted the temperature dependence of the attenuation rate of T4 from the modulated Brillouin spectra due to the phonon resonance below Debye temperature. The frequency dependence ω1 of the hypersonic attenuation was also estimated from the polarization dependence of the Brillouin linewidth. Theoretically, it predicted that the L-mode phonon attenuation at low temperatures in TeO2 is a result of Herring's process, which shows the attenuation behavior of ω2T3 . The ω1T4 dependence is not allowed in Herring's process but is allowed by the L +L →L process, which has been considered to be forbidden so far. We evaluated the thermal phonon lifetime using ISTS and established that it was finite even at 20 K, thereby allowing the L +L →L process. Therefore, we conclude that the L +L →L process dominates the attenuation of an L-mode phonon in TeO2 in the low-temperature region.

  18. Ultrasonic resonant modes of piezoelectric balloons under internal pressure.

    PubMed

    Denham, Lori Vidal; Rice, David A

    2012-09-01

    Properties of a piezoelectric polymeric angioplasty balloon that may decrease the problems of acute closure and restenosis are evaluated in this study. Polyvinylidene difluoride (PVDF), a piezoelectric and pyroelectric polymer, has sufficient strength to serve as a standard angioplasty balloon as well as functioning as an ultrasonic transmitter and/or receiver. These properties enable potential therapeutic applications using ultrasound such as plaque ablation and sonotherapy as well as vulnerable plaque diagnosis using thermography. This study investigates the resonant structure of the PVDF balloon catheter in the frequency range 5-100 kHz. Vibrations of the piezoelectric balloon are modeled using cylindrical shell theory and compared with the observed modal frequencies of PVDF cylinders with and without internal pressure. Modal frequencies are determined by measuring the near-field pressure response of the PVDF cylinders using a high frequency microphone. A rich nodal structure is observed between 5 and 100 kHz with peak relative amplitudes measured between 42 and 45 kHz. Higher order modes for cylinders with 9 μm and 28 μm wall thickness increase in frequency as the internal pressure is increased. Experimental measurements confirm theoretical models that predict both pressure-dependent and pressure-independent resonant frequencies. Frequencies of pressure-dependent modes are calculated within 2.2% of measured values at high pressure.

  19. Reservoir Engineering of Two-mode Correlations in Mechanical Resonators

    NASA Astrophysics Data System (ADS)

    Chang, Laura; Patil, Yogesh Sharad; Chakram, Srivatsan; Vengalattore, Mukund

    2015-05-01

    Nonlinear mechanical interactions in the quantum limit enable the manipulation and control of phonons in a manner akin to quantum optics in nonlinear media. We demonstrate, for the first time, strong quantum-compatible multimode nonlinearities in a low-loss mechanical resonator that is amenable to ground state optomechanical cooling, room temperature quantum control and quantum limited detection. These nonlinearities arise from substrate-mediated interactions between distinct modes of the resonator. We develop a model for this nonlinearity that accurately describes the experimental observations over three orders of magnitude in dynamic range, demonstrating the robustness and fidelity of the engineered nonlinear interactions. We use this nonlinearity to realize a mechanical nondegenerate parametric amplifier, and use it to demonstrate two-mode thermomechanical noise squeezing. Our work opens new opportunities for nonlinear approaches to quantum metrology, transduction between optical and phononic fields, and the quantum manipulation of phononic degrees of freedom. This work is supported by the DARPA QuASAR program through a grant from the ARO and an NSF INSPIRE award.

  20. Cavity-resonator-integrated guided-mode resonance band-stop reflector.

    PubMed

    Ura, Shogo; Nakata, Masahiro; Yanagida, Kenichi; Inoue, Junichi; Kintaka, Kenji

    2016-06-27

    A cavity-resonator-integrated guided-mode resonance filter (CRIGF) consists of a grating coupler inside a pair of distributed Bragg reflectors. A combination of a CRIGF with a high-reflection substrate can provide a new type of a band-stop reflector with a small aperture for a vertically incident wave from air. A narrow stopband was theoretically predicted and experimentally demonstrated. It was quantitatively shown that reflection spectra depended on optical-buffer-layer thickness. The reflector of 10-μm aperture was fabricated and characterized. The extinction ratio in reflectance was measured to be lower than -20 dB at a resonance wavelength. The bandwidth at -3 dB was 0.15 nm.

  1. Coupled-mode-theory framework for nonlinear resonators comprising graphene

    NASA Astrophysics Data System (ADS)

    Christopoulos, Thomas; Tsilipakos, Odysseas; Grivas, Nikolaos; Kriezis, Emmanouil E.

    2016-12-01

    A general framework combining perturbation theory and coupled-mode theory is developed for analyzing nonlinear resonant structures comprising dispersive bulk and sheet materials. To allow for conductive sheet materials, a nonlinear current term is introduced in the formulation in addition to the more common nonlinear polarization. The framework is applied to model bistability in a graphene-based traveling-wave resonator system exhibiting third-order nonlinearity. We show that the complex conductivity of graphene disturbs the equality of electric and magnetic energies on resonance (a condition typically taken for granted), due to the reactive power associated with the imaginary part of graphene's surface conductivity. Furthermore, we demonstrate that the dispersive nature of conductive materials must always be taken into account, since it significantly impacts the nonlinear response. This is explained in terms of the energy stored in the surface current, which is zeroed-out when linear dispersion is neglected. The results obtained with the proposed framework are compared with full-wave nonlinear finite-element simulations with excellent agreement. Very low characteristic power for bistability is obtained, indicating the potential of graphene for nonlinear applications.

  2. Coupled-mode-theory framework for nonlinear resonators comprising graphene.

    PubMed

    Christopoulos, Thomas; Tsilipakos, Odysseas; Grivas, Nikolaos; Kriezis, Emmanouil E

    2016-12-01

    A general framework combining perturbation theory and coupled-mode theory is developed for analyzing nonlinear resonant structures comprising dispersive bulk and sheet materials. To allow for conductive sheet materials, a nonlinear current term is introduced in the formulation in addition to the more common nonlinear polarization. The framework is applied to model bistability in a graphene-based traveling-wave resonator system exhibiting third-order nonlinearity. We show that the complex conductivity of graphene disturbs the equality of electric and magnetic energies on resonance (a condition typically taken for granted), due to the reactive power associated with the imaginary part of graphene's surface conductivity. Furthermore, we demonstrate that the dispersive nature of conductive materials must always be taken into account, since it significantly impacts the nonlinear response. This is explained in terms of the energy stored in the surface current, which is zeroed-out when linear dispersion is neglected. The results obtained with the proposed framework are compared with full-wave nonlinear finite-element simulations with excellent agreement. Very low characteristic power for bistability is obtained, indicating the potential of graphene for nonlinear applications.

  3. Raman-assisted Rabi resonances in two-mode cavity QED

    SciTech Connect

    Gruenwald, P.; Singh, S. K.; Vogel, W.

    2011-06-15

    The dynamics of a vibronic system in a lossy two-mode cavity is studied, with the first mode being resonant to the electronic transition and the second one being nearly resonant due to Raman transitions. We derive analytical solutions for the dynamics of this system. For a properly chosen detuning of the second mode from the exact Raman resonance, we obtain conditions that are closely related to the phenomenon of Rabi resonance as it is well known in laser physics. Such resonances can be observed in the spontaneous emission spectra, where the spectrum of the second mode in the case of weak Raman coupling is enhanced substantially.

  4. Guided mode resonance enabled ultra-compact Germanium photodetector for 1.55 μm detection.

    PubMed

    Zhu, Alexander Yutong; Zhu, Shiyang; Lo, Guo-Qiang

    2014-02-10

    We propose a novel technique of enhancing the photodetection capabilities of ultrathin Ge films for normally incident light at 1.55 μm through the guided mode resonance (GMR) phenomenon. Specifically, by suitably patterning the surface of a Ge thin film, it is possible to excite guided modes which are subsequently coupled to free space radiative modes, resulting in spectral resonances that possess locally enhanced near fields with a large spatial extent. Absorption is found to be enhanced by over an order of magnitude over a pristine Ge film of equal thickness. Furthermore, attenuation of incident light for such a structure occurs over very few grating periods, resulting in significantly enhanced theoretical 3 dB bandwidth-efficiency products of ~58 GHz. The nature of the enhancement mechanism also produces spectrally narrow resonances (FWHM ~30 nm) that are polarization sensitive and exhibit excellent angular tolerance. Finally, the proposed device architecture is fully compatible with existing Si infrastructure and current CMOS fabrication processes.

  5. Radiofrequency and 2.45 GHz electron cyclotron resonance H- volume production ion sources

    NASA Astrophysics Data System (ADS)

    Tarvainen, O.; Peng, S. X.

    2016-10-01

    The volume production of negative hydrogen ions ({{{H}}}-) in plasma ion sources is based on dissociative electron attachment (DEA) to rovibrationally excited hydrogen molecules (H2), which is a two-step process requiring both, hot electrons for ionization, and vibrational excitation of the H2 and cold electrons for the {{{H}}}- formation through DEA. Traditionally {{{H}}}- ion sources relying on the volume production have been tandem-type arc discharge sources equipped with biased filament cathodes sustaining the plasma by thermionic electron emission and with a magnetic filter separating the main discharge from the {{{H}}}- formation volume. The main motivation to develop ion sources based on radiofrequency (RF) or electron cyclotron resonance (ECR) plasma discharges is to eliminate the apparent limitation of the cathode lifetime. In this paper we summarize the principles of {{{H}}}- volume production dictating the ion source design and highlight the differences between the arc discharge and RF/ECR ion sources from both, physics and technology point-of-view. Furthermore, we introduce the state-of-the-art RF and ECR {{{H}}}- volume production ion sources and review the challenges and future prospects of these yet developing technologies.

  6. High-frequency (95 GHz) electron paramagnetic resonance study of the photoinduced charge transfer in conjugated polymer-fullerene composites

    NASA Astrophysics Data System (ADS)

    Ceuster, J. De; Goovaerts, E.; Bouwen, A.; Hummelen, J. C.; Dyakonov, V.

    2001-11-01

    Light-induced electron paramagnetic resonance (LEPR) measurements are reported in composites of poly(2-methoxy-5-(3-,7-dimethyloctyloxy)-1,4-phenylenevinylene) (MDMO-PPV) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), a soluble derivative of C60. Under illumination of the sample, two paramagnetic species are formed due to photoinduced charge transfer between conjugated polymer and fullerene. One is the positive polaron P+ on the polymer backbone and the other is the radical anion on the methanofullerene. Using high-frequency (95 GHz) LEPR it was possible to separate these two contributions to the spectrum on the basis of their g factors, and moreover to resolve the g anisotropy for both radicals. The positive polaron on the conjugated polymer chain possesses axial symmetry with g values g||=2.0034(1) and g⊥=2.0024(1). EPR on low doped polymer gave extra proof for the assignment to the positive polaron. The negatively charged methanofullerene has a lower, rhombic symmetry with gx=2.0003(1), gy=2.0001(1), and gz=1.9982(1). Different spin-lattice relaxation of both species gives rise to a rapid passage effect for the positive polaron spectrum.

  7. Production of highly charged heavy ions by 18 GHz superconducting electron cyclotron resonance at Research Center for Nuclear Physics.

    PubMed

    Yorita, Tetsuhiko; Hatanaka, Kichiji; Fukuda, Mitsuhiro; Kibayashi, Mitsuru; Morinobu, Shunpei; Okamura, Hiroyuki; Tamii, Atsushi

    2010-02-01

    An 18 GHz superconducting electron cyclotron resonance ion source has been installed as a subject of the azimuthally varying field cyclotron upgrade project (K. Hatanaka et al., in Proceedings of the 17th International Conference on Cyclotrons and Their Applications, Tokyo, Japan, 18-22 October 2004, pp. 115-117), in order to increase beam currents and to extend the variety of ions. The production development of several ions has been performed since 2006 and some of them have already been used for user experiments [T. Yorita et al., Rev. Sci. Instrum. 79, 02A311 (2008)]. Further optimizations for each component such as the material of plasma electrode, material, and shape of bias probe and mirror field have been continued and more intense ion beams have been obtained for O, N, and Ar. For the purpose of obtaining highly charged Xe with several microamperes, the optimization of position and shape of plasma electrode and bias disk has also been done and highly charged Xe(32+) beam has been obtained successfully.

  8. Vibrational modes of ultrathin carbon nanomembrane mechanical resonators

    SciTech Connect

    Zhang, Xianghui E-mail: elke.scheer@uni-konstanz.de; Angelova, Polina; Gölzhäuser, Armin; Waitz, Reimar; Yang, Fan; Lutz, Carolin; Scheer, Elke E-mail: elke.scheer@uni-konstanz.de

    2015-02-09

    We report measurements of vibrational mode shapes of mechanical resonators made from ultrathin carbon nanomembranes (CNMs) with a thickness of approximately 1 nm. CNMs are prepared from electron irradiation induced cross-linking of aromatic self-assembled monolayers and the variation of membrane thickness and/or density can be achieved by varying the precursor molecule. Single- and triple-layer freestanding CNMs were made by transferring them onto Si substrates with square/rectangular orifices. The vibration of the membrane was actuated by applying a sinusoidal voltage to a piezoelectric disk on which the sample was glued. The vibrational mode shapes were visualized with an imaging Mirau interferometer using a stroboscopic light source. Several mode shapes of a square membrane can be readily identified and their dynamic behavior can be well described by linear response theory of a membrane with negligible bending rigidity. By applying Fourier transformations to the time-dependent surface profiles, the dispersion relation of the transverse membrane waves can be obtained and its linear behavior verifies the membrane model. By comparing the dispersion relation to an analytical model, the static stress of the membranes was determined and found to be caused by the fabrication process.

  9. Narrowband Mid-infrared reflectance filters using guided mode resonance

    PubMed Central

    Kodali, Anil K.; Schulmerich, Matthew; Ip, Jason; Yen, Gary; Cunningham, Brian T.; Bhargava, Rohit

    2010-01-01

    There is a need to develop mid-infrared (IR) spectrometers for applications in which the absorbance of only a few vibrational mode (optical) frequencies needs to be recorded; unfortunately, there are limited alternatives for the same. The key requirement is the development of a means to access discretely a small set of spectral positions from the wideband thermal sources commonly used for spectroscopy. We present here the theory, design and practical realization of a new class of filters in the mid-infrared (IR) spectral regions based on using guided mode resonances (GMR) for narrowband optical reflection. A simple, periodic surface-relief configuration is chosen to enable both a spectral response and facile fabrication. A theoretical model based on rigorous coupled wave analysis is developed, incorporating anomalous dispersion of filter materials in the mid-IR spectral region. As a proof-of-principle demonstration, a set of four filters for a spectral region around the C-H stretching mode (2600–3000 cm−1) are fabricated and responses compared to theory. The reflectance spectra were well-predicted by the developed theory and results were found to be sensitive to the angle of incidence and dispersion characteristics of the material. In summary, the work reported here forms the basis for a rational design of filters that can prove useful for IR absorption spectroscopy. PMID:20527738

  10. Tunable Optical Filters Having Electro-optic Whispering-gallery-mode Resonators

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy (Inventor); Ilchenko, Vladimir (Inventor); Matsko, Andrey B. (Inventor); Maleki, Lutfollah (Inventor)

    2006-01-01

    Tunable optical filters using whispering-gallery-mode (WGM) optical resonators are described. The WGM optical resonator in a filter exhibits an electro-optical effect and hence is tunable by applying a control electrical signal.

  11. Mode selection for electrostatic beam resonators based on motional resistance and quality factor.

    PubMed

    Ryou, Jeong Hoon; Gorman, Jason J

    2016-12-07

    An analytical comparison between the fundamental mode and higher modes of vibration for an electrostatic beam resonator is presented. Multiple mode numbers can be matched to a desired resonance frequency through appropriate scaling. Therefore, it is important to determine which mode yields the best performance. A dynamic model of the resonator is derived and then used to determine the motional resistance for each mode. The resulting equation provides the basis for comparing performance between modes using motional resistance and quality factor. As a demonstration of the approach, a quality factor model that has been previously validated experimentally is introduced. Numerical results for silicon resonators indicate that the fundamental mode can provide a lower motional resistance and higher quality factor when the resonators under comparison have the same aspect ratio or the same stiffness.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  13. Localized surface plasmon resonance modes on an asymmetric cylindrical nanorod dimer

    NASA Astrophysics Data System (ADS)

    Wang, Rui-Bing; Zhang, Zhi-Dong; Jiao, Guo-Tai; Xue, Chen-Yang; Yan, Shu-Bin; Wang, Hongyang

    2016-08-01

    The extinction spectra and electric field distribution of an asymmetric cylindrical nanorod dimer (ACND) are calculated by discrete dipole approximation. The ACND is composed of two linear orders of cylindrical silver nanorods with different radii and lengths. The effects of the structural parameters of ACND on the localized surface plasmon resonance (LSPR) mode are also studied. Results show two resonance peaks in the extinction spectra of ACND: the higher-energy anti-bonding mode and the lower-energy bonding mode. The interaction of two hybridization plasmonic resonance modes produces an asymmetric line shape in the extinction spectra, which is considered to be a Fano resonance profile.

  14. Reflection-phase spectra of cavity-resonator-integrated guided-mode resonance devices

    NASA Astrophysics Data System (ADS)

    Inoue, Junichi; Okuda, Hiroki; Kintaka, Kenji; Nishio, Kenzo; Ura, Shogo

    2017-07-01

    A cavity-resonator-integrated guided-mode resonance filter (CRIGF) consisting of waveguide gratings on a transparent substrate can provide not only a narrowband reflection spectrum but also a steep reflection-phase spectrum. Reflection-phase spectra of CRIGFs were discussed in detail theoretically with an analytical expression. It was found that CRIGFs can be categorized into two types showing a phase variation of 2π rad, namely, reflection-phase rotation, or no rotation. On the other hand, the same structure on a high-reflection mirror, instead of the transparent substrate, normally shows the rotation. The two types of CRIGFs were designed and fabricated with different core thicknesses so that theoretically predicted reflection-phase characteristics with and without rotation could be demonstrated experimentally.

  15. Temperature peaking at beginning of breakdown in 2.45 GHz pulsed off-resonance electron cyclotron resonance ion source hydrogen plasma

    NASA Astrophysics Data System (ADS)

    Cortázar, O. D.; Megía-Macías, A.; Vizcaíno-de-Julián, A.

    2012-10-01

    An experimental study of temperature and density evolution during breakdown in off-resonance ECR hydrogen plasma is presented. Under square 2.45 GHz microwave excitation pulses with a frequency of 50 Hz and relative high microwave power, unexpected transient temperature peaks that reach 18 eV during 20 μs are reported at very beginning of plasma breakdown. Decays of such peaks reach final stable temperatures of 5 eV at flat top microwave excitation pulse. Evidence of interplay between incoming power and duty cycle giving different kind of plasma parameters evolutions engaged to microwave coupling times is observed. Under relative high power conditions where short microwave coupling times are recorded, high temperature peaks are measured. However, for lower incoming powers and longer coupling times, temperature evolves gradually to a higher final temperature without peaking. On the other hand, the early instant where temperature peaks are observed also suggest a possible connection with preglow processes during breakdown in ECRIS plasmas.

  16. Temperature peaking at beginning of breakdown in 2.45 GHz pulsed off-resonance electron cyclotron resonance ion source hydrogen plasma

    SciTech Connect

    Cortazar, O. D.

    2012-10-15

    An experimental study of temperature and density evolution during breakdown in off-resonance ECR hydrogen plasma is presented. Under square 2.45 GHz microwave excitation pulses with a frequency of 50 Hz and relative high microwave power, unexpected transient temperature peaks that reach 18 eV during 20 {mu}s are reported at very beginning of plasma breakdown. Decays of such peaks reach final stable temperatures of 5 eV at flat top microwave excitation pulse. Evidence of interplay between incoming power and duty cycle giving different kind of plasma parameters evolutions engaged to microwave coupling times is observed. Under relative high power conditions where short microwave coupling times are recorded, high temperature peaks are measured. However, for lower incoming powers and longer coupling times, temperature evolves gradually to a higher final temperature without peaking. On the other hand, the early instant where temperature peaks are observed also suggest a possible connection with preglow processes during breakdown in ECRIS plasmas.

  17. Temperature peaking at beginning of breakdown in 2.45 GHz pulsed off-resonance electron cyclotron resonance ion source hydrogen plasma.

    PubMed

    Cortázar, O D; Megía-Macías, A; Vizcaíno-de-Julián, A

    2012-10-01

    An experimental study of temperature and density evolution during breakdown in off-resonance ECR hydrogen plasma is presented. Under square 2.45 GHz microwave excitation pulses with a frequency of 50 Hz and relative high microwave power, unexpected transient temperature peaks that reach 18 eV during 20 μs are reported at very beginning of plasma breakdown. Decays of such peaks reach final stable temperatures of 5 eV at flat top microwave excitation pulse. Evidence of interplay between incoming power and duty cycle giving different kind of plasma parameters evolutions engaged to microwave coupling times is observed. Under relative high power conditions where short microwave coupling times are recorded, high temperature peaks are measured. However, for lower incoming powers and longer coupling times, temperature evolves gradually to a higher final temperature without peaking. On the other hand, the early instant where temperature peaks are observed also suggest a possible connection with preglow processes during breakdown in ECRIS plasmas.

  18. Silicon photonics WDM interconnects based on resonant ring modulators and semiconductor mode locked laser

    NASA Astrophysics Data System (ADS)

    Müller, J.; Hauck, J.; Shen, B.; Romero-García, S.; Islamova, E.; Sharif Azadeh, S.; Joshi, S.; Chimot, N.; Moscoso-Mártir, A.; Merget, F.; Lelarge, F.; Witzens, J.

    2015-03-01

    We demonstrate wavelength domain multiplexed (WDM) data transmission with a data rate of 14 Gbps based on optical carrier generation with a single-section semiconductor mode-locked laser (SS-MLL) and modulation with a Silicon Photonics (SiP) resonant ring modulator (RRM). 18 channels are sequentially measured, whereas the best recorded eye diagrams feature signal quality factors (Q-factors) above 7. While optical re-amplification was necessary to maintain the link budgets and therefore system measurements were performed with an erbium doped fiber amplifier (EDFA), preliminary characterization done with a semiconductor optical amplifier (SOA) indicates compatibility with the latter pending the integration of an additional optical filter to select a subset of carriers and prevent SOA saturation. A systematic analysis of the relative intensity noise (RIN) of isolated comb lines and of signal Q-factors indicates that the link is primarily limited by amplified spontaneous emission (ASE) from the EDFA rather than laser RIN. Measured RIN for single comb components is below -120 dBc/Hz in the range from 7 MHz to 4 GHz and drops to the shot noise level at higher frequencies.

  19. Real-time synchronous imaging of electromechanical resonator mode and equilibrium profiles.

    PubMed

    Linzon, Y; Krylov, S; Ilic, B; Southworth, D R; Barton, R A; Cipriany, B R; Cross, J D; Parpia, J M; Craighead, H G

    2010-08-01

    Interferometric imaging of normal mode dynamics in electromechanical resonators, oscillating in the rf regime, is demonstrated by synchronous imaging with a pulsed nanosecond laser. Profiles of mechanical modes in suspended thin film structures and their equilibrium profiles are measured through all-optical Fabry-Perot reflectance fits to the temporal traces. As a proof of principle, the mode patterns of a microdrum silicon resonator are visualized, and the extracted vibration modes and equilibrium profile show good agreement with numerical estimations.

  20. A versatile and modular quasi optics-based 200GHz dual dynamic nuclear polarization and electron paramagnetic resonance instrument.

    PubMed

    Siaw, Ting Ann; Leavesley, Alisa; Lund, Alicia; Kaminker, Ilia; Han, Songi

    2016-03-01

    Solid-state dynamic nuclear polarization (DNP) at higher magnetic fields (>3T) and cryogenic temperatures (∼ 2-90K) has gained enormous interest and seen major technological advances as an NMR signal enhancing technique. Still, the current state of the art DNP operation is not at a state at which sample and freezing conditions can be rationally chosen and the DNP performance predicted a priori, but relies on purely empirical approaches. An important step towards rational optimization of DNP conditions is to have access to DNP instrumental capabilities to diagnose DNP performance and elucidate DNP mechanisms. The desired diagnoses include the measurement of the "DNP power curve", i.e. the microwave (MW) power dependence of DNP enhancement, the "DNP spectrum", i.e. the MW frequency dependence of DNP enhancement, the electron paramagnetic resonance (EPR) spectrum, and the saturation and spectral diffusion properties of the EPR spectrum upon prolonged MW irradiation typical of continuous wave (CW) DNP, as well as various electron and nuclear spin relaxation parameters. Even basic measurements of these DNP parameters require versatile instrumentation at high magnetic fields not commercially available to date. In this article, we describe the detailed design of such a DNP instrument, powered by a solid-state MW source that is tunable between 193 and 201 GHz and outputs up to 140 mW of MW power. The quality and pathway of the transmitted and reflected MWs is controlled by a quasi-optics (QO) bridge and a corrugated waveguide, where the latter couples the MW from an open-space QO bridge to the sample located inside the superconducting magnet and vice versa. Crucially, the versatility of the solid-state MW source enables the automated acquisition of frequency swept DNP spectra, DNP power curves, the diagnosis of MW power and transmission, and frequency swept continuous wave (CW) and pulsed EPR experiments. The flexibility of the DNP instrument centered around the QO MW

  1. A versatile and modular quasi optics-based 200 GHz dual dynamic nuclear polarization and electron paramagnetic resonance instrument

    NASA Astrophysics Data System (ADS)

    Siaw, Ting Ann; Leavesley, Alisa; Lund, Alicia; Kaminker, Ilia; Han, Songi

    2016-03-01

    Solid-state dynamic nuclear polarization (DNP) at higher magnetic fields (>3 T) and cryogenic temperatures (∼2-90 K) has gained enormous interest and seen major technological advances as an NMR signal enhancing technique. Still, the current state of the art DNP operation is not at a state at which sample and freezing conditions can be rationally chosen and the DNP performance predicted a priori, but relies on purely empirical approaches. An important step towards rational optimization of DNP conditions is to have access to DNP instrumental capabilities to diagnose DNP performance and elucidate DNP mechanisms. The desired diagnoses include the measurement of the "DNP power curve", i.e. the microwave (MW) power dependence of DNP enhancement, the "DNP spectrum", i.e. the MW frequency dependence of DNP enhancement, the electron paramagnetic resonance (EPR) spectrum, and the saturation and spectral diffusion properties of the EPR spectrum upon prolonged MW irradiation typical of continuous wave (CW) DNP, as well as various electron and nuclear spin relaxation parameters. Even basic measurements of these DNP parameters require versatile instrumentation at high magnetic fields not commercially available to date. In this article, we describe the detailed design of such a DNP instrument, powered by a solid-state MW source that is tunable between 193 and 201 GHz and outputs up to 140 mW of MW power. The quality and pathway of the transmitted and reflected MWs is controlled by a quasi-optics (QO) bridge and a corrugated waveguide, where the latter couples the MW from an open-space QO bridge to the sample located inside the superconducting magnet and vice versa. Crucially, the versatility of the solid-state MW source enables the automated acquisition of frequency swept DNP spectra, DNP power curves, the diagnosis of MW power and transmission, and frequency swept continuous wave (CW) and pulsed EPR experiments. The flexibility of the DNP instrument centered around the QO MW

  2. A versatile and modular quasi optics-based 200 GHz dual dynamic nuclear polarization and electron paramagnetic resonance instrument

    PubMed Central

    Siaw, Ting Ann; Leavesley, Alisa; Lund, Alicia; Kaminker, Ilia; Han, Songi

    2016-01-01

    Solid-state dynamic nuclear polarization (DNP) at higher magnetic fields (>3 T) and cryogenic temperatures (~2–90 K) has gained enormous interest and seen major technological advances as an NMR signal enhancing technique. Still, the current state of the art DNP operation is not at a state at which sample and freezing conditions can be rationally chosen and the DNP performance predicted a priori, but relies on purely empirical approaches. An important step towards rational optimization of DNP conditions is to have access to DNP instrumental capabilities to diagnose DNP performance and elucidate DNP mechanisms. The desired diagnoses include the measurement of the “DNP power curve”, i.e. the microwave (MW) power dependence of DNP enhancement, the “DNP spectrum”, i.e. the MW frequency dependence of DNP enhancement, the electron paramagnetic resonance (EPR) spectrum and the saturation and spectral diffusion properties of the EPR spectrum upon prolonged MW irradiation typical of continuous wave (CW) DNP, as well as various electron and nuclear spin relaxation parameters. Even basic measurements of these DNP parameters require versatile instrumentation at high magnetic fields not commercially available to date. In this article, we describe the detailed design of such a DNP instrument, powered by a solid-state MW source that is tunable between 193 – 201 GHz and outputs up to 140 mW of MW power. The quality and pathway of the transmitted and reflected MWs is controlled by a quasi-optics (QO) bridge and a corrugated waveguide, where the latter couples the MW from an open-space QO bridge to the sample located inside the superconducting magnet and vice versa. Crucially, the versatility of the solid-state MW source enables the automated acquisition of frequency swept DNP spectra, DNP power curves, the diagnosis of MW power and transmission, and frequency swept continuous wave (CW) and pulsed EPR experiments. The flexibility of the DNP instrument centered around the

  3. Thermal magnetic resonance: physics considerations and electromagnetic field simulations up to 23.5 Tesla (1GHz).

    PubMed

    Winter, Lukas; Oezerdem, Celal; Hoffmann, Werner; van de Lindt, Tessa; Periquito, Joao; Ji, Yiyi; Ghadjar, Pirus; Budach, Volker; Wust, Peter; Niendorf, Thoralf

    2015-09-22

    Glioblastoma multiforme is the most common and most aggressive malign brain tumor. The 5-year survival rate after tumor resection and adjuvant chemoradiation is only 10 %, with almost all recurrences occurring in the initially treated site. Attempts to improve local control using a higher radiation dose were not successful so that alternative additive treatments are urgently needed. Given the strong rationale for hyperthermia as part of a multimodal treatment for patients with glioblastoma, non-invasive radio frequency (RF) hyperthermia might significantly improve treatment results. A non-invasive applicator was constructed utilizing the magnetic resonance (MR) spin excitation frequency for controlled RF hyperthermia and MR imaging in an integrated system, which we refer to as thermal MR. Applicator designs at RF frequencies 300 MHz, 500 MHz and 1GHz were investigated and examined for absolute applicable thermal dose and temperature hotspot size. Electromagnetic field (EMF) and temperature simulations were performed in human voxel models. RF heating experiments were conducted at 300 MHz and 500 MHz to characterize the applicator performance and validate the simulations. The feasibility of thermal MR was demonstrated at 7.0 T. The temperature could be increased by ~11 °C in 3 min in the center of a head sized phantom. Modification of the RF phases allowed steering of a temperature hotspot to a deliberately selected location. RF heating was monitored using the integrated system for MR thermometry and high spatial resolution MRI. EMF and thermal simulations demonstrated that local RF hyperthermia using the integrated system is feasible to reach a maximum temperature in the center of the human brain of 46.8 °C after 3 min of RF heating while surface temperatures stayed below 41 °C. Using higher RF frequencies reduces the size of the temperature hotspot significantly. The opportunities and capabilities of thermal magnetic resonance for RF hyperthermia

  4. The influence of the whispering gallery modes resonators shape on their sensitivity to the movement

    NASA Astrophysics Data System (ADS)

    Filatov, Yuri V.; Govorenko, Ekaterina V.; Kukaev, Alexander S.; Shalymov, Egor V.; Venediktov, Vladimir Yu.

    2017-05-01

    The optical whispering gallery modes resonators are axially symmetrical resonators with smooth edges, supporting the existence of the whispering gallery modes by the total internal reflection on the surface of the resonator. For today various types of such resonators were developed, namely the ball-shaped, tor-shaped, bottle-shaped, disk-shaped etc. The movement of whispering gallery modes resonators in inertial space causes the changes of their shape. The result is a spectral shift of the whispering gallery modes. Optical methods allow to register this shift with high precision. It can be used in particular for the measurement of angular velocities in inertial orientation and navigation systems. However, different types of resonators react to the movement on a miscellaneous. In addition, their sensitivity to movement can be changed when changing the geometric parameters of these resonators. This work is devoted to a research of these aspects.

  5. Excitation of ultrasharp trapped-mode resonances in mirror-symmetric metamaterials

    NASA Astrophysics Data System (ADS)

    Yang, Shengyan; Liu, Zhe; Xia, Xiaoxiang; E, Yiwen; Tang, Chengchun; Wang, Yujin; Li, Junjie; Wang, Li; Gu, Changzhi

    2016-06-01

    We experimentally demonstrate a metamaterial structure composed of two mirror-symmetric joint split ring resonators (JSRRs) that support extremely sharp trapped-mode resonance with a large modulation depth in the terahertz region. Contrary to the regular mirror-arranged SRR arrays in which both the subradiant inductive-capacitive (LC) resonance and quadrupole-mode resonance can be excited, our designed structure features a metallic microstrip bridging the adjacent SRRs, which leads to the emergence of an otherwise inaccessible ultrahigh-quality-factor resonance. The ultrasharp resonance occurs near the Wood-Rayleigh anomaly frequency, and the underlying mechanism can be attributed to the strong coupling between the in-plane propagating collective lattice surface mode originating from the array periodicity and localized surface plasmon resonance in mirror-symmetric coupled JSRRs, which dramatically reduces radiative damping. The ultrasharp resonance shows great potential for multifunctional applications such as plasmonic switching, low-power nonlinear processing, and chemical and biological sensing.

  6. GHz nuclear magnetic resonance

    SciTech Connect

    Cross, T.A.; Drobny, G.; Trewhella, J.

    1994-12-01

    For the past dozen years, 500- and 600-MHz spectrometers have become available in many laboratories. The first 600-MHz NMR spectrometer (at Carnegie Mellon University) was commissioned more than 15 years ago and, until 1994, represented the highest field available for high-resolution NMR. This year, we have witnessed unprecedented progress in the development of very high field magnets for NMR spectroscopy, including the delivery of the first commercial 750-MHz NMR spectrometers. In addition, NMR signals have been obtained from 20-Tesla magnets (850 MHz for {sup 1}H`s) at both Los Alamos National Laboratory and Florida State University in the NHMFL (National High Magnetic Field Laboratory). These preliminary experiments have been performed in magnets with 100-ppm homogeneity, but a 20-Tesla magnet developed for the NHMFL will be brought to field this year with a projected homogeneity of 0.1 ppm over a 1-cm-diam spherical volume.

  7. Cylindrical vector resonant modes achieved in planar photonic crystal cavities with enlarged air-holes

    NASA Astrophysics Data System (ADS)

    Chang, Kang; Fang, Liang; Zhao, Chenyang; Zhao, Jianlin; Gan, Xuetao

    2017-09-01

    We reveal a triangular-lattice planar photonic crystal supports Bloch modes with radially and azimuthally symmetric electric field distributions at the top band-edge of the first photonic band. Bifurcated from the corresponding Bloch modes, two cylindrical vector resonant modes are achieved by simply enlarging the central air-hole of the planar photonic crystal, which have high quality factors around 3,000 and small mode volume. The far-field radiations of the two resonant modes present high-quality cylindrical vector beam profiles. The resonant modes could be optimized by modifying the six nearest neighboring air-holes around the central defect. The cylindrically symmetric characteristics of the resonant mode's near- and far-fields might provide a new view to investigate light-matter interactions and device developments in planar photonic crystal cavities.

  8. Electrodynamics and radiofrequency antenna concepts for human magnetic resonance at 23.5 T (1 GHz) and beyond.

    PubMed

    Winter, Lukas; Niendorf, Thoralf

    2016-06-01

    This work investigates electrodynamic constraints, explores RF antenna concepts and examines the transmission fields (B 1 (+) ) and RF power deposition of dipole antenna arrays for (1)H magnetic resonance of the human brain at 1 GHz (23.5 T). Electromagnetic field (EMF) simulations are performed in phantoms with average tissue simulants for dipole antennae using discrete frequencies [300 MHz (7.0 T) to 3 GHz (70.0 T)]. To advance to a human setup EMF simulations are conducted in anatomical human voxel models of the human head using a 20-element dipole array operating at 1 GHz. Our results demonstrate that transmission fields suitable for (1)H MR of the human brain can be achieved at 1 GHz. An increase in transmit channel density around the human head helps to enhance B 1 (+) in the center of the brain. The calculated relative increase in specific absorption rate at 23.5 versus 7.0 T was below 1.4 (in-phase phase setting) and 2.7 (circular polarized phase setting) for the dipole antennae array. The benefits of multi-channel dipole antennae at higher frequencies render MR at 23.5 T feasible from an electrodynamic standpoint. This very preliminary finding opens the door on further explorations that might be catalyzed into a 20-T class human MR system.

  9. Coupled mode parametric resonance in a vibrating screen model

    NASA Astrophysics Data System (ADS)

    Slepyan, Leonid I.; Slepyan, Victor I.

    2014-02-01

    We consider a simple dynamic model of the vibrating screen operating in the parametric resonance (PR) mode. This model was used in the course of designing and setting of such a screen in LPMC. The PR-based screen compares favorably with conventional types of such machines, where the transverse oscillations are excited directly. It is characterized by larger values of the amplitude and by insensitivity to damping in a rather wide range. The model represents an initially strained system of two equal masses connected by a linearly elastic string. Self-equilibrated, longitudinal, harmonic forces act on the masses. Under certain conditions this results in transverse, finite-amplitude oscillations of the string. The problem is reduced to a system of two ordinary differential equations coupled by the geometric nonlinearity. Damping in both the transverse and longitudinal oscillations is taken into account. Free and forced oscillations of this mass-string system are examined analytically and numerically. The energy exchange between the longitudinal and transverse modes of free oscillations is demonstrated. An exact analytical solution is found for the forced oscillations, where the coupling plays the role of a stabilizer. In a more general case, the harmonic analysis is used with neglect of the higher harmonics. Explicit expressions for all parameters of the steady nonlinear oscillations are determined. The domains are found where the analytically obtained steady oscillation regimes are stable. Over the frequency ranges, where the steady oscillations exist, a perfect correspondence is found between the amplitudes obtained analytically and numerically. Illustrations based on the analytical and numerical simulations are presented.

  10. Resonant absorption in semiconductor nanowires and nanowire arrays: Relating leaky waveguide modes to Bloch photonic crystal modes

    SciTech Connect

    Fountaine, Katherine T.; Whitney, William S.; Atwater, Harry A.

    2014-10-21

    We present a unified framework for resonant absorption in periodic arrays of high index semiconductor nanowires that combines a leaky waveguide theory perspective and that of photonic crystals supporting Bloch modes, as array density transitions from sparse to dense. Full dispersion relations are calculated for each mode at varying illumination angles using the eigenvalue equation for leaky waveguide modes of an infinite dielectric cylinder. The dispersion relations along with symmetry arguments explain the selectivity of mode excitation and spectral red-shifting of absorption for illumination parallel to the nanowire axis in comparison to perpendicular illumination. Analysis of photonic crystal band dispersion for varying array density illustrates that the modes responsible for resonant nanowire absorption emerge from the leaky waveguide modes.

  11. Resonant magnetic perturbation effect on tearing mode dynamics

    NASA Astrophysics Data System (ADS)

    Frassinetti, L.; Olofsson, K. E. J.; Brunsell, P. R.; Drake, J. R.

    2010-03-01

    The effect of a resonant magnetic perturbation (RMP) on the tearing mode (TM) dynamics is experimentally studied in the EXTRAP T2R device. EXTRAP T2R is equipped with a set of sensor coils and active coils connected by a digital controller allowing a feedback control of the magnetic instabilities. The recently upgraded feedback algorithm allows the suppression of all the error field harmonics but keeping a selected harmonic to the desired amplitude, therefore opening the possibility of a clear study of the RMP effect on the corresponding TM. The paper shows that the RMP produces two typical effects: (1) a weak oscillation in the TM amplitude and a modulation in the TM velocity or (2) a strong modulation in the TM amplitude and phase jumps. Moreover, the locking mechanism of a TM to a RMP is studied in detail. It is shown that before the locking, the TM dynamics is characterized by velocity modulation followed by phase jumps. Experimental results are reasonably explained by simulations obtained with a model.

  12. A review: aluminum nitride MEMS contour-mode resonator

    NASA Astrophysics Data System (ADS)

    Yunhong, Hou; Meng, Zhang; Guowei, Han; Chaowei, Si; Yongmei, Zhao; Jin, Ning

    2016-10-01

    Over the past several decades, the technology of micro-electromechanical system (MEMS) has advanced. A clear need of miniaturization and integration of electronics components has had new solutions for the next generation of wireless communications. The aluminum nitride (AlN) MEMS contour-mode resonator (CMR) has emerged and become promising and competitive due to the advantages of the small size, high quality factor and frequency, low resistance, compatibility with integrated circuit (IC) technology, and the ability of integrating multi-frequency devices on a single chip. In this article, a comprehensive review of AlN MEMS CMR technology will be presented, including its basic working principle, main structures, fabrication processes, and methods of performance optimization. Among these, the deposition and etching process of the AlN film will be specially emphasized and recent advances in various performance optimization methods of the CMR will be given through specific examples which are mainly focused on temperature compensation and reducing anchor losses. This review will conclude with an assessment of the challenges and future trends of the CMR. Project supported by National Natural Science Foundation (Nos. 61274001, 61234007, 61504130), the Nurturing and Development Special Projects of Beijing Science and Technology Innovation Base's Financial Support (No. Z131103002813070), and the National Defense Science and Technology Innovation Fund of CAS (No. CXJJ-14-M32).

  13. Protein-based flexible whispering gallery mode resonators

    NASA Astrophysics Data System (ADS)

    Yilmaz, Huzeyfe; Pena-Francesch, Abdon; Xu, Linhua; Shreiner, Robert; Jung, Huihun; Huang, Steven H.; Özdemir, Sahin K.; Demirel, Melik C.; Yang, Lan

    2016-02-01

    The idea of creating photonics tools for sensing, imaging and material characterization has long been pursued and many achievements have been made. Approaching the level of solutions provided by nature however is hindered by routine choice of materials. To this end recent years have witnessed a great effort to engineer mechanically flexible photonic devices using polymer substrates. On the other hand, biodegradability and biocompatibility still remains to be incorporated. Hence biomimetics holds the key to overcome the limitations of traditional materials in photonics design. Natural proteins such as sucker ring teeth (SRT) and silk for instance have remarkable mechanical and optical properties that exceed the endeavors of most synthetic and natural polymers. Here we demonstrate for the first time, toroidal whispering gallery mode resonators (WGMR) fabricated entirely from protein structures such as SRT of Loligo vulgaris (European squid) and silk from Bombyx mori. We provide here complete optical and material characterization of proteinaceous WGMRs, revealing high quality factors in microscale and enhancement of Raman signatures by a microcavity. We also present a most simple application of a WGMR as a natural protein add-drop filter, made of SRT protein. Our work shows that with protein-based materials, optical, mechanical and thermal properties can be devised at the molecular level and it lays the groundwork for future eco-friendly, flexible photonics device design.

  14. On the fundamental mode of the optical resonator with toroidal mirrors

    SciTech Connect

    Serednyakov, S.S.; Vinokurov, N.A.

    1995-12-31

    The fundamental mode of the optical resonator with the toroidal mirrors is investigated. The losses in such resonator with the on-axis holes are low in compare with the case of spherical mirrors. The use of this type of optical resonator is briefly discussed.

  15. Interactions between directly- and parametrically-driven vibration modes in a micromechanical resonator

    NASA Astrophysics Data System (ADS)

    Westra, H. J. R.; Karabacak, D. M.; Brongersma, S. H.; Crego-Calama, M.; van der Zant, H. S. J.; Venstra, W. J.

    2011-10-01

    The interactions between parametrically- and directly-driven vibration modes of a clamped-clamped beam resonator are studied. An integrated piezoelectric transducer is used for direct and parametric excitation. First, the parametric amplification and oscillation of a single mode are analyzed by the power and phase dependence below and above the threshold for parametric oscillation. Then, the motion of a parametrically-driven mode is detected by the induced change in resonance frequency in another mode of the same resonator. The resonance frequency shift is the result of the nonlinear coupling between the modes by the displacement-induced tension in the beam. These nonlinear modal interactions result in the quadratic relation between the resonance frequency of one mode and the amplitude of another mode. The amplitude of a parametrically-oscillating mode depends on the square root of the pump frequency. Combining these dependencies yields a linear relation between the resonance frequency of the directly-driven mode and the frequency of the parametrically-oscillating mode.

  16. In-fiber whispering-gallery-mode resonator fabricated by femtosecond laser micromachining.

    PubMed

    Shi, Leilei; Zhu, Tao; Huang, Dongmei; Liu, Min; Deng, Ming; Huang, Wei

    2015-08-15

    An in-fiber whispering-gallery-mode resonator fabricated by femtosecond laser micromachining is demonstrated. The cylinder resonator cavity is fabricated by scanning the D-fiber cladding with infrared femtosecond pulses along a cylindrical trace with a radius of 25 μm and height of 20 μm. Quality factor on the order of 10(3) is achieved by smoothing the cavity surface with an ultrasonic cleaner, which is mainly limited by the surface roughness of several hundred nanometers. Resonant characteristics and polarization dependence of the proposed resonator are also studied in detail. Our method takes a step forward in the integration of whispering-gallery-mode resonators.

  17. The VLA-COSMOS 3 GHz Large Project: Cosmic evolution of radio AGN and implications for radio-mode feedback since z 5

    NASA Astrophysics Data System (ADS)

    Smolčić, V.; Novak, M.; Delvecchio, I.; Ceraj, L.; Bondi, M.; Delhaize, J.; Marchesi, S.; Murphy, E.; Schinnerer, E.; Vardoulaki, E.; Zamorani, G.

    2017-06-01

    Based on a sample of over 1800 radio AGN at redshifts out to z 5, which have typical stellar masses within 3 × (1010 - 1011)M⊙, and 3 GHz radio data in the COSMOS field, we derived the 1.4 GHz radio luminosity functions for radio AGN (L1.4 GHz 1022 - 1027 W Hz-1) out to z 5. We constrained the evolution of this population via continuous models of pure density and pure luminosity evolutions, and we found best-fit parametrizations of Φ∗ ∝ (1 + z)(2.00 ± 0.18) - (0.60 ± 0.14)z, and L∗ ∝ (1 + z)(2.88 ± 0.82) - (0.84 ± 0.34)z, respectively, with a turnover in number and luminosity densities of the population at z ≈ 1.5. We converted 1.4 GHz luminosity to kinetic luminosity taking uncertainties of the scaling relation used into account. We thereby derived the cosmic evolution of the kinetic luminosity density provided by the AGN and compared this luminosity density to the radio-mode AGN feedback assumed in the Semi-Analytic Galaxy Evolution (SAGE) model, i.e., to the redshift evolution of the central supermassive black hole accretion luminosity taken in the model as the source of heating that offsets the energy losses of the cooling, hot halo gas, and thereby limits further stellar mass growth of massive galaxies. We find that the kinetic luminosity exerted by our radio AGN may be high enough to balance the radiative cooling of the hot gas at each cosmic epoch since z 5. However, although our findings support the idea of radio-mode AGN feedback as a cosmologically relevant process in massive galaxy formation, many simplifications in both the observational and semi-analytic approaches still remain and need to be resolved before robust conclusions can be reached.

  18. Higher order mode of a microstripline fed cylindrical dielectric resonator antenna

    NASA Astrophysics Data System (ADS)

    Kumar, A. V. Praveen

    2016-03-01

    A microstrip transmission line can be used to excite the broadside radiating mode of a cylindrical dielectric resonator antenna (CDRA). The same is found to excite considerably well a higher order mode (HOM) as well. However unlike the broadside mode, the higher order mode gives distorted radiation pattern which makes this mode less useful for practical applications. The cause of distortion in the HOM radiation and the dependence of HOM coupling on the microstrip feed line are explored using HFSS simulations.

  19. Higher order mode of a microstripline fed cylindrical dielectric resonator antenna

    SciTech Connect

    Kumar, A. V. Praveen

    2016-03-09

    A microstrip transmission line can be used to excite the broadside radiating mode of a cylindrical dielectric resonator antenna (CDRA). The same is found to excite considerably well a higher order mode (HOM) as well. However unlike the broadside mode, the higher order mode gives distorted radiation pattern which makes this mode less useful for practical applications. The cause of distortion in the HOM radiation and the dependence of HOM coupling on the microstrip feed line are explored using HFSS simulations.

  20. Theory of light-induced resonances with collective Higgs and Leggett modes in multiband superconductors

    NASA Astrophysics Data System (ADS)

    Murotani, Yuta; Tsuji, Naoto; Aoki, Hideo

    2017-03-01

    We theoretically investigate coherent optical excitations of collective modes in two-band BCS superconductors, which accommodate two Higgs modes and one Leggett mode corresponding, respectively, to the amplitude and relative-phase oscillations of the superconducting order parameters associated with the two bands. We find, based on a mean-field analysis, that each collective mode can be resonantly excited through a nonlinear light-matter coupling when the doubled frequency of the driving field coincides with the frequency of the corresponding mode. Among the two Higgs modes, the higher-energy one exhibits a sharp resonance with light, while the lower-energy mode has a broadened resonance width. The Leggett mode is found to be resonantly induced by a homogeneous ac electric field because the leading nonlinear effect generates a potential offset between the two bands that couples to the relative phase of the order parameters. The resonance for the Leggett mode becomes sharper with increasing temperature. All of these light-induced collective modes along with density fluctuations contribute to the third-harmonic generation. We also predict an experimental possibility of optical detection of the Leggett mode.

  1. Resonant generation of topological modes in trapped Bose-Einstein gases

    SciTech Connect

    Yukalov, V.I.; Marzlin, K.-P.; Yukalova, E.P.

    2004-02-01

    Trapped atoms cooled down to temperatures below the Bose-Einstein condensation temperature are considered. Stationary solutions to the Gross-Pitaevskii equation (GPE) define the topological coherent modes, representing nonground-state Bose-Einstein condensates. These modes can be generated by means of alternating fields whose frequencies are in resonance with the transition frequencies between two collective energy levels corresponding to two different topological modes. The theory of resonant generation of these modes is generalized in several aspects: Multiple-mode formation is described; a shape-conservation criterion is derived, imposing restrictions on the admissible spatial dependence of resonant fields; evolution equations for the case of three coherent modes are investigated; the complete stability analysis is accomplished; the effects of harmonic generation and parametric conversion for the topological coherent modes are predicted. All considerations are realized both by employing approximate analytical methods as well as by numerically solving the GPE. Numerical solutions confirm all conclusions following from analytical methods.

  2. Observation of three-mode parametric instability in a micromechanical resonator

    NASA Astrophysics Data System (ADS)

    Ganesan, Adarsh; Do, Cuong; Seshia, Ashwin

    2016-11-01

    We present systematic experimental observations of three-mode auto-parametric instability in a micromechanical resonator analogous to previous experimental observations of this effect in optical parametric resonators. The three-mode instability is triggered when a driven mode at frequency ωd couples to two lower frequency modes (frequencies ω1 and ω2) such that ωd = ω1+ω2. Similar to the 2 mode instability, the phenomenon is seen to be threshold dependent and sensitive to driving conditions and system parameters. In support of the experimental observations, a dynamical model has also been specified.

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

    NASA Astrophysics Data System (ADS)

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

    2017-06-01

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

  4. Room temperature sputtering of inclined c-axis ZnO for shear mode solidly mounted resonators

    NASA Astrophysics Data System (ADS)

    Rughoobur, G.; DeMiguel-Ramos, M.; Mirea, T.; Clement, M.; Olivares, J.; Díaz-Durán, B.; Sangrador, J.; Miele, I.; Milne, W. I.; Iborra, E.; Flewitt, A. J.

    2016-01-01

    ZnO films with a c-axis significantly inclined away from the surface normal were grown by a remote plasma sputtering technique at room temperature. The films were used to make solidly mounted resonators (SMRs) operating in shear mode at a resonant frequency of 1.35 GHz. Control of the ZnO microstructure was achieved using a polycrystalline AlN seed layer which can be added on top of a sputtered acoustic mirror to give a complete SMR device. The ZnO was reactively sputtered in an atmosphere of argon and oxygen from a zinc target. The c-axis of the ZnO was estimated to be at an angle of ˜45° to the surface normal. SMRs were measured to have quality factors (Q) of up to 140 and effective electromechanical coupling coefficients of up to 2.2% in air. Although an inclined c-axis can be achieved with direct growth onto the acoustic mirror, it is shown that the AlN seed layer provides higher coupling coefficients and narrower inclination angular distribution. The responses of the devices in liquids of different viscosities (acetone, water, and AZ5214E photoresist) were measured. The shear mode Q decreased by 45% in acetone, 72% in water, and 92% in AZ5214E.

  5. Hyper-Parametric Oscillations in a Whispering Gallery Mode Fluorite Resonator

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy; Strekalov, Dmitry; Mohageg, Makan; Ilchenko, Vladimir; Matsko, Andrey; Maleki, Lute

    2004-01-01

    This viewgraph presentation summarizes the hyper-parametric oscillations observations of the fluorite resonator. The reporters have observed various nonlinear effects in ultra-high Q crystalline whispering gallery mode (WGM) resonators. In particular, it was demonstrated a low threshold optical hyper-parametric oscillations in a high-Q (Q=1010) CaF2 WGM resonator. The oscillations result from the resonantly enhanced four-wave-mixing occurring due to Kerr nonlinearity of the material.

  6. Guided-mode-resonance coupled localized surface plasmons for dually resonance enhanced Raman scattering sensing

    NASA Astrophysics Data System (ADS)

    Wang, Zheng; Liu, Chao; Li, Erwen; Chakravarty, Swapnajit; Xu, Xiaochuan; Wang, Alan X.; Fan, D. L.; Chen, Ray T.

    2017-02-01

    Raman scattering spectroscopy is a unique tool to probe vibrational, rotational, and other low-frequency modes of a molecular system and therefore could be utilized to identify chemistry and quantity of molecules. However, the ultralow efficient Raman scattering, which is only 1/109 1/1014 of the excitation light due to the small Raman scattering cross-sections of molecules, have significantly hindered its development in practical sensing applications. The discovery of surface-enhanced Raman scattering (SERS) in the 1970s and the significant progress in nanofabrication technique, provide a promising solution to overcome the inherent issues of Raman spectroscopy. It is found that In the vicinity of nanoparticles and their junctions, the Raman signals of molecules can be significantly improved by an enhancement factor as high as 1010, due to the ultrahigh electric field generated by the localized surface plasmons resonance (LSPR), where the intensity of Raman scattering is proportional to the |E|4. In this work, we propose and demonstrate a new approach combining LSPR from nanocapsules with densely assembled silver nanoparticles (NC-AgNPs) and guidemode- resonance (GMR) from dielectric photonic crystal slabs (PCSs) for SERS substrates with robustly high performance.

  7. Investigation of ELM [edge localized mode] Dynamics with the Resonant Magnetic Perturbation Effects

    SciTech Connect

    Pankin, Alexei Y.; Kritz, Arnold H.

    2011-07-19

    Topics covered are: anomalous transport and E x B flow shear effects in the H-mode pedestal; RMP (resonant magnetic perturbation) effects in NSTX discharges; development of a scaling of H-mode pedestal in tokamak plasmas with type I ELMs (edge localized modes); and divertor heat load studies.

  8. Observation of mode conversion of m = minus 1 fast waves on the Alfven resonance layer

    SciTech Connect

    Amagishi, Y. )

    1990-03-12

    Fast waves or MHD surface waves of {ital m}={minus}1 (poloidal mode number of left-hand rotation) have been observed to be mode converted on the Alfven resonance layer. The converted waves are a quasielectrostatic form of the shear Alfven waves, i.e., kinetic Alfven wave and/or the resistive mode.

  9. A novel vibration mode testing method for cylindrical resonators based on microphones.

    PubMed

    Zhang, Yongmeng; Wu, Yulie; Wu, Xuezhong; Xi, Xiang; Wang, Jianqiu

    2015-01-16

    Non-contact testing is an important method for the study of the vibrating characteristic of cylindrical resonators. For the vibratory cylinder gyroscope excited by piezo-electric electrodes, mode testing of the cylindrical resonator is difficult. In this paper, a novel vibration testing method for cylindrical resonators is proposed. This method uses a MEMS microphone, which has the characteristics of small size and accurate directivity, to measure the vibration of the cylindrical resonator. A testing system was established, then the system was used to measure the vibration mode of the resonator. The experimental results show that the orientation resolution of the node of the vibration mode is better than 0.1°. This method also has the advantages of low cost and easy operation. It can be used in vibration testing and provide accurate results, which is important for the study of the vibration mode and thermal stability of vibratory cylindrical gyroscopes.

  10. Note: Effect of hot liner in producing {sup 40,48}Ca beam from RIKEN 18-GHz electron cyclotron resonance ion source

    SciTech Connect

    Ozeki, K. Higurashi, Y.; Kidera, M.; Nakagawa, T.

    2015-01-15

    In order to produce a high-intensity and stable {sup 48}Ca beam from the RIKEN 18-GHz electron cyclotron resonance ion source, we have begun testing the production of a calcium beam using a micro-oven. To minimize the consumption rate of the material ({sup 48}Ca), we introduced the “hot liner” method and investigated the effect of the liner on the material consumption rate. The micro-oven was first used to produce the {sup 48}Ca beam for experiments in the RIKEN radioisotope beam factory, and a stable beam could be supplied for a long time with low consumption rate.

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

    SciTech Connect

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

    2015-11-21

    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.

  12. Umbral oscillations as resonant modes of magneto-atmospheric waves. [in sunspots

    NASA Technical Reports Server (NTRS)

    Scheuer, M. A.; Thomas, J. H.

    1981-01-01

    Umbral oscillations in sunspots are identified as a resonant response of the umbral atmosphere to forcing by oscillatory convection in the subphotosphere. The full, linearized equations for magnetoatmospheric waves are solved numerically for a detailed model of the umbral atmosphere, for both forced and free oscillations. Resonant 'fast' modes are found, the lowest mode having a period of 153 s, typical of umbral oscillations. A comparison is made with a similar analysis by Uchida and Sakurai (1975), who calculated resonant modes using an approximate ('quasi-Alfven') form of the wave equations. Whereas both analyses give an appropriate value for the period of oscillation, several new features of the motion follow from the full equations. The resonant modes are due to upward reflection in the subphotosphere (due to increasing sound speed) and downward reflection in the photosphere and low chromosphere (due to increasing Alfven speed); downward reflection at the chromosphere-corona transition is unimportant for these modes.

  13. Onset and Saturation of a Non-resonant Internal Mode in NSTX and Implications For AT Modes in ITER

    SciTech Connect

    J.A. Breslau, M.S. Chance, J. Chen, G.Y. Fu, S,. Gerhardt, N. Gorelenkov, S.C. Jardin and J. Manickam

    2011-08-01

    Motivated by experimental observations of apparently triggerless tearing modes, we have performed linear and nonlinear MHD analysis showing that a non-resonant mode with toroidal mode number n = 1 can develop in the National Spherical Torus eXperiment (NSTX) at moderate normalized βN when the shear is low and the central safety factor q0 is close to but greater than one. This mode, which is related to previously identified ‘infernal’ modes, will saturate and persist, and can develop poloidal mode number m = 2 magnetic islands in agreement with experiments. We have also extended this analysis by performing a free-boundary transport simulation of an entire discharge and showing that, with reasonable assumptions, we can predict the time of mode onset. __________________________________________________

  14. Operation and performance analyses of 350 and 700 MHz low-/high-temperature superconductor nuclear magnetic resonance magnets: A march toward operating frequencies above 1 GHz

    NASA Astrophysics Data System (ADS)

    Hahn, Seungyong; Bascuñán, Juan; Lee, Haigun; Bobrov, Emanuel S.; Kim, Wooseok; Ahn, Min Cheol; Iwasa, Yukikazu

    2009-01-01

    Since 2000, a three-phase program with a final goal to complete a 1 GHz high-resolution low-/high-temperature superconductor (LTS/HTS) nuclear magnetic resonance (NMR) magnet has been conducted at the Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology (MIT). In a LTS/HTS magnet assembly, a HTS insert is placed in the cold bore of a LTS background magnet. To date, two LTS/HTS magnets have been designed, constructed, and tested: a 350 MHz (LH350) in phase 1 and a 700 MHz (LH700) in phase 2. The program's target has recently been upgraded from the original goal of 1 GHz to a new goal of 1.3 GHz. In this paper, we present extensive performance analyses of the two LTS/HTS NMR magnets. Spatial homogeneity and temporal stability of LH350 and LH700, examined with harmonic analysis, and four key issues that became evident in the operation of these two magnets are discussed: (1) field constant reduction, (2) "large" residual Z1 gradient and its temporal decay, (3) large one-periodic tesseral field gradients, and (4) screening-current-induced field in the HTS inserts.

  15. Polarization-independent electromagnetically induced transparency-like transmission in coupled guided-mode resonance structures

    NASA Astrophysics Data System (ADS)

    Lee, Sun-Goo; Kim, Seong-Han; Kim, Kap-Joong; Kee, Chul-Sik

    2017-03-01

    We present two photonic systems that make it possible to realize polarization-independent electromagnetically induced transparency based on guided-mode resonances. Each system is composed of two planar dielectric waveguides and a two-dimensional photonic crystal. Using finite-difference time-domain simulations, we demonstrate that by coupling the two guided-mode resonances with low- and high-quality factors, a narrow transparency window is generated inside a broad background transmission dip produced by the guided-mode resonances. We also show that the time delay that occurs when light beams pass through the proposed systems can be controlled by adjusting the distance between the two waveguides.

  16. Thickness dependent optical mode ferromagnetic resonance in Co/FeNi bilayer

    NASA Astrophysics Data System (ADS)

    Wang, Wenfeng; Chai, Guozhi; Xue, Desheng

    2017-09-01

    We investigate the thickness dependent magnetic properties of an exchange coupled bilayer consisting of Co/FeNi. Inside these bilayers, both acoustic and optical modes of ferromagnetic resonance exist, which are produced by the in-phase and out-of-phase precession of the spins in the different layers. The optical mode ferromagnetic resonance, with a much higher resonance frequency, can be tuned significantly by changing the thickness of the FeNi layer. We show that the thickness dependent optical ferromagnetic resonance frequency is due to the variations of the interlayer exchange coupling with the changes in thickness.

  17. Planar modes free piezoelectric resonators using a phononic crystal with holes.

    PubMed

    Aragón, J L; Quintero-Torres, R; Domínguez-Juárez, J L; Iglesias, E; Ronda, S; Montero de Espinosa, F

    2016-09-01

    By using the principles behind phononic crystals, a periodic array of circular holes made along the polarization thickness direction of piezoceramic resonators are used to stop the planar resonances around the thickness mode band. In this way, a piezoceramic resonator adequate for operation in the thickness mode with an in phase vibration surface is obtained, independently of its lateral shape. Laser vibrometry, electric impedance tests and finite element models are used to corroborate the performances of different resonators made with this procedure. This method can be useful in power ultrasonic devices, physiotherapy and other external medical power ultrasound applications where piston-like vibration in a narrow band is required.

  18. Quantitative Determination of Lateral Mode Dispersion in Film Bulk Acoustic Resonators through Laser Acoustic Imaging

    SciTech Connect

    Ken Telschow; John D. Larson III

    2006-10-01

    Film Bulk Acoustic Resonators are useful for many signal processing applications. Detailed knowledge of their operation properties are needed to optimize their design for specific applications. The finite size of these resonators precludes their use in single acoustic modes; rather, multiple wave modes, such as, lateral wave modes are always excited concurrently. In order to determine the contributions of these modes, we have been using a newly developed full-field laser acoustic imaging approach to directly measure their amplitude and phase throughout the resonator. This paper describes new results comparing modeling of both elastic and piezoelectric effects in the active material with imaging measurement of all excited modes. Fourier transformation of the acoustic amplitude and phase displacement images provides a quantitative determination of excited mode amplitude and wavenumber at any frequency. Images combined at several frequencies form a direct visualization of lateral mode excitation and dispersion for the device under test allowing mode identification and comparison with predicted operational properties. Discussion and analysis are presented for modes near the first longitudinal thickness resonance (~900 MHz) in an AlN thin film resonator. Plate wave modeling, taking account of material crystalline orientation, elastic and piezoelectric properties and overlayer metallic films, will be discussed in relation to direct image measurements.

  19. The resonant, near-resonant, and off-resonant plasmon coupling effects for the bonding modes in two types of asymmetric dimer

    NASA Astrophysics Data System (ADS)

    Li, Quanshui; Hu, Jianling; Wang, Ziya; Wang, Fengping; Bao, Yongjun

    2014-07-01

    The resonant, near-resonant, and off-resonant plasmon coupling effects for the bonding modes in asymmetric dimers are illustrated by two types of configuration, one formed by a gold nanoparticle and a TiO2-Ag core-shell nanoparticle and the other formed by two TiO2-Ag core-shell nanoparticles with suitable sizes. The redshift and blueshift behaviours of the coupled bonding modes with decreasing gap are found under longitudinal and transverse polarization of light for these dimers in the resonant situation, respectively. Under the near-resonant situation, the redshift behaviours of the coupled bonding modes still remain under longitudinal polarization, whereas the two separated modes of monomers after coupling under transverse polarization exhibit no obvious peak-shift behaviours, and the one on the lower frequency side shows an apparent attenuation in the strength. Under the off-resonant situation, the redshift behaviours not only occur in the coupled modes under longitudinal polarization, but also occur in two separated modes under transverse polarization.

  20. Hybrid Alfven resonant mode generation in the magnetosphere-ionosphere coupling system

    SciTech Connect

    Hiraki, Yasutaka; Watanabe, Tomo-Hiko

    2012-10-15

    Feedback unstable Alfven waves involving global field-line oscillations and the ionospheric Alfven resonator (IAR) were comprehensively studied to clarify their properties of frequency dispersion, growth rate, and eigenfunctions. It is discovered that a new mode called here the hybrid Alfven resonant (HAR) mode can be destabilized in the magnetosphere-ionosphere coupling system with a realistic Alfven velocity profile. The HAR mode found in a high frequency range over 0.3 Hz is caused by coupling of IAR modes with strong dispersion and magnetospheric cavity resonances. The harmonic relation of HAR eigenfrequencies is characterized by a constant frequency shift from those of IAR modes. The three modes are robustly found even if effects of two-fluid process and ionospheric collision are taken into account and thus are anticipated to be detected by magnetic field observations in a frequency range of 0.3-1 Hz in auroral and polar-cap regions.

  1. A Dual-Mode Bandpass Filter with Multiple Controllable Transmission-Zeros Using T-Shaped Stub-Loaded Resonators

    PubMed Central

    Yao, Zh.; Wang, C.; Kim, N. Y.

    2014-01-01

    A dual-mode broadband bandpass filter (BPF) with multiple controllable transmission-zeros using T-shaped stub-loaded resonators (TSSLRs) is presented. Due to the symmetrical plane, the odd-even-mode theory can be adopted to characterize the BPF. The proposed filter consists of a dual-mode TSSLR and two modified feed-lines, which introduce two capacitive and inductive source-load (S-L) couplings. Five controllable transmission zeros (TZs) can be achieved for the high selectivity and the wide stopband because of the tunable amount of coupling capacitance and inductance. The center frequency of the proposed BPF is 5.8 GHz, with a 3 dB fraction bandwidth of 8.9%. The measured insertion and return losses are 1.75 and 28.18 dB, respectively. A compact size and second harmonic frequency suppression can be obtained by the proposed BPF with S-L couplings. PMID:24688406

  2. Three-level atom in a three-mode field: The resonant case

    SciTech Connect

    Demidov, D.A.; Solovarov, N.K.

    1995-09-01

    a general expression is obtained for the operator describing evolution of a three-level atom in a three-mode field when the field modes are in resonance with three different transitions in an atomic spectrum. It is shown that, in the absence of one of the modes, the solution obtained coincides with the solution known for a three-level atom in a two-mode field. 7 refs.

  3. Design of 132 GHz gyrotron with 3 GHz tunability for 200 MHz DNP/NMR spectrometer

    NASA Astrophysics Data System (ADS)

    Kumar, Nitin; Singh, Udaybir; Sinha, Ashok Kumar

    2015-01-01

    A complete design of 132 GHz gyrotron for 200 MHz DNP-NMR spectroscopy application is presented in this article. The design is performed considering a frequency tunability range of 3 GHz and output power around 100 W. A smooth frequency tunability is achieved via the excitation of TE03p modes (p = 1-6) through the variation of cavity magnetic field. The start oscillation current calculation is performed to estimate the required magnetic field for each TE03p mode. Cold cavity analysis and beam-wave interaction computation are carried out for the estimation of quality factor, resonant frequency corresponding to each TE03p mode, axial electric field profile and output power. Other important components of gyrotron such as magnetron injection gun, non-linear taper and RF window are also designed considering the smooth frequency tunability a main design parameter.

  4. Wireless actuation of bulk acoustic modes in micromechanical resonators

    NASA Astrophysics Data System (ADS)

    Mateen, Farrukh; Brown, Benjamin; Erramilli, Shyamsunder; Mohanty, Pritiraj

    2016-08-01

    We report wireless actuation of a Lamb wave micromechanical resonator from a distance of over 1 m with an efficiency of over 15%. Wireless actuation of conventional micromechanical resonators can have broad impact in a number of applications from wireless communication and implantable biomedical devices to distributed sensor networks.

  5. Fundamental mode rectangular waveguide system for electron-cyclotron resonant heating (ECRH) for tandem mirror experiment-upgrade (TMX-U)

    SciTech Connect

    Rubert, R.R.; Felker, B.; Stallard, B.W.; Williams, C.W.

    1983-12-01

    We present a brief history of TMX-U's electron cyclotron resonant heating (ECRH) progress. We emphasize the 2-year performance of the system, which is composed of four 200-kW pulsed gyrotrons operated at 28 GHz. This system uses WR42 waveguide inside the vacuum vessel, and includes barrier windows, twists, elbows, and antennas, as well as custom-formed waveguides. Outside the TMX-U vessel are directional couplers, detectors, elbows, and waveguide bends in WR42 rectangular waveguide. An arc detector, mode filter, eight-arm mode converter, and water load in the 2.5-in. circular waveguide are attached directly to the gyrotron. Other specific areas discussed include the operational performance of the TMX-U pulsed gyrotrons, windows and component arcing, alignment, mode generation, and extreme temperature variations. Solutions for a number of these problems are described.

  6. High-sensitivity imaging with lateral resonance mode atomic force microscopy.

    PubMed

    Ding, Ren-Feng; Yang, Chih-Wen; Huang, Kuang-Yuh; Hwang, Ing-Shouh

    2016-11-03

    In the operation of a dynamic mode atomic force microscope, a micro-fabricated rectangular cantilever is typically oscillated at or near its mechanical resonance frequency. Lateral bending resonances of cantilevers are rarely used because the resonances are not expected to be detected by the beam-deflection method. In this work, we found that micro-cantilevers with a large tip produced an out-of-plane displacement in lateral resonance (LR), which could be detected with the beam-deflection method. Finite-element analysis indicated that the presence of a large tip is the major source of the out-of-plane coupling for the LR. We also imaged a heterogeneous sample by operating a cantilever in LR, torsional resonance, and tapping modes. LR mode yielded a small deformation and noise level in the height maps as well as a high contrast and small noise level in the phase maps. LR mode also had a resonance frequency that was orders of magnitude higher than that of tapping mode. Operation with LR mode may have the benefits of high-speed scanning, high-sensitivity imaging, and mapping of in-plane mechanical properties of the sample surface. In general, LR mode may become a powerful new atomic force microscopy technique for characterizing sample materials.

  7. Equivalent-circuit model for the thickness-shear mode resonator with a viscoelastic film near film resonance.

    PubMed

    Martin, S J; Bandey, H L; Cernosek, R W; Hillman, A R; Brown, M J

    2000-01-01

    We derive a lumped-element, equivalent-circuit model for the thickness-shear mode (TSM) resonator with a viscoelastic film. This modified Butterworth-Van Dyke model includes in the motional branch a series LCR resonator, representing the quartz resonance, and a parallel LCR resonator, representing the film resonance. This model is valid in the vicinity of film resonance, which occurs when the acoustic phase shift across the film is an odd multiple of pi/2 rad. For low-loss films, this model accurately predicts the frequency changes and damping that arise at resonance and is a reasonable approximation away from resonance. Elements of the parallel LCR resonator are explicitly related to film properties and can be interpreted in terms of elastic energy storage and viscous power dissipation. The model leads to a simple graphical interpretation of the coupling between the quartz and film resonances and facilitates understanding of the resulting responses. These responses are compared with predictions from the transmission-line and Sauerbrey models.

  8. Two-frequency heating technique at the 18 GHz electron cyclotron resonance ion source of the National Institute of Radiological Sciences

    SciTech Connect

    Biri, S.; Rácz, R.; Sasaki, N.; Takasugi, W.

    2014-02-15

    The two-frequency heating technique was studied to increase the beam intensities of highly charged ions provided by the high-voltage extraction configuration (HEC) ion source at the National Institute of Radiological Sciences (NIRS). The observed dependences on microwave power and frequency suggested that this technique improved plasma stability but it required precise frequency tuning and more microwave power than was available before 2013. Recently, a new, high-power (1200 W) wide band-width (17.1–18.5 GHz) travelling-wave-tube amplifier (TWTA) was installed. After some single tests with klystron and TWT amplifiers the simultaneous injection of the two microwaves has been successfully realized. The dependence of highly charged ions (HCI) currents on the superposed microwave power was studied by changing only the output power of one of the two amplifiers, alternatively. While operating the klystron on its fixed 18.0 GHz, the frequency of the TWTA was swept within its full limits (17.1–18.5 GHz), and the effect of this frequency on the HCI-production rate was examined under several operation conditions. As an overall result, new beam records of highly charged argon, krypton, and xenon beams were obtained at the NIRS-HEC ion source by this high-power two-frequency operation mode.

  9. Two-frequency heating technique at the 18 GHz electron cyclotron resonance ion source of the National Institute of Radiological Sciences

    NASA Astrophysics Data System (ADS)

    Biri, S.; Kitagawa, A.; Muramatsu, M.; Drentje, A. G.; Rácz, R.; Yano, K.; Kato, Y.; Sasaki, N.; Takasugi, W.

    2014-02-01

    The two-frequency heating technique was studied to increase the beam intensities of highly charged ions provided by the high-voltage extraction configuration (HEC) ion source at the National Institute of Radiological Sciences (NIRS). The observed dependences on microwave power and frequency suggested that this technique improved plasma stability but it required precise frequency tuning and more microwave power than was available before 2013. Recently, a new, high-power (1200 W) wide band-width (17.1-18.5 GHz) travelling-wave-tube amplifier (TWTA) was installed. After some single tests with klystron and TWT amplifiers the simultaneous injection of the two microwaves has been successfully realized. The dependence of highly charged ions (HCI) currents on the superposed microwave power was studied by changing only the output power of one of the two amplifiers, alternatively. While operating the klystron on its fixed 18.0 GHz, the frequency of the TWTA was swept within its full limits (17.1-18.5 GHz), and the effect of this frequency on the HCI-production rate was examined under several operation conditions. As an overall result, new beam records of highly charged argon, krypton, and xenon beams were obtained at the NIRS-HEC ion source by this high-power two-frequency operation mode.

  10. Tearing mode suppression by using resonant magnetic perturbation coils on J-TEXT tokamak

    NASA Astrophysics Data System (ADS)

    J-TEXT Team; Rao, B.; Ding, Y. H.; Hu, Q. M.; Shi, W. F.; Zhang, X. Q.; Zhang, M.; Jin, X. S.; Nan, J. Y.; Yu, K. X.; Zhuang, G.

    2013-01-01

    A series of experiments on the interactions between external resonant magnetic perturbations (RMP) and plasmas has recently been conducted, using static resonant magnetic perturbation (SRMP) coils on the Joint Texas Experimental Tokamak (J-TEXT). The tearing mode can be completely suppressed by applying SRMP. However, the locked mode is likely to be stimulated under a larger SRMP field even though the tearing mode has been first suppressed. A numerical simulation shows three typical regimes of RMP's effects on the tearing mode, which are consistent with experimental results.

  11. Piezoelectric transduction of flexural modes in pre-stressed microbeam resonators

    NASA Astrophysics Data System (ADS)

    Torri, G. B.; Janssen, N. M. A.; Zeng, Z.; Rottenberg, X.; Karabacak, D. M.; Vandecasteele, M.; Van Hoof, C.; Puers, R.; Tilmans, H. A. C.

    2014-08-01

    This paper reports on the optimization of the design of piezoelectric transducer elements integrated on doubly-clamped microbeam resonators utilized as (bio)chemical sensors. We report and emphasize the often forgotten influence of membrane stresses on defining the dimensions and optimal position of the piezoelectric transducer elements. The study takes into account stress induced structural changes and provides models for the equivalent motional parameters of resonators with particular shapes of the transducers matching the flexural modes of vibration. The above is analyzed theoretically using numerical models and is confirmed by impedance measurements and optical measurements of fabricated doubly-clamped beam resonators. We propose various transducer designs and highlight the advantages of using higher order vibration modes by implementing specially designed mode matching transducer elements. It is concluded that the paper describes and highlights the importance of accounting for the membrane stresses to optimize the resonator performance and the low power in electronic feedback of resonating sensing systems.

  12. Exploring the distinction between experimental resonant modes and theoretical eigenmodes: From vibrating plates to laser cavities

    NASA Astrophysics Data System (ADS)

    Tuan, P. H.; Wen, C. P.; Yu, Y. T.; Liang, H. C.; Huang, K. F.; Chen, Y. F.

    2014-02-01

    Experimentally resonant modes are commonly presumed to correspond to eigenmodes in the same bounded domain. However, the one-to-one correspondence between theoretical eigenmodes and experimental observations is never reached. Theoretically, eigenmodes in numerous classical and quantum systems are the solutions of the homogeneous Helmholtz equation, whereas resonant modes should be solved from the inhomogeneous Helmholtz equation. In the present paper we employ the eigenmode expansion method to derive the wave functions for manifesting the distinction between eigenmodes and resonant modes. The derived wave functions are successfully used to reconstruct a variety of experimental results including Chladni figures generated from the vibrating plate, resonant patterns excited from microwave cavities, and lasing modes emitted from the vertical cavity.

  13. Exploring the distinction between experimental resonant modes and theoretical eigenmodes: from vibrating plates to laser cavities.

    PubMed

    Tuan, P H; Wen, C P; Yu, Y T; Liang, H C; Huang, K F; Chen, Y F

    2014-02-01

    Experimentally resonant modes are commonly presumed to correspond to eigenmodes in the same bounded domain. However, the one-to-one correspondence between theoretical eigenmodes and experimental observations is never reached. Theoretically, eigenmodes in numerous classical and quantum systems are the solutions of the homogeneous Helmholtz equation, whereas resonant modes should be solved from the inhomogeneous Helmholtz equation. In the present paper we employ the eigenmode expansion method to derive the wave functions for manifesting the distinction between eigenmodes and resonant modes. The derived wave functions are successfully used to reconstruct a variety of experimental results including Chladni figures generated from the vibrating plate, resonant patterns excited from microwave cavities, and lasing modes emitted from the vertical cavity.

  14. Direct electrical-to-optical conversion and light modulation in micro whispering-gallery-mode resonators

    NASA Technical Reports Server (NTRS)

    Maleki, Lute (Inventor); Levi, Anthony F. J. (Inventor)

    2005-01-01

    Techniques for directly converting an electrical signal into an optical signal by using a whispering gallery mode optical resonator formed of a dielectric material that allows for direct modulation of optical absorption by the electrical signal.

  15. Transition of lasing modes in polymeric opal photonic crystal resonating cavity.

    PubMed

    Shi, Lan-Ting; Zheng, Mei-Ling; Jin, Feng; Dong, Xian-Zi; Chen, Wei-Qiang; Zhao, Zhen-Sheng; Duan, Xuan-Ming

    2016-06-10

    We demonstrate the transition of lasing modes in the resonating cavity constructed by polystyrene opal photonic crystals and 7 wt. % tert-butyl Rhodamine B doped polymer film. Both single mode and multiple mode lasing emission are observed from the resonating cavity. The lasing threshold is determined to be 0.81  μJ/pulse for single mode lasing emission and 2.25  μJ/pulse for multiple mode lasing emission. The single mode lasing emission is attributed to photonic lasing resulting from the photonic bandgap effect of the opal photonic crystals, while the multiple mode lasing emission is assigned to random lasing due to the defects in the photonic crystals. The result would benefit the development of low threshold polymeric solid state photonic crystal lasers.

  16. Efficient frequency generation in phoXonic cavities based on hollow whispering gallery mode resonators

    PubMed Central

    Farnesi, Daniele; Righini, Giancarlo; Nunzi Conti, Gualtiero; Soria, Silvia

    2017-01-01

    We report on nonlinear optical effects on phoxonic cavities based on hollow whispering gallery mode resonators pumped with a continuous wave laser. We observed stimulated scattering effects such as Brillouin and Raman, Kerr effects such as degenerated and non-degenerated four wave mixing, and dispersive wave generation. These effects happened concomitantly. Hollow resonators give rise to a very rich nonlinear scenario due to the coexistence of several family modes. PMID:28266641

  17. White-Light Whispering Gallery Mode Optical Resonator System and Method

    NASA Technical Reports Server (NTRS)

    Matsko, Andrey B. (Inventor); Savchenkov, Anatoliy A. (Inventor); Maleki, Lute (Inventor)

    2009-01-01

    An optical resonator system and method that includes a whispering-gallery mode (WGM) optical resonator that is capable of resonating across a broad, continuous swath of frequencies is provided. The optical resonator of the system is shaped to support at least one whispering gallery mode and includes a top surface, a bottom surface, a side wall, and a first curved transition region extending between the side wall and the top surface. The system further includes a coupler having a coupling surface which is arranged to face the transition region of the optical resonator and in the vicinity thereof such that an evanescent field emitted from the coupler is capable of being coupled into the optical resonator through the first curved transition region

  18. Theoretical study of transverse mode selection in laser resonator with volume Bragg gratings

    NASA Astrophysics Data System (ADS)

    Hu, Jing; Gao, Fan; Zhang, Xiang; Yuan, Xiao

    2016-11-01

    Volume Bragg grating (VBG) can be used in laser resonator to control the transverse distribution due to its excellent Bragg selectivity. The coupled-wave theory is used to analyze the angular selectivity of VBG, and the output modes of the volume Bragg resonator are simulated with the fast Fourier transform (FFT) method and the coupled-wave theory. In this paper, the volume Bragg grating is inserted into a plane-parallel resonator, the intensity distribution and diffraction losses for the mode of TEM00, TEM10 and TEM20 are simulated, and the loss difference for different modes at different angular selectivity of VBGs are discussed. At the VBG angular selectivity of 3 mrad, the diffraction loss for fundamental mode is of 6.3%, while the diffraction loss for TEM10 and TEM20 mode are 19.8% and 32.7%, respectively. Therefore, TEM10 and TEM20 can be easily suppressed if the gain is between 6.3% and 19.8%, and a fundamental transverse mode can be obtained. Besides, the simulation results show that the intensity distribution profile of the transverse modes become smooth with the insertion of VBG, but the diffraction losses of transverse modes are increasing, and the diffraction loss increases with the order number of transverse modes increasing. Moreover, the loss difference between modes is getting large under the effect of VBG. The high loss difference between different modes is good for transverse mode selection, and VBG with reasonable angular selectivity in laser resonator will force the multi-mode to operate in a single transverse mode, which may has potential applications in lasers.

  19. Performance of hole coupling resonator in the presence of asymmetric modes and FEL gain

    SciTech Connect

    Xie, Ming; Kim, Kwang-Je.

    1991-08-01

    We continue the study of the hole coupling resonator for free electron laser (FEL) application. The previous resonator code is further developed to include the effects of the azimutally asymmetric modes and the FEL gain. The implication of the additional higher order modes is that there are more degeneracies to be avoided in tuning the FEL wavelengths. The FEL interaction is modeled by constructing a transfer map in the small signal regime and incorporating it into the resonator code. The FEL gain is found to be very effective in selecting a dominant mode from the azimuthally symmetric class of modes. Schemes for broad wavelength tuning based on passive mode control via adjustable apertures are discussed. 12 refs., 7 figs., 1 tab.

  20. Study of node and mass sensitivity of resonant mode based cantilevers with concentrated mass loading

    SciTech Connect

    Zhang, Kewei Chai, Yuesheng; Fu, Jiahui

    2015-12-15

    Resonant-mode based cantilevers are an important type of acoustic wave based mass-sensing devices. In this work, the governing vibration equation of a bi-layer resonant-mode based cantilever attached with concentrated mass is established by using a modal analysis method. The effects of resonance modes and mass loading conditions on nodes and mass sensitivity of the cantilever were theoretically studied. The results suggested that the node did not shift when concentrated mass was loaded on a specific position. Mass sensitivity of the cantilever was linearly proportional to the square of the point displacement at the mass loading position for all the resonance modes. For the first resonance mode, when mass loading position x{sub c} satisfied 0 < x{sub c} < ∼ 0.3l (l is the cantilever beam length and 0 represents the rigid end), mass sensitivity decreased as the mass increasing while the opposite trend was obtained when mass loading satisfied ∼0.3l ≤ x{sub c} ≤ l. Mass sensitivity did not change when concentrated mass was loaded at the rigid end. This work can provide scientific guidance to optimize the mass sensitivity of a resonant-mode based cantilever.

  1. Higher-order vibrational mode frequency tuning utilizing fishbone-shaped microelectromechanical systems resonator

    NASA Astrophysics Data System (ADS)

    Suzuki, Naoya; Tanigawa, Hiroshi; Suzuki, Kenichiro

    2013-04-01

    Resonators based on microelectromechanical systems (MEMS) have received considerable attention for their applications for wireless equipment. The requirements for this application include small size, high frequency, wide bandwidth and high portability. However, few MEMS resonators with wide-frequency tuning have been reported. A fishbone-shaped resonator has a resonant frequency with a maximum response that can be changed according to the location and number of several exciting electrodes. Therefore, it can be expected to provide wide-frequency tuning. The resonator has three types of electrostatic forces that can be generated to deform a main beam. We evaluate the vibrational modes caused by each exciting electrodes by comparing simulated results with measured ones. We then successfully demonstrate the frequency tuning of the first to fifth resonant modes by using the algorithm we propose here. The resulting frequency tuning covers 178 to 1746 kHz. In addition, we investigate the suppression of the anchor loss to enhance the Q-factor. An experiment shows that tapered-shaped anchors provide a higher Q-factor than rectangular-shaped anchors. The Q-factor of the resonators supported by suspension beams is also discussed. Because the suspension beams cause complicated vibrational modes for higher frequencies, the enhancement of the Q-factor for high vibrational modes cannot be obtained here. At present, the tapered-anchor resonators are thought to be most suitable for frequency tuning applications.

  2. Linear and nonlinear behavior of crystalline optical whispering gallery mode resonators

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy A.; Matsko, Andrey B.; Ilchenko, Vladimir S.; Maleki, Lute

    2004-01-01

    We demonstrate strong nonlinear behavior of high-Q whispering gallery mode (WGM) resonators made out of various crystals adn devices based on the resonators. The maximum WGM optical Q-fact or achieved at room temperature exceeds 2X10 to the tenth power.

  3. High-Q lattice mode matched structural resonances in terahertz metasurfaces

    SciTech Connect

    Xu, Ningning; Zhang, Weili; Singh, Ranjan

    2016-07-11

    The quality (Q) factor of metamaterial resonances is limited by the radiative and non-radiative losses. At terahertz frequencies, the dominant loss channel is radiative in nature since the non-radiative losses are low due to high conductivity of metals. Radiative losses could be suppressed by engineering the meta-atom structure. However, such suppression usually occurs at the fundamental resonance mode which is typically a closed mode resonance such as an inductive-capacitive resonance or a Fano resonance. Here, we report an order of magnitude enhancement in Q factor of all the structural eigenresonances of a split-ring resonator fueled by the lattice mode matching. We match the fundamental order diffractive mode to each of the odd and even eigenresonances, thus leading to a tremendous line-narrowing of all the resonances. Such precise tailoring and control of the structural resonances in a metasurface lattice could have potential applications in low-loss devices, sensing, and design of high-Q metamaterial cavities.

  4. Effects of locally resonant modes on underwater sound absorption in viscoelastic materials.

    PubMed

    Wen, Jihong; Zhao, Honggang; Lv, Linmei; Yuan, Bo; Wang, Gang; Wen, Xisen

    2011-09-01

    Recently, by introducing locally resonant scatterers with spherical shape proposed in phononic crystals into design of underwater sound absorption materials, the low-frequency underwater sound absorption phenomenon induced by the localized resonances is observed. To reveal this absorption mechanism, the effect of the locally resonant mode on underwater sound absorption should be studied. In this paper, the finite element method, which is testified efficiently by comparing the calculation results with those of the layer multiple scattering method, is introduced to investigate the dynamic modes and the corresponding sound absorption of localized resonance. The relationship between the resonance modes described with the displacement contours of one unit cell and the corresponding absorption spectra is discussed in detail, which shows that the localized resonance leads to the absorption peak, and the mode conversion from longitudinal to transverse waves at the second absorption peak is more efficient than that at the first one. Finally, to show the modeling capability of FEM and investigate shape effects of locally resonant scatterers on underwater sound absorption, the absorption properties of viscoelastic materials containing locally resonant scatterers with ellipsoidal shape are discussed.

  5. Spatial-dependent resonance mode and frequency of rotationally periodic structures subjected to standing wave excitation

    NASA Astrophysics Data System (ADS)

    Zhang, Dongsheng; Wang, Shiyu

    2017-09-01

    This work examines the distinct resonance vibration of rotationally periodic structures. An analytical model of a sample stepped-plate structure subjected to standing wave excitation is developed by elasticity theory. Spatial-dependent resonance mode and resonance frequency are formulated by perturbation-superposition method. Different from the natural mode and natural frequency, a sinusoidal fluctuation of the resonance frequency is identified between the two split natural frequencies for single standing wave excitation. The resonance mode does not have preferred orientation because it is determined by excitation orientation. The resonance behaviors are different from those near the repeated natural frequencies. The response to a standing wave pair is also calculated and compared with that to the mathematically equivalent traveling wave, where significant difference is identified. The results indicate that purer traveling wave can be created by using a standing wave pair with pre-selected spatial phase and excitation frequency. Reverse traveling direction can be realized by altering excitation frequency. A test rig is designed and fabricated for verification purpose. The experiment validates that the response near the split natural frequencies is in phase with the external standing wave excitation. The resonance frequency varies with the excitation orientation for the split natural frequencies but it remains constant for the repeated natural frequencies. Potential applications of the spatial-dependent resonance mode and frequency are presented.

  6. Guided mode resonance in subwavelength metallodielectric free-standing grating for bandpass filtering.

    PubMed

    Sakat, Emilie; Vincent, Grégory; Ghenuche, Petru; Bardou, Nathalie; Collin, Stéphane; Pardo, Fabrice; Pelouard, Jean-Luc; Haïdar, Riad

    2011-08-15

    We present the experimental study of a free-standing metallic guided-mode resonant structure, for bandpass filtering applications in the mid-IR wavelength range. Structure consists of a subwavelength gold grating with narrow slits deposited on a silicon nitride membrane. High optical transmission is measured with up to 78% transmission at resonance. Angularly resolved spectra are presented revealing Fano-type resonance. © 2011 Optical Society of America

  7. Resonant mode characterisation of a cylindrical Helmholtz cavity excited by a shear layer.

    PubMed

    Bennett, Gareth J; Stephens, David B; Rodriguez Verdugo, Francisco

    2017-01-01

    This paper investigates the interaction between the shear-layer over a circular cavity with a relatively small opening and the flow-excited acoustic response of the volume within to shear-layer instability modes. Within the fluid-resonant category of cavity oscillation, most research has been conducted on rectangular geometries: generally restricted to longitudinal standing waves, or when cylindrical: to Helmholtz resonance. In practical situations, however, where the cavity is subject to a range of flow speeds, many different resonant mode types may be excited. The current work presents a cylindrical cavity design where Helmholtz oscillation, longitudinal resonance, and azimuthal acoustic modes may all be excited upon varying the flow speed. Experiments performed show how lock-on between each of the three fluid-resonances and shear-layer instability modes can be generated. A circumferential array of microphones flush-mounted with the internal surface of the cavity wall was used to decompose the acoustic pressure field into acoustic modes and has verified the excitation of higher order azimuthal modes by the shear-layer. For azimuthal modes especially, the location of the cavity opening affects the pressure response. A numerical solution is validated and provides additional insight and will be applied to more complex aeronautical and automotive geometries in the future.

  8. Influence of microwave driver coupling design on plasma density at Testbench for Ion sources Plasma Studies, a 2.45 GHz Electron Cyclotron Resonance Plasma Reactor

    NASA Astrophysics Data System (ADS)

    Megía-Macías, A.; Cortázar, O. D.; Vizcaíno-de-Julián, A.

    2014-03-01

    A comparative study of two microwave driver systems (preliminary and optimized) for a 2.45 GHz hydrogen Electron Cyclotron Resonance plasma generator has been conducted. The influence on plasma behavior and parameters of stationary electric field distribution in vacuum, i.e., just before breakdown, along all the microwave excitation system is analyzed. 3D simulations of resonant stationary electric field distributions, 2D simulations of external magnetic field mapping, experimental measurements of incoming and reflected power, and electron temperature and density along the plasma chamber axis have been carried out. By using these tools, an optimized set of plasma chamber and microwave coupler has been designed paying special attention to the optimization of stationary electric field value in the center of the plasma chamber. This system shows a strong stability on plasma behavior allowing a wider range of operational parameters and even sustaining low density plasma formation without external magnetic field. In addition, the optimized system shows the capability to produce values of plasma density four times higher than the preliminary as a consequence of a deeper penetration of the magnetic resonance surface in relative high electric field zone by keeping plasma stability. The increment of the amount of resonance surface embedded in the plasma under high electric field is suggested as a key factor.

  9. Patterned FeNi soft magnetic strips film with tunable resonance frequency from 1 to 10.6 GHz

    PubMed Central

    Ren, Yong; Li, Xinxi; Wang, Yan; Ren, Jiankun; Zhang, Yan; Dai, Bo; Yan, Haiyang; Sun, Guangai; Peng, Shuming

    2016-01-01

    Soft magnetic films with a wide-range tunable ferromagnetic resonance frequency are suitable for miniaturization and multifunctionalization of microwave integrated circuits. Fabrication of these films for high-frequency applications is usually complicated and difficult. We demonstrate a simple method to fabricate patterned FeNi soft magnetic strip films by magnetron sputtering and photolithography. Films prepared by this method exhibits a tunable in-plane uniaxial magnetic anisotropy (IPUMA) for different strip widths and gaps. As the strip widths changing from 500 to 2 μm, the IPUMA field increases monotonically from 2.2 to 576 Oe and resonance frequency from 1 to 10.6 GHz(which covers four microwave bands, including the L,S,C and X bands) respectively. This ultra-wide-range adjustability of resonance frequency can be attributed to shape anisotropy of strips. Considering that FeNi alloy has relatively low magnetocrystalline anisotropy, so a wider adjustable range of resonance frequency could be obtained using materials with stronger magnetocrystalline anisotropy. PMID:27561328

  10. Patterned FeNi soft magnetic strips film with tunable resonance frequency from 1 to 10.6 GHz

    NASA Astrophysics Data System (ADS)

    Ren, Yong; Li, Xinxi; Wang, Yan; Ren, Jiankun; Zhang, Yan; Dai, Bo; Yan, Haiyang; Sun, Guangai; Peng, Shuming

    2016-08-01

    Soft magnetic films with a wide-range tunable ferromagnetic resonance frequency are suitable for miniaturization and multifunctionalization of microwave integrated circuits. Fabrication of these films for high-frequency applications is usually complicated and difficult. We demonstrate a simple method to fabricate patterned FeNi soft magnetic strip films by magnetron sputtering and photolithography. Films prepared by this method exhibits a tunable in-plane uniaxial magnetic anisotropy (IPUMA) for different strip widths and gaps. As the strip widths changing from 500 to 2 μm, the IPUMA field increases monotonically from 2.2 to 576 Oe and resonance frequency from 1 to 10.6 GHz(which covers four microwave bands, including the L,S,C and X bands) respectively. This ultra-wide-range adjustability of resonance frequency can be attributed to shape anisotropy of strips. Considering that FeNi alloy has relatively low magnetocrystalline anisotropy, so a wider adjustable range of resonance frequency could be obtained using materials with stronger magnetocrystalline anisotropy.

  11. Influence of microwave driver coupling design on plasma density at Testbench for Ion sources Plasma Studies, a 2.45 GHz electron cyclotron resonance plasma reactor.

    PubMed

    Megía-Macías, A; Cortázar, O D; Vizcaíno-de-Julián, A

    2014-03-01

    A comparative study of two microwave driver systems (preliminary and optimized) for a 2.45 GHz hydrogen Electron Cyclotron Resonance plasma generator has been conducted. The influence on plasma behavior and parameters of stationary electric field distribution in vacuum, i.e., just before breakdown, along all the microwave excitation system is analyzed. 3D simulations of resonant stationary electric field distributions, 2D simulations of external magnetic field mapping, experimental measurements of incoming and reflected power, and electron temperature and density along the plasma chamber axis have been carried out. By using these tools, an optimized set of plasma chamber and microwave coupler has been designed paying special attention to the optimization of stationary electric field value in the center of the plasma chamber. This system shows a strong stability on plasma behavior allowing a wider range of operational parameters and even sustaining low density plasma formation without external magnetic field. In addition, the optimized system shows the capability to produce values of plasma density four times higher than the preliminary as a consequence of a deeper penetration of the magnetic resonance surface in relative high electric field zone by keeping plasma stability. The increment of the amount of resonance surface embedded in the plasma under high electric field is suggested as a key factor.

  12. Design of low-cost resonant mode sensors

    NASA Astrophysics Data System (ADS)

    Kazinczi, Robert; Turmezei, P.; Mollinger, Jeff R.; Bossche, Andre

    2001-11-01

    This study introduces a novel design for low-cost MEMS devices, which exploit the benefits of resonant operation and maintain stable performance. Resonant devices provide high sensitivity and convenient signal processing. The drawback of the method is the sensitivity to undesired environmental effects and aging. The environment induced degradation processes and the long-term stability of thin film resonators were investigated previously. The two major reliability problems were stiffening effect and degrading shock response, both affecting the mechanical resonance frequency. Based on these results, new, low-cost pressure sensors and accelerometers were designed and fabricated. The structures are based on locally reinforced silicon nitride membranes, and double-clamped 3-D silicon nitride bridges as sensing elements. This double mechanical structure allows separate optimization of the membrane and the bridges for the workload and for the most efficient driving and sensing. The 3-D bridges work as mechanical amplifiers, resulting in higher detection efficiency. The reliability tests indicated, that a low-cost atmospheric packaging is efficient, thus the bridges do not require vacuum encapsulation with multiple-wafer process. External mechanical and thermal excitation combined with piezoresistive and optical detection methods are implemented in the different sensors. Differential detection using reference resonators allow compensation for thermal, environment- and aging-induced stresses.

  13. Inter-spin distance determination using L-band (1-2 GHz) non-adiabatic rapid sweep electron paramagnetic resonance (NARS EPR)

    NASA Astrophysics Data System (ADS)

    Kittell, Aaron W.; Hustedt, Eric J.; Hyde, James S.

    2012-08-01

    Site-directed spin-labeling electron paramagnetic resonance (SDSL EPR) provides insight into the local structure and motion of a spin probe strategically attached to a molecule. When a second spin is introduced to the system, macromolecular information can be obtained through measurement of inter-spin distances either by continuous wave (CW) or pulsed electron double resonance (ELDOR) techniques. If both methodologies are considered, inter-spin distances of 8-80 Å can be experimentally determined. However, there exists a region at the upper limit of the conventional X-band (9.5 GHz) CW technique and the lower limit of the four-pulse double electron-electron resonance (DEER) experiment where neither method is particularly reliable. The work presented here utilizes L-band (1.9 GHz) in combination with non-adiabatic rapid sweep (NARS) EPR to address this opportunity by increasing the upper limit of the CW technique. Because L-band linewidths are three to seven times narrower than those at X-band, dipolar broadenings that are small relative to the X-band inhomogeneous linewidth become observable, but the signal loss, due to the frequency dependence of the Boltzmann factor, has made L-band especially challenging. NARS has been shown to increase sensitivity by a factor of five, and overcomes much of this loss, making L-band distance determination more feasible [1]. Two different systems are presented, and distances of 18-30 Å have been experimentally determined at physiologically relevant temperatures. Measurements are in excellent agreement with a helical model and values determined by DEER.

  14. Inter-spin distance determination using L-band (1-2 GHz) non-adiabatic rapid sweep electron paramagnetic resonance (NARS EPR)

    PubMed Central

    Kittell, Aaron W.; Hustedt, Eric J.; Hyde, James S.

    2014-01-01

    Site-directed spin-labeling electron paramagnetic resonance (SDSL EPR) provides insight into the local structure and motion of a spin probe strategically attached to a molecule. When a second spin is introduced to the system, macromolecular information can be obtained through measurement of inter-spin distances either by continuous wave (CW) or pulsed electron double resonance (ELDOR) techniques. If both methodologies are considered, inter-spin distances of 8 to 80 Å can be experimentally determined. However, there exists a region at the upper limit of the conventional X-band (9.5 GHz) CW technique and the lower limit of the four-pulse double electron-electron resonance (DEER) experiment where neither method is particularly reliable. The work presented here utilizes L-band (1.9 GHz) in combination with non-adiabatic rapid sweep (NARS) EPR to address this opportunity by increasing the upper limit of the CW technique. Because L-band linewidths are three to seven times narrower than those at X-band, dipolar broadenings that are small relative to the X-band inhomogeneous linewidth become observable, but the signal loss due to the frequency dependence of the Boltzmann factor, has made L-band especially challenging. NARS has been shown to increase sensitivity by a factor of five, and overcomes much of this loss, making L-band distance determination more feasible [1]. Two different systems are presented and distances of 18–30 Å have been experimentally determined at physiologically relevant temperatures. Measurements are in excellent agreement with a helical model and values determined by DEER. PMID:22750251

  15. Changes of shape of the whispering gallery modes resonators due to their movement in inertial space

    NASA Astrophysics Data System (ADS)

    Filatov, Yuri V.; Kukaev, Alexander S.; Shalymov, Egor V.; Venediktov, Vladimir Yu.

    2016-11-01

    Influence of the centrifugal forces on angular velocity sensors that measure a spectral shift of whispering gallery modes is investigated. Spherical whispering gallery mode resonators of different materials are considered as sensing elements. The study is based on the results of the simulation in OOFELIE::Multiphysics software.

  16. Topography-coupled resonance between Mars normal-modes and the tidal force of the Phobos

    NASA Astrophysics Data System (ADS)

    Tian, Y.; Zheng, Y.

    2016-12-01

    Phobos is the largest moon of Mars. The gravity attraction of Phobos to Mars is a periodic force, which may excite seismic waves inside Mars. Since Phobos is below the synchronous orbit, its orbit is continuously decreasing due to the tidal effect. This will result in a monotonic increase in its orbital frequency, which may eventually intrude into the seismic normal-mode frequency range to cause resonance. The objective of this research is to investigate whether such a resonance phenomenon can occur and what the consequence is. As we know, resonance happens when the periodic tidal force has a similar frequency as that of martian normal modes. It can be shown that such a resonance will not occur if Mars is perfectly spherical because the tidal force can only excite modes of the same angular order. For the same angular order, the tidal force frequencies are always smaller than those of the normal modes. However, when we consider the effect of topography of Mars, the resonance can occur because of coupling of normal modes. We use numerical method to calculate when the resonance will occur. We firstly solve for the normal modes of Mars by idealizing it as a solid elastic sphere. At the second step, we calculate the excitation effect of gravitational force from Phobos on each individual normal mode. For example, the gravity tidal force F at L=5, m=5 F55 can excite a normal mode 0S5 which can be coupled to 0T2. The third step is to calculate the frequency that the resonance will happen. For example, when the rotation frequency of Phobos increase to 0.8 mRad/s, the tidal force at L=5, m=5 can reach 4mRad/s which is the eigen-frequency of 0T2. Since we have calculated the coupling factors between each individual mode, the amplitude coefficients can be solved by a linear equation. We can observe a 100 times of amplitude increase of mode 0T2, which convince us the resonance will happen. The resonance may cause large amplitude of ground vibration of Mars. From our calculation

  17. Photoelectron emission from metal surfaces induced by radiation emitted by a 14 GHz electron cyclotron resonance ion source

    NASA Astrophysics Data System (ADS)

    Laulainen, Janne; Kalvas, Taneli; Koivisto, Hannu; Komppula, Jani; Kronholm, Risto; Tarvainen, Olli

    2016-02-01

    Photoelectron emission measurements have been performed using a room-temperature 14 GHz ECR ion source. It is shown that the photoelectron emission from Al, Cu, and stainless steel (SAE 304) surfaces, which are common plasma chamber materials, is predominantly caused by radiation emitted from plasma with energies between 8 eV and 1 keV. Characteristic X-ray emission and bremsstrahlung from plasma have a negligible contribution to the photoelectron emission. It is estimated from the measured data that the maximum conceivable photoelectron flux from plasma chamber walls is on the order of 10% of the estimated total electron losses from the plasma.

  18. Photoelectron emission from metal surfaces induced by radiation emitted by a 14 GHz electron cyclotron resonance ion source

    SciTech Connect

    Laulainen, Janne Kalvas, Taneli; Koivisto, Hannu; Komppula, Jani; Kronholm, Risto; Tarvainen, Olli

    2016-02-15

    Photoelectron emission measurements have been performed using a room-temperature 14 GHz ECR ion source. It is shown that the photoelectron emission from Al, Cu, and stainless steel (SAE 304) surfaces, which are common plasma chamber materials, is predominantly caused by radiation emitted from plasma with energies between 8 eV and 1 keV. Characteristic X-ray emission and bremsstrahlung from plasma have a negligible contribution to the photoelectron emission. It is estimated from the measured data that the maximum conceivable photoelectron flux from plasma chamber walls is on the order of 10% of the estimated total electron losses from the plasma.

  19. Optically controlled low-power on-off mode resonant tunneling oscillator with a heterojunction phototransistor switch.

    PubMed

    Lee, Kiwon; Park, Jaehong; Lee, Jooseok; Yang, Kyounghoon

    2015-03-15

    We report an optically controlled low-power on-off mode oscillator based on a resonant tunneling diode (RTD) that is monolithically integrated with a heterojunction phototransistor (HPT) optical switch. In order to achieve a low-power operation at a wavelength of 1.55 μm an InP-based quantum-effect tunneling diode is used for microwave signal generation based on a unique negative differential conductance (NDC) characteristic of the RTD at a low applied voltage. In addition, the high-gain HPT is used for converting incident optical data to an electrical data signal. The fabricated on-off mode oscillator shows a low-power consumption of 5 mW and a high-data-rate of 1  Gb/s at an oscillation frequency of 4.7 GHz. A good energy efficiency of 5  pJ/bit has been obtained due to the low DC power consumption along with high-data-rate performance of the RTD-based optoelectronic integration scheme.

  20. Planetary resonances, bi-stable oscillation modes, and solar activity cycles

    NASA Technical Reports Server (NTRS)

    Sleeper, H. P., Jr.

    1972-01-01

    The natural resonance structure of the planets in the solar system yields resonance periods of 11.08 and 180 years. The 11.08 year period is due to resonance of the sidereal periods of the three inner planets. The 180-year period is due to synodic resonances of the four major planets. These periods are also observed in the sunspot time series. The 11-year sunspot cycles from 1 to 19 are separated into categories of positive and negative cycles, Mode 1 and Mode 2 cycles, and typical and anomalous cycles. Each category has a characteristic shape, magnitude, or duration, so that statistical prediction techniques are improved when a cycle can be classified in a given category. These categories provide evidence for bistable modes of solar oscillation. The next minimum is expected in 1977 and the next maximum in 1981 or later. These epoch values are 2.5 years later than those based on typical cycle characteristics.

  1. Focused ion beam engineered whispering gallery mode resonators with open cavity structure.

    PubMed

    Aveline, David C; Baumgartel, Lukas; Ahn, Byungmin; Yu, Nan

    2012-07-30

    We report the realization of an open cavity whispering gallery mode optical resonator, in which the circulating light traverses a free space gap. We utilize focused ion beam microfabrication to precisely cut a 10 μm wide notch into the perimeter of a crystalline disc. We have shown that this modified resonator structure supports high quality modes, and demonstrated qualify factor, Q ~/= 10(6), limited by the notch surface roughness due to the ion milling process. Furthermore, we investigated the spatial profile of the modes inside the open cavity with a microfabricated probe mechanism. This new type of resonator structure facilitates interaction of the cavity's optical field with mechanical resonators as well as individual atoms or molecules.

  2. An effective method for designing insensitive resonator of continuous-wave passively mode-locked laser.

    PubMed

    Wen, Qiao; Sun, Liqun; Wang, Yonggang; Zhang, Enyao; Tian, Qian

    2009-05-25

    An effective method for designing the insensitive resonator of a continuous-wave passively mode-locked laser is firstly presented in this paper. This method, using resonator transform circle graphic theory, is both intuitive and reliable. Theoretical results show that the resonator is suitable to obtain highly stable mode locking operation when the following two conditions are fulfilled. First, the transform circle of the terminal mirror opposite the semiconductor saturable absorber mirror (SESAM) propagates through a series of lens (including the thermal lens of the gain medium) and a small transform circle in the image space is obtained, which ensures the small spot size at the SESAM. Second, the resonator transform circles orthogonally (or nearly orthogonally) intersect at the SESAM, which ensures the spot size at the SESAM is insensitive to the external perturbation. The experimental results of the mode locking lasers show good agreement with the theoretical studies very well.

  3. Enhanced sensitivity in single-mode silicon nitride stadium resonators at visible wavelengths.

    PubMed

    Chemnitz, Mario; Schmidl, Gabriele; Schwuchow, Anka; Zeisberger, Matthias; Hübner, Uwe; Weber, Karina; Schmidt, Markus A

    2016-11-15

    The marker-free and noninvasive detection of small traces of analytes in aqueous solution using integrated optical resonators is an emerging technique within bioanalytics. Here, we present a single-mode silicon-nitride stadium resonator operating at the red edge of the visible spectrum, showing sensitivities larger than 200 nm/RIU and transmission dips with extinction ratios of more than 15 dB. We introduce a mathematical model that allows analyzing of the resonator sensitivity using the properties of the guided mode only. Large geometric parameter scans using finite element simulations show that optimal sensing conditions are achieved for TM-polarized modes close to the modal cutoff. Due to its compactness and the short operation wavelength, we anticipate applications of our resonator for integrated bioanalytics.

  4. Modeling of ICRH H-minority-driven n = 1 Resonant Modes in JET

    SciTech Connect

    N.N. Gorelenkov; M.J. Mantsinen; S.E. Sharapov; C.Z. Cheng; the JET-EFDA Contributors

    2003-08-21

    A nonperturbative code NOVA-KN (Kinetic Nonperturbative) has been developed to account for finite orbit width (FOW) effects in nonperturbative resonant modes such as the low-frequency MHD modes observed in the Joint European Torus (JET). The NOVA-KN code was used to show that the resonant modes with frequencies in the observed frequency range are ones having the characteristic toroidal precession frequency of H-minority ions. Results are similar to previous theoretical studies of fishbone instabilities, which were found to exist at characteristic precession frequencies of hot ions.

  5. Formation of long-lived resonances in hexagonal cavities by strong coupling of superscar modes

    NASA Astrophysics Data System (ADS)

    Song, Qinghai; Ge, Li; Wiersig, Jan; Cao, Hui

    2013-08-01

    The recent progresses in single crystalline wide bandgap hexagonal disk have stimulated intense research attention on pursuing ultraviolet (UV) laser diodes with low thresholds. While whispering-gallery modes based UV lasers have been successfully obtained in GaN, ZnO nanorods, and nanopillars, the reported thresholds are still very high, due to the low-quality (Q) factors of the hexagonal resonances. Here we demonstrate resonances whose Q factors can be more than two orders of magnitude higher than the hexagonal modes, promising the reduction of the energy consumption. The key to our finding is the avoided resonance crossing between superscar states along two sets of nearly degenerated triangle orbits, which leads to the formation of hexagram modes. The mode couplings suppress the field distributions at the corners and the deviations from triangle orbits simultaneously and therefore enhance the Q factors significantly.

  6. Multimode filter composed of single-mode surface acoustic wave/bulk acoustic wave resonators

    NASA Astrophysics Data System (ADS)

    Huang, Yulin; Bao, Jingfu; Tang, Gongbin; Wang, Yiling; Omori, Tatsuya; Hashimoto, Ken-ya

    2017-07-01

    This paper discusses the possibility of realizing multimode filters composed of multiple single-mode resonators by using radio frequency surface and bulk acoustic wave (SAW/BAW) technologies. First, the filter operation and design principle are given. It is shown that excellent filter characteristics are achievable by combining multiple single-mode resonators with identical capacitance ratios provided that their resonance frequencies and clamped capacitances are set properly. Next, the effect of balun performance is investigated. It is shown that the total filter performance is significantly degraded by balun imperfections such as the common-mode rejection. Then, two circuits are proposed to improve the common-mode rejection, and their effectiveness is demonstrated.

  7. Robust Vibration Suppression of Resonant Modes by Feedback Compensation Realized Using Allpass Filters

    NASA Astrophysics Data System (ADS)

    Hirose, Noriaki; Iwasaki, Makoto; Kawafuku, Motohiro; Hirai, Hiromu

    In this paper, we present a novel type of feedback compensation for achieving robust vibration suppression of resonant modes in mechatronic systems by the use of allpass filters. In most mechactronic systems, residual vibration must be sufficiently suppressed during precise positioning. In order to achieve the required vibration suppression, the proposed feedback compensation realized using allpass filters is adopted to stabilize the resonant modes without attenuating the gain and to improve the sensitivity characteristics around the resonant modes even when the plant system has high-order vibration modes and time-delay characteristics. The effectiveness of the proposed approach has been verified by carrying out numerical simulations and performing experiments using a prototype.

  8. Mode conversion of fast Alfvén waves at the ion-ion hybrid resonance

    NASA Astrophysics Data System (ADS)

    Ram, A. K.; Bers, A.; Schultz, S. D.; Fuchs, V.

    1996-05-01

    Substantial radio-frequency power in the ion-cyclotron range of frequencies can be effectively coupled to a tokamak plasma from poloidal current strap antennas at the plasma edge. If there exists an ion-ion hybrid resonance inside the plasma, then some of the power from the antenna, delivered into the plasma by fast Alfvén waves, can be mode converted to ion-Bernstein waves. In tokamak confinement fields the mode-converted ion-Bernstein waves can damp effectively and locally on electrons [A. K. Ram and A. Bers, Phys. Fluids B 3, 1059 (1991)]. The usual mode-conversion analysis that studies the propagation of fast Alfvén waves in the immediate vicinity of the ion-ion hybrid resonance is extended to include the propagation and reflection of the fast Alfvén waves on the high magnetic-field side of the ion-ion hybrid resonance. It is shown that there exist plasma conditions for which the entire fast Alfvén wave power incident on the ion-ion hybrid resonance can be converted to ion-Bernstein waves. In this extended analysis of the mode conversion process, the fast Alfvén waves can be envisioned as being coupled to an internal plasma resonator. This resonator extends from the low magnetic-field cutoff near the ion-ion hybrid resonance to the high magnetic-field cutoff. The condition for 100% mode conversion corresponds to a critical coupling of the fast Alfvén waves to this internal resonator. As an example, the appropriate plasma conditions for 100% mode conversion are determined for the Tokamak Fusion Test Reactor (TFTR) [R. Majeski et al., Proceedings of the 11th Topical Conference on RF Power in Plasmas, Palm Springs (American Institute of Physics, New York, 1995), Vol. 355, p. 63] experimental parameters.

  9. An MHD simulation study of the poloidal mode field line resonance in the Earth's dipole magnetosphere

    NASA Technical Reports Server (NTRS)

    Ding, D. Q.; Denton, . E.; Hudson, M. K.; Lysak, R. L.

    1995-01-01

    The poloidal mode field line resonance in the Earth's dipole magnetic field is investigated using cold plasma ideal MHD simulations in dipole geometry. In order to excite the poloidal mode resonance, we use either an initial or a continuous velocity perturbation to drive the system. The perturbation is localized at magnetic shell L = 7 with plasma flow in the radial direction (electric field component in the azimuthal direction). It is found that with the initial perturbation alone, no polodial mode resonance can be obtained and the initially localized perturbation spreads out across all magnetic L shells. With the continuous perturbation, oscillating near the poloidal resonance frequency, a global-scale poloidal cavity mode can be obtained. For the first time, a localized guided poloidal mode resonance is obtained when a radial component of electric field is added to the initial perturbation such that the curl of the electric field is everywhere perpendicular to the background dipole magnetic field. During the localized poloidal resonance, plasma vortices parallel/antiparallel to the background dipole magnetic field B(sub 0). This circular flow, elongated radially, results in twisting of magnetic field flux tubes, which, in turn, leads to the slowdown of the circular plasma flow and reversal of the plasma vortices. The energy associated with the localized poloidal resonance is conserved as it shifts back and forth between the oscillating plasma vortices and the alternately twisted magnetic flux tubes. In the simulations the eigenfunctions associated with the localized poloidal resonance are grid-scale singular functions. This result indicates that ideal MHD is inadequate to describe the underlying problem and nonideal MHD effects are needed for mode broadening.

  10. Investigation of fiber Bragg grating based mode-splitting resonant sensors.

    PubMed

    Campanella, Carlo Edoardo; Mastronardi, Lorenzo; De Leonardis, Francesco; Malara, Pietro; Gagliardi, Gianluca; Passaro, Vittorio M N

    2014-10-20

    In this paper, we report on theoretical investigation of split mode resonant sensors based on fiber Bragg grating (FBG) ring resonators and π-shifted fiber Bragg grating (π-FBG) ring resonators. By using a π-shifted Bragg grating ring resonator (π-FBGRR) instead of a conventional fiber Bragg grating ring resonator (FBGRR), the symmetric and antisymmetric resonance branches (i.e., the eigen-modes of the perturbed system) show peculiar and very important features that can be exploited to improve the performance of the fiber optic spectroscopic sensors. In particular, the π-FBGRR symmetric resonance branch can be taylored to have a maximum splitting sensitivity to small environmental perturbations. This optimal condition has been found around the crossing points of the two asymmetric resonance branches, by properly choosing the physical parameters of the system. Then, high sensitivity splitting mode sensors are theoretically demonstrated showing, as an example, a strain sensitivity improvement of at least one order of magnitude over the state-of-the-art.

  11. Calculation of the spectrum of whispering gallery modes in cylindrical resonators with perturbed boundary conditions

    SciTech Connect

    Dontsov, A A; Monakhov, A M; Averkiev, Nikita S

    2013-05-31

    The spectrum of whispering gallery modes for resonators with a small deformation of the boundary is calculated analytically. Cylindrical resonators with two different cross sections (segment close to a circle and segment close to a semicircle) are considered. The calculation is performed for resonators with metal boundaries, but the obtained result is a good approximation for dielectric resonators as well. The applicability limits of the found expressions for the spectra are analysed. It is shown that the spectra calculated using the obtained expressions coincide well with computer-calculated spectra. The perturbation-induces changes in the field distribution are qualitatively studied using numerical simulation. (semiconductor lasers. physics and technology)

  12. Nanoscale welding aerosol sensing based on whispering gallery modes in a cylindrical silica resonator

    PubMed Central

    Lee, Aram; Mills, Thomas; Xu, Yong

    2015-01-01

    We report an experimental technique where one uses a standard silica fiber as a cylindrical whispering gallery mode (WGM) resonator to sense airborne nanoscale aerosols produced by electric arc welding. We find that the accumulation of aerosols on the resonator surface induces a measurable red-shift in resonance frequency, and establish an empirical relation that links the magnitude of resonance shift with the amount of aerosol deposition. The WGM quality factors, by contrast, do not decrease significantly, even for samples with a large percentage of surface area covered by aerosols. Our experimental results are discussed and compared with existing literature on WGM-based nanoparticle sensing. PMID:25837078

  13. High mode volume self filtering unstable resonator applied to a short pulse XeCl laser

    NASA Astrophysics Data System (ADS)

    Luches, A.; Nassisi, V.; Perrone, M. R.; Radiotis, E.

    1989-05-01

    A high mode volume non confocal self filtering unstable resonator has been applied to a short pulse XeCl laser. Such a resonator made up of a concave mirror (focal length is 25 cm) and a convex mirror (focal length is -25 cm), has a magnification | M|=34 and a cavity length of 151 cm. A nearly diffraction limited laser beam of 5.5 mJ, 10 ns duration and with a brightness of 2.5×10 13 W cm -2 sr -1 has been obtained. These results are compared to those obtained with another self-filtering unstable resonator having the same resonator length but | M|=10.

  14. Symmetry of the spatial structure of radiation upon transverse mode locking in an astigmatic resonator laser

    SciTech Connect

    Bezotosnyi, V V; Gorbunkov, Mikhail V; Cheshev, E A; Kostryukov, P V; Tunkin, V G; Yakovlev, D V

    2009-08-31

    The influence of the astigmatic resonator parameters on the symmetry of the spatial structure of the radiation intensity is analysed upon transverse mode locking in a nonuniformly pumped laser. Conditions for the transition from the circular symmetry to its violation are found. At a fixed astigmatism of the resonator, the symmetry is determined, first of all, by the resonator length and losses. The theoretical conclusions are confirmed by the experiments with diode end-pumped Nd:YAG and Nd:YLF lasers. (resonators)

  15. Exploring the Frequency Stability Limits of Whispering Gallery Mode Resonators for Metrological Applications

    NASA Technical Reports Server (NTRS)

    Chembo, Yanne K.; Baumgartel, Lukas; Grudinin, Ivan; Strekalov, Dmitry; Thompson, Robert; Yu, Nan

    2012-01-01

    Whispering gallery mode resonators are attracting increasing interest as promising frequency reference cavities. Unlike commonly used Fabry-Perot cavities, however, they are filled with a bulk medium whose properties have a significant impact on the stability of its resonance frequencies. In this context that has to be reduced to a minimum. On the other hand, a small monolithic resonator provides opportunity for better stability against vibration and acceleration. this feature is essential when the cavity operates in a non-laboratory environment. In this paper, we report a case study for a crystalline resonator, and discuss the a pathway towards the inhibition of vibration-and acceleration-induced frequency fluctuations.

  16. Demonstration of polarization mode selection and coupling efficiency of optofluidic ring resonator lasers.

    PubMed

    Zhang, Yuanxian; Meng, Weidong; Yang, Hongyue; Chu, Yufei; Pu, Xiaoyun

    2015-11-01

    We demonstrate the polarization mode selection and the dependence of coupling efficiency on polarization state of pump light for an optofluidic ring resonator (OFRR) laser. An optical fiber is chosen to serve as the ring resonator and surrounded by rhodamine 6G dye solution of lower refractive index as the fluidic gain medium. When the ring resonator is pumped by a linearly s-polarized laser, the emitted whispering gallery mode (WGM) lasing is of parallel polarization (TM mode), while p-polarized laser excitation generates a vertically polarized lasing emission (TE mode), both TM and TE mode lasing emission coexist simultaneously if the ring resonator is pumped by the s- and p-mixed polarized light. Further investigation reveals that the lasing intensity of the TM mode is approximately twice that of the TE mode for the same pump energy density, meaning an obvious difference of coupling efficiency on the polarization state of pump light; the experimental results of coupling efficiency are well explained by an induced dipole model.

  17. Ossicular resonance modes of the human middle ear for bone and air conduction

    PubMed Central

    Homma, Kenji; Du, Yu; Shimizu, Yoshitaka; Puria, Sunil

    2009-01-01

    The mean resonance frequency of the human middle ear under air conduction (AC) excitation is known to be around 0.8–1.2 kHz. However, studies suggest that the mean resonance frequency under bone conduction (BC) excitation is at a higher frequency around 1.5–2 kHz. To identify the cause for this difference, middle-ear responses to both AC and BC excitations were measured at the umbo and lateral process of the malleus using five human cadaver temporal bones. The resonance modes identified from these measurements, along with finite element analysis results, indicate the presence of two ossicular modes below 2 kHz. The dominant mode under AC excitation is the first mode, which typically occurs around 1.2 kHz and is characterized by a “hinging” ossicular motion, whereas the dominant mode under BC excitation is the second mode, which typically occurs around 1.7 kHz and is characterized by a “pivoting” ossicular motion. The results indicate that this second mode is responsible for the translational component in the malleus handle motion. The finding is also consistent with the hypothesis that a middle-ear structural resonance is responsible for the prominent peak seen at 1.5–2 kHz in BC limit data. PMID:19206873

  18. Engineering, design and prototype tests of a 3.9 GHz transverse-mode superconducting cavity for a radiofrequency-separated kaon beam

    SciTech Connect

    Mark S.Champion et al.

    2001-07-03

    A research and development program is underway to construct superconducting cavities to be used for radiofrequency separation of a Kaon beam at Fermilab. The design calls for installation of twelve 13-cell cavities operating in the 3.9 GHz transverse mode with a deflection gradient of 5 MV/m. They present the mechanical, cryogenic and vacuum design of the cavity, cryomodule, rf power coupler, cold tuner and supporting hardware. The electromagnetic design of the cavity is presented in a companion paper by Wanzenberg and McAshan. The warm tuning system (for field flatness) and the vertical test system is presented along with test results of bench measurements and cold tests on single-cell and five-cell prototypes.

  19. 1.55 μm hydrogen cyanide optical frequency-stabilized and 10 GHz repetition-rate-stabilized mode-locked fiber laser.

    PubMed

    Yoshida, Masato; Yoshida, Kazuki; Kasai, Keisuke; Nakazawa, Masataka

    2016-10-17

    We describe a 1.55 μm hydrogen cyanide (HCN) optical frequency and repetition rate stabilized mode-locked fiber laser, where the optical frequency was locked to the P(10) HCN absorption line and the repetition rate was locked to 9.95328 GHz by using a microwave phase-locked loop. The optical frequency stability of the laser reached 5 x 10-11 with an integration time τ of 1 s. With a bidirectional pumping scheme, the laser output power reached 64.6 mW. To obtain a short pulse train, the average dispersion in the cavity was managed so that it was zero around 1.55 μm, resulting in a 0.95 ps pulse train. In addition, the stabilization of the optical frequency and the repetition rate, meant that the entire spectral profile remained the same for 24 hours.

  20. Microfiber-based few-layer MoS2 saturable absorber for 2.5 GHz passively harmonic mode-locked fiber laser.

    PubMed

    Liu, Meng; Zheng, Xu-Wu; Qi, You-Li; Liu, Hao; Luo, Ai-Ping; Luo, Zhi-Chao; Xu, Wen-Cheng; Zhao, Chu-Jun; Zhang, Han

    2014-09-22

    We reported on the generation of high-order harmonic mode-locking in a fiber laser using a microfiber-based molybdenum disulfide (MoS(2)) saturable absorber (SA). Taking advantage of both the saturable absorption and large third-order nonlinear susceptibilities of the few-layer MoS(2), up to 2.5 GHz repetition rate HML pulse could be obtained at a pump power of 181 mW, corresponding to 369th harmonic of fundamental repetition frequency. The results provide the first demonstration of the simultaneous applications of both highly nonlinear and saturable absorption effects of the MoS(2), indicating that the microfiber-based MoS(2) photonic device could serve as high-performance SA and highly nonlinear optical component for application fields such as ultrafast nonlinear optics.

  1. Observing electron spin resonance between 0.1 and 67 GHz at temperatures between 50 mK and 300 K using broadband metallic coplanar waveguides

    NASA Astrophysics Data System (ADS)

    Wiemann, Yvonne; Simmendinger, Julian; Clauss, Conrad; Bogani, Lapo; Bothner, Daniel; Koelle, Dieter; Kleiner, Reinhold; Dressel, Martin; Scheffler, Marc

    2015-05-01

    We describe a fully broadband approach for electron spin resonance (ESR) experiments, where it is possible to tune not only the magnetic field but also the frequency continuously over wide ranges. Here, a metallic coplanar transmission line acts as compact and versatile microwave probe that can easily be implemented in different cryogenic setups. We perform ESR measurements at frequencies between 0.1 and 67 GHz and at temperatures between 50 mK and room temperature. Three different types of samples (Cr3+ ions in ruby, organic radicals of the nitronyl-nitroxide family, and the doped semiconductor Si:P) represent different possible fields of application for the technique. We demonstrate that an extremely large phase space in temperature, magnetic field, and frequency for ESR measurements, substantially exceeding the range of conventional ESR setups, is accessible with metallic coplanar lines.

  2. High-spectral-contrast symmetric modes in photonic crystal dual nanobeam resonators

    SciTech Connect

    Abbaslou, Siamak; Gatdula, Robert; Lu, Ming; Stein, Aaron; Soref, Richard A.; Jiang, Wei

    2016-06-20

    Here, we demonstrate accurate control of mode symmetry in suspended dual-nanobeam resonators on a silicon-on-insulator chip. Each nanobeam consists of a Fabry-Perot nanocavity bounded by tapered 1-D photonic crystals. Even and odd cavity-modes are formed due to lateral evanescent coupling between the two nanobeams. The odd cavity-mode can be excited by mode-symmetry-transforming Mach-Zehnder couplers. Modal contrasts over 27 dB are measured in fabricated structures. The influence of the optical field in the middle air slot on the background transmission and quality factors is discussed. The observed peak wavelength separations of the modes at various nanobeam spacings are in good agreement with simulation results. These nanobeam resonators are potentially useful in applications, such as ultrafast all-optical modulation, filtering, and switching.

  3. High-spectral-contrast symmetric modes in photonic crystal dual nanobeam resonators

    SciTech Connect

    Abbaslou, Siamak; Gatdula, Robert; Lu, Ming; Stein, Aaron; Soref, Richard A.; Jiang, Wei

    2016-06-20

    Here, we demonstrate accurate control of mode symmetry in suspended dual-nanobeam resonators on a silicon-on-insulator chip. Each nanobeam consists of a Fabry-Perot nanocavity bounded by tapered 1-D photonic crystals. Even and odd cavity-modes are formed due to lateral evanescent coupling between the two nanobeams. The odd cavity-mode can be excited by mode-symmetry-transforming Mach-Zehnder couplers. Modal contrasts over 27 dB are measured in fabricated structures. The influence of the optical field in the middle air slot on the background transmission and quality factors is discussed. The observed peak wavelength separations of the modes at various nanobeam spacings are in good agreement with simulation results. These nanobeam resonators are potentially useful in applications, such as ultrafast all-optical modulation, filtering, and switching.

  4. How Natural Evaporation Temporally Self-Tunes an Oscillating Sessile Droplet To Resonate at Different Modes.

    PubMed

    Sanyal, Apratim; Basu, Saptarshi

    2016-05-17

    We report the dynamics and underlying physics of evaporation driven transitions and autotuning of oscillation modes in sessile droplets subject to substrate perturbations. We have shown that evaporation controls temporal transition of the oscillation mode with a spatially downward shift of nodes (surface locations with zero displacement) toward the three-phase contact line. We have explained the physical mechanism using two parameters: the first quantifies evaporation driven tuning for resonance detection, and the second parameter characterizes mode lifetime which is found to be governed by evaporation dynamics. It is desirable to achieve autotuning of the oscillation modes in sessile droplets that essentially self-evolves in a spatiotemporal manner with continued evaporation. The insights suggest control of mode resonances is possible, which in turn will allow precision manipulations at droplet scale crucial for many applications such as surface patterning and others.

  5. A Rossby whistle: A resonant basin mode observed in the Caribbean Sea

    NASA Astrophysics Data System (ADS)

    Hughes, Chris W.; Williams, Joanne; Hibbert, Angela; Boening, Carmen; Oram, James

    2016-07-01

    We show that an important source of coastal sea level variability around the Caribbean Sea is a resonant basin mode. The mode consists of a baroclinic Rossby wave which propagates westward across the basin and is rapidly returned to the east along the southern boundary as coastal shelf waves. Almost two wavelengths of the Rossby wave fit across the basin, and it has a period of 120 days. The porous boundary of the Caribbean Sea results in this mode exciting a mass exchange with the wider ocean, leading to a dominant mode of bottom pressure variability which is almost uniform over the Grenada, Venezuela, and Colombia basins and has a sharp spectral peak at 120 day period. As the Rossby waves have been shown to be excited by instability of the Caribbean Current, this resonant mode is dynamically equivalent to the operation of a whistle.

  6. High-spectral-contrast symmetric modes in photonic crystal dual nanobeam resonators

    DOE PAGES

    Abbaslou, Siamak; Gatdula, Robert; Lu, Ming; ...

    2016-06-20

    Here, we demonstrate accurate control of mode symmetry in suspended dual-nanobeam resonators on a silicon-on-insulator chip. Each nanobeam consists of a Fabry-Perot nanocavity bounded by tapered 1-D photonic crystals. Even and odd cavity-modes are formed due to lateral evanescent coupling between the two nanobeams. The odd cavity-mode can be excited by mode-symmetry-transforming Mach-Zehnder couplers. Modal contrasts over 27 dB are measured in fabricated structures. The influence of the optical field in the middle air slot on the background transmission and quality factors is discussed. The observed peak wavelength separations of the modes at various nanobeam spacings are in good agreementmore » with simulation results. These nanobeam resonators are potentially useful in applications, such as ultrafast all-optical modulation, filtering, and switching.« less

  7. High precision particle mass sensing using microchannel resonators in the second vibration mode

    SciTech Connect

    Lee, Jungchul; Bryan, Andrea K.; Manalis, Scott R.

    2011-02-15

    An intrinsic uncertainty in particle mass sensing with the suspended microchannel resonator results from variation in a particle's position near the free end of the resonator. To circumvent this error we employ the second flexural bending mode. This mode exhibits additional frequency peaks while particles pass over the antinode, a point where the frequency shift is insensitive to the lateral position of the particle. We measure polystyrene beads with the first and second modes and confirm that the second mode sensing provides a narrower mass histogram. For 3 {mu}m diameter beads, second mode sensing at the antinode improves the coefficient of variation in buoyant mass from 1.76% to 1.05% for population measurements and from 1.40% to 0.53% for a single trapped particle.

  8. Resonant field amplification with feedback-stabilized regime in current driven resistive wall mode

    SciTech Connect

    Liu Yueqiang; In, Y.; Okabayashi, M.

    2010-07-15

    The stability and resonant field response of current driven resistive wall modes are numerically studied for DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] low pressure plasmas. The resonant field response of the feedback-stabilized resistive wall mode is investigated both analytically and numerically, and compared with the response from intrinsically stable or marginally stable modes. The modeling qualitatively reproduces the experimental results. Furthermore, based on some recent results and on the indirect numerical evidence in this work, it is suggested that the mode stability behavior observed in DIII-D experiments is due to the kink-peeling mode stabilization by the separatrix geometry. The phase inversion radius of the computed plasma displacement does not generally coincide with the radial locations of rational surfaces, also supporting experimental observations.

  9. A 2.45 GHz electron cyclotron resonance proton ion source and a dual-lens low energy beam transporta)

    NASA Astrophysics Data System (ADS)

    Zhang, W. H.; Ma, H. Y.; Yang, Y.; Wu, Q.; Zhang, X. Z.; Wang, H.; Ma, B. H.; Feng, Y. C.; Fang, X.; Guo, J. W.; Cao, Y.; Li, X. X.; Zhu, Y. H.; Li, J. Y.; Sha, S.; Lu, W.; Lin, S. H.; Guo, X. H.; Zhao, H. Y.; Sun, L. T.; Xie, D. Z.; Peng, S. X.; Liu, Z. W.; Zhao, H. W.

    2012-02-01

    The structure and preliminary commissioning results of a new 2.45 GHz ECR proton ion source and a dual-lens low energy beam transport (LEBT) system are presented in this paper. The main magnetic field of the ion source is provided by a set of permanent magnets with two small electro-solenoid magnets at the injection and the extraction to fine tune the magnetic field for better microwave coupling. A 50 keV pulsed proton beam extracted by a three-electrode mechanism passes through the LEBT system of length of 1183 mm. This LEBT consists of a diagnosis chamber, two Glaser lenses, two steering magnets, and a final beam defining cone. A set of inner permanent magnetic rings is embedded in each of the two Glaser lenses to produce a flatter axial-field to reduce the lens aberrations.

  10. A 2.45 GHz electron cyclotron resonance proton ion source and a dual-lens low energy beam transport

    SciTech Connect

    Zhang, W. H.; Ma, H. Y.; Wu, Q.; Zhang, X. Z.; Wang, H.; Ma, B. H.; Feng, Y. C.; Fang, X.; Guo, J. W.; Li, X. X.; Zhu, Y. H.; Li, J. Y.; Guo, X. H.; Zhao, H. Y.; Sun, L. T.; Xie, D. Z.; Liu, Z. W.; Zhao, H. W.; Yang, Y.; Cao, Y.; and others

    2012-02-15

    The structure and preliminary commissioning results of a new 2.45 GHz ECR proton ion source and a dual-lens low energy beam transport (LEBT) system are presented in this paper. The main magnetic field of the ion source is provided by a set of permanent magnets with two small electro-solenoid magnets at the injection and the extraction to fine tune the magnetic field for better microwave coupling. A 50 keV pulsed proton beam extracted by a three-electrode mechanism passes through the LEBT system of length of 1183 mm. This LEBT consists of a diagnosis chamber, two Glaser lenses, two steering magnets, and a final beam defining cone. A set of inner permanent magnetic rings is embedded in each of the two Glaser lenses to produce a flatter axial-field to reduce the lens aberrations.

  11. Resonator stability and higher-order modes in free-electron laser oscillators

    NASA Astrophysics Data System (ADS)

    Pathak, Abhishek; Krishnagopal, Srinivas

    2014-08-01

    Three-dimensional simulation codes genesis and opc are used to investigate the dependence of the resonator stability of free-electron laser (FEL) oscillators on the stability parameter, laser wavelength, outcoupling hole size and mirror tilt. We find that to have stable lasing over a wide range of wavelengths, the FEL cavity configuration should be carefully chosen. Broadly, the concentric configuration gives near-Gaussian modes and the best performance. At intermediate configurations the dominant mode often switches to a higher-order mode, which kills lasing. For the same reason, the outcoupled power can also be less. We have constructed a simple analytic model to study resonator stability which gives results that are in excellent agreement with the simulations. This suggests that modes in FEL oscillators are determined more by the cavity configuration and radiation propagation than by the details of the FEL interaction. We find (as in experiments at the CLIO FEL) that tilting the mirror can, for some configurations, lead to more outcoupled power than a perfectly aligned mirror because the mode is now a more compact higher-order mode, which may have implications for the mode quality for user experiments. Finally, we show that the higher-order mode obtained is usually a single Gauss-Laguerre mode, and therefore it should be possible to filter out the mode using suitable intracavity elements, leading to better FEL performance.

  12. MEMS switching of contour-mode aluminum nitride resonators for switchable and reconfigurable radio frequency filters

    NASA Astrophysics Data System (ADS)

    Nordquist, Christopher D.; Branch, Darren W.; Pluym, Tammy; Choi, Sukwon; Nguyen, Janet H.; Grine, Alejandro; Dyck, Christopher W.; Scott, Sean M.; Sing, Molly N.; Olsson, Roy H., III

    2016-10-01

    Switching of transducer coupling in aluminum nitride contour-mode resonators provides an enabling technology for future tunable and reconfigurable filters for multi-function RF systems. By using microelectromechanical capacitive switches to realize the transducer electrode fingers, coupling between the metal electrode finger and the piezoelectric material is modulated to change the response of the device. On/off switched width extensional resonators with an area of  <0.2 mm2 demonstrate a Q of 2000, K 2 of 0.72, and  >24 dB switching ratio at a resonator center frequency of 635 MHz. Other device examples include a 63 MHz resonator with switchable impedance and a 470 MHz resonator with 127 kHz of fine center frequency tuning accomplished by mass loading of the resonator with the MEMS switches.

  13. Ten Ghz YBa2Cu3O(7-Delta) Superconducting Ring Resonators on NdGaO3 Substrates

    NASA Technical Reports Server (NTRS)

    To, H. Y.; Valco, G. J.; Bhasin, K. B.

    1993-01-01

    YBa2Cu3O(7-delta) thin films were formed on NdGaO3 substrates by laser ablation. Critical temperatures greater than 89 K and critical current densities exceeding 2 x 10(exp 8) Acm(sub -2) at 77 K were obtained. The microwave performance of films patterned into microstrip ring resonators with gold ground planes was measured. An unloaded quality factor six times larger than that of a gold resonator of identical geometry was achieved. The unloaded quality factor decreased below 70 K for both the superconducting and gold resonators due to increasing dielectric losses in the substrate. The temperature dependence of the loss tangent of NdGaO3 was extracted from the measurements.

  14. Ten Ghz YBa2Cu3O(7-Delta) Superconducting Ring Resonators on NdGaO3 Substrates

    NASA Technical Reports Server (NTRS)

    To, H. Y.; Valco, G. J.; Bhasin, K. B.

    1993-01-01

    YBa2Cu3O(7-delta) thin films were formed on NdGaO3 substrates by laser ablation. Critical temperatures greater than 89 K and critical current densities exceeding 2 x 10(exp 8) Acm(sub -2) at 77 K were obtained. The microwave performance of films patterned into microstrip ring resonators with gold ground planes was measured. An unloaded quality factor six times larger than that of a gold resonator of identical geometry was achieved. The unloaded quality factor decreased below 70 K for both the superconducting and gold resonators due to increasing dielectric losses in the substrate. The temperature dependence of the loss tangent of NdGaO3 was extracted from the measurements.

  15. Circularly polarized microwaves for magnetic resonance study in the GHz range: Application to nitrogen-vacancy in diamonds

    SciTech Connect

    Mrózek, M. Rudnicki, D. S.; Gawlik, W.; Mlynarczyk, J.

    2015-07-06

    The ability to create time-dependent magnetic fields of controlled polarization is essential for many experiments with magnetic resonance. We describe a microstrip circuit that allows us to generate strong magnetic field at microwave frequencies with arbitrary adjusted polarization. The circuit performance is demonstrated by applying it to an optically detected magnetic resonance and Rabi nutation experiments in nitrogen-vacancy color centers in diamond. Thanks to high efficiency of the proposed microstrip circuit and degree of circular polarization of 85%; it is possible to address the specific spin states of a diamond sample using a low power microwave generator. The circuit may be applied to a wide range of magnetic resonance experiments with a well-controlled polarization of microwaves.

  16. Selective enhancement of individual cantilever high resonance modes

    NASA Astrophysics Data System (ADS)

    Penedo, Marcos; Hormeño, Silvia; Prieto, Patricia; Alvaro, Raquel; Anguita, José; Briones, Fernando; Luna, Mónica

    2015-12-01

    Multifrequency atomic force microscopy (AFM) in liquid media where several eigenmodes or harmonics are simultaneously excited is improving the performance of the scanning probe techniques in biological studies. As a consequence, an important effort is being made to search for a reliable, efficient and strong cantilever high mode excitation method that operates in liquids. In this work we present (theoretical and experimentally) a technique for improving the efficiency of the most common excitation methods currently used in AFM operated in liquids: photothermal, torque (MAC Mode™) and magnetostriction. By etching specific areas of the cantilever coating, the oscillation amplitude (both flexural and torsional) of each specific eigenmode increases, leading to an improvement in signal to noise ratio of the multifrequency techniques. As an alternative, increment in high mode oscillation amplitude is also obtained by Ga+ ion implantation in the specific areas of the magnetic material.

  17. High quality factor mg-scale silicon mechanical resonators for 3-mode optoacoustic parametric amplifiers

    NASA Astrophysics Data System (ADS)

    Torres, F. A.; Meng, P.; Ju, L.; Zhao, C.; Blair, D. G.; Liu, K.-Y.; Chao, S.; Martyniuk, M.; Roch-Jeune, I.; Flaminio, R.; Michel, C.

    2013-07-01

    Milligram-scale resonators have been shown to be suitable for the creation of 3-mode optoacoustic parametric amplifiers, based on a phenomena first predicted for advanced gravitational-wave detectors. To achieve practical optoacoustic parametric devices, high quality factor resonators are required. We present millimetre-scale silicon resonators designed to exhibit a torsional vibration mode with a frequency in the 105-106 Hz range, for observation of 3-mode optoacoustic interactions in a compact table-top system. Our design incorporates an isolation stage and minimizes the acoustic loss from optical coating. We observe a quality factor of 7.5 × 105 for a mode frequency of 401.5 kHz, at room temperature and pressure of 10-3 Pa. We confirmed the mode shape by mapping the amplitude response across the resonator and comparing to finite element modelling. This study contributes to the development of 3-mode optoacoustic parametric amplifiers for use in novel high-sensitivity signal transducers and quantum measurement experiments.

  18. First report of resonant interactions between whistler mode waves in the Earth's magnetosphere

    NASA Astrophysics Data System (ADS)

    Gao, Xinliang; Lu, Quanming; Wang, Shui

    2017-06-01

    Nonlinear physics related to whistler mode waves in the Earth's magnetosphere are now becoming a hot topic. In this letter, based on Time History of Events and Macroscale Interactions during Substorms waveform data, we report several interesting whistler mode wave events, where the upper band whistler mode waves are believed to be generated through the nonlinear wave-wave coupling between two lower band waves. This is the first report on resonant interactions between whistler mode waves in the Earth's magnetosphere. In these events, the two lower band whistler mode waves are observed to have oppositely propagating directions, while the generated upper band wave has the same propagating direction as the lower band wave with the relatively higher frequency. Moreover, the wave normal angle of the excited upper band wave is usually larger than those of two lower band whistler mode waves. Our results reveal the large diversity of the evolution of whistler mode waves in the Earth's magnetosphere.

  19. Non-resonant fishbone-like modes in tokamak plasmas with reversed magnetic shear

    NASA Astrophysics Data System (ADS)

    Wang, Xian-Qu; Wang, Xiao-Gang

    2016-03-01

    Energetic ion excited non-resonant fishbone-like modes (FLMs) of m / n  >  1 is investigated for reversed magnetic shear configurations. It is found that the mode can be destabilized by trapped fast ions with a similar excitation mechanism as m / n  =  1 fishbones but with a local interchange-like mode structure, which is in agreement with previous experiments (Toi et al 1999 Nucl. Fusion 39 1929). The dispersion relation of the mode is derived for m / n  >  1. The radial mode structure is then studied by numerically solving the eigenvalue equation. Effects of on/off-axis heating, the width of the particle distribution, the beam energy and the energy distribution on the mode are discussed in detail. Nonlinear analysis of the mode is also carried out by a modified predator-prey model.

  20. The Rossby whistle: A resonant basin mode in the Caribbean Sea.

    NASA Astrophysics Data System (ADS)

    Hughes, Christopher W.; Williams, Joanne; Hibbert, Angela; Boening, Carmen; Oram, James

    2016-04-01

    We present a a leaky, resonant Rossby basin mode in the Caribbean Sea, excited by instability of the Caribbean Current. The mode is seen at the surface as westward-propagating Rossby waves with period 120 days, but it is most distinctive in ocean bottom pressure where it is seen in both observations and in a wide variety of ocean models. This bottom pressure mode is a product of the leakiness of the basin, which allows for mass exchange with the surrounding ocean. The mode is found to dominate sea level variability on parts of the South American coast.

  1. Resonators for solid-state lasers with large-volume fundamental mode and high alignment stability

    SciTech Connect

    Magni, V.

    1986-01-01

    Resonators containing a focusing rod are thoroughly analyzed. It is shown that, as a function of the dioptric power of the rod, two stability zones of the same width exist and that the mode volume in the rod always presents a stationary point. At this point, the output power is insensitive to the focal length fluctuations, and the mode volume inside the rod is inversely proportional to the range of the input power for which the resonator is stable. The two zones are markedly different with respect to misalignment sensitivity, which is, in general, much greater in one zone than in the other. Two design procedures are presented for monomode solid-state laser resonators with large mode volume and low sensitivity both to focal length fluctuations and to misalignment.

  2. Visualization of Vibrational Modes in Real Space by Tip-Enhanced Non-Resonant Raman Spectroscopy.

    PubMed

    Duan, Sai; Tian, Guangjun; Luo, Yi

    2016-01-18

    We present a general theory to model the spatially resolved non-resonant Raman images of molecules. It is predicted that the vibrational motions of different Raman modes can be fully visualized in real space by tip-enhanced non-resonant Raman scattering. As an example, the non-resonant Raman images of water clusters were simulated by combining the new theory and first-principles calculations. Each individual normal mode gives rise its own distinct Raman image, which resembles the expected vibrational motions of the atoms very well. The characteristics of intermolecular vibrations in supermolecules could also be identified. The effects of the spatial distribution of the plasmon as well as nonlinear scattering processes were also addressed. Our study not only suggests a feasible approach to spatially visualize vibrational modes, but also provides new insights in the field of nonlinear plasmonic spectroscopy.

  3. Selective excitation of high-Q resonant modes in a bottle/quasi-cylindrical microresonator

    NASA Astrophysics Data System (ADS)

    Dong, Yongchao; Jin, Xueying; Wang, Keyi

    2016-08-01

    We fabricate a bottle/quasi-cylindrical microresonator by using a fusion splicer. This method does not require a real-time control of the translation stages and can easily fabricate a resonator with expected size and shape. Selective excitation of whispering gallery modes (WGMs) in the resonator is realized with a fiber taper coupled at various positions of the resonator along the bottle axis. Most importantly, we obtain a clean and regular spectrum with very high quality factor (Q) modes up to 3.1×107 in the quasi-cylindrical region of the resonator. Moreover, we package the coupling system into a whole device that can be moved freely. The vibration performance tests of the packaged device show that the coupling system with the taper coupled at the quasi-cylindrical region has a remarkable anti-vibration ability. The portability and robustness of the device make it attractive in practical applications.

  4. Bifurcation, mode coupling and noise in a nonlinear multimode superconducting microwave resonator

    NASA Astrophysics Data System (ADS)

    Tancredi, G.; Ithier, G.; Meeson, P. J.

    2013-08-01

    The addition of nonlinearity to an harmonic resonator provides a route to complex dynamical behaviour of resonant modes, including coupling between them. We present a superconducting device that makes use of the nonlinearity of Josephson junctions to introduce a controlled, tunable, nonlinear inductance to a thin film coplanar waveguide resonator. Considering the device as a potential quantum optical component in the microwave regime, we create a sensitive bifurcation amplifier and then demonstrate spectroscopy of other resonant modes via the intermode coupling. We find that the sensitivity of the device approaches within a factor two quantitative agreement with a quantum model by Dykman but is limited by a noise that has its source(s) on-chip.

  5. A branch of energetic-particle driven geodesic acoustic modes due to magnetic drift resonance

    NASA Astrophysics Data System (ADS)

    Sasaki, M.; Kasuya, N.; Itoh, K.; Hallatschek, K.; Lesur, M.; Kosuga, Y.; Itoh, S.-I.

    2016-10-01

    Eigenmode analysis of geodesic acoustic modes (GAMs) driven by fast ions is performed, based on a set of gyrokinetic equations. Resonance to the magnetic drift of the fast ions can destabilize GAMs. A new branch is found in the family of GAMs, whose frequency is close to the magnetic drift frequency of the fast ions. The poloidal eigenfunction of this branch has bump structures in the poloidal direction where the resonance of the magnetic drift with the mode is strong. The ion heating rate by the GAMs is evaluated in the framework of quasi-linear theory. The heating is localized poloidally around the resonance locations. Owing to the bumps in the eigenfunction, the magnitude of the heating is much larger than that estimated without the magnetic drift resonance.

  6. Coherent spectroscopy of rare-earth-metal-ion-doped whispering-gallery-mode resonators

    SciTech Connect

    McAuslan, D. L.; Korystov, D.; Longdell, J. J.

    2011-06-15

    We perform an investigation into the properties of Pr{sup 3+}:Y{sub 2}SiO{sub 5} whispering-gallery-mode resonators as a first step toward achieving the strong coupling regime of cavity QED with rare-earth-metal-ion-doped crystals. Direct measurement of cavity QED parameters are made using photon echoes, giving good agreement with theoretical predictions. By comparing the ions at the surface of the resonator to those in the center, it is determined that the physical process of making the resonator does not negatively affect the properties of the ions. Coupling between the ions and resonator is analyzed through the observation of optical bistability and normal-mode splitting.

  7. Enhancing detection sensitivity of metallic nanostructures by resonant coupling mode and spectral integration analysis.

    PubMed

    Lin, En-Hung; Tsai, Wan-Shao; Lee, Kuang-Li; Lee, Ming-Chang M; Wei, Pei-Kuen

    2014-08-11

    We report a simple method to efficiently improve the detection limit of surface plasmon resonance in periodic metallic nanostructures by using small angle illumination and spectral integration analysis. The large-area gold nanoslit arrays were fabricated by thermal-annealing template-stripping method with a slit width of 60 nm and period of 500 nm. The small angle illumination induced a resonant coupling between surface plasmon mode and substrate mode. It increased ~2.24 times intensity sensitivity at 5.5° incident angle. The small-angle illumination also resulted in multiple resonant peaks. The spectral integration method integrated all changes near the resonant peaks and increased the signal to noise ratio about 5 times as compared to single-wavelength intensity analysis. Combining both small angle and spectral integration, the detection limit was increased to one order of magnitude. The improvement of the detection limit for antigen-antibody interactions was demonstrated.

  8. Transverse waveguide mode suppression for Pt-electrode SAW resonators on quartz and LGS.

    PubMed

    Meulendyk, Bennett J; Pereira da Cunha, Mauricio

    2011-12-01

    SAW resonators on ST-X quartz and langasite (LGS) [0°, 144°, 24°] are currently being used for hydrogen fluoride (HF) vapor sensing and high-temperature sensing, respectively. For these applications, the use of Pt-based electrodes allows the resonators to withstand the targeted harsh environments. This work reveals that for Pt-electrode resonators with conventional short-circuit gratings on the aforementioned quartz and LGS orientations, acoustic energy leaks from the grating region to the bus bars, thus degrading the resonator response. To resolve this problem, this paper proposes and implements open-circuit gratings for resonators fabricated with these substrate/metal combinations. The open-circuit gratings guide the acoustic energy within the grating region, resulting in greater quality factors and reduced losses in the resonator response. In addition, scalar potential theory is utilized in this work to identify transverse waveguide modes in the responses of open-circuit grating resonators on quartz and LGS. A transverse waveguide mode dispersion relation was derived to extend the scalar potential theory to account for asymmetry in the slowness curve around the propagation direction. This is the case for several commonly used LGS orientations, in particular LGS [0°, 144°, 24°]. Finally, this work addresses spurious transverse mode mitigation by scaling both the transducer's grating aperture and electrode overlap width. Open circuit grating resonators with appropriately scaled transducer designs were fabricated and tested, resulting in a 71% increase in quality factor and a spurious mode rejection of over 26 dBc for Pt-electrode devices on ST-X quartz. This progress directly translates into better frequency resolution and increased dynamic range for HF vapor sensors and high-temperature SAW devices.

  9. Resonant and non-resonant internal kink modes excited by the energetic electrons on HL-2A tokamak

    NASA Astrophysics Data System (ADS)

    Yu, L. M.; Chen, W.; Jiang, M.; Shi, Z. B.; Ji, X. Q.; Ding, X. T.; Li, Y. G.; Ma, R. R.; Shi, P. W.; Song, S. D.; Yuan, B. S.; Zhou, Y.; Ma, R.; Song, X. M.; Dong, J. Q.; Xu, M.; Liu, Y.; Yan, L. W.; Yang, Q. W.; Xu, Y. H.; Duan, X. R.; HL-2A Team

    2017-03-01

    Strong resonant and non-resonant internal kink modes (abbreviated as RKs and NRKs, respectively), which are also called resonant and non-resonant fishbones, are observed on HL-2A tokamak with high-power ECRH  +  ECCD‑ (or ECRH) and ECRH  +  ECCD+, respectively. (‘Resonant’ derives from the existence of q  =  1 surface (the resonant surface), and ‘non-resonant’ originates from the absence of q  =  1 surface ({{q}\\text{min}}>1 ). ECCD+ and ECCD‑ mean the driving direction of energetic electrons is the same and opposite to plasma current, respectively.) RK has features of periodic strong bursting amplitude and rapid chirping-down frequency, but NRK usually has the saturated amplitude, slow changed or constant frequency and long-lasting time. The NRK excited by energetic electrons is found for the first time. The reversed q-profiles are formed, and q min decreases during plasma current ramp-up. The value of q min is slightly smaller and a bit bigger than unity for RK and NRK conditions, respectively. The internal kink mode (IKM) structures of RKs and NRKs are confirmed by the ECEI system. Although there are different current drive directions of ECCD for excitation of RK and NRK, they all propagate in electron diamagnetic directions in poloidal. The radial mode structures, frequency and growth rate for IKMs are obtained by solving the dispersion relationship. The NRK is stable when q min is larger than a certain value, and with the decreasing q min the frequency drops, but the growth rate almost keeps constant when {{q}\\text{min}}>1 . This result is in agreement with experimental observation. Studying IKMs excited by energetic electrons can provide important experimental experiences for ITER, because the NRKs may be excited by high-power non-inductive drive of ECCD or ECRH in the operation of hybrid scenarios.

  10. Comparative research on the methods for measuring the mode deflection angle of cylindrical resonator gyroscope

    NASA Astrophysics Data System (ADS)

    Wang, Kai; Fan, Zhenfang; Wang, Dongya; Wang, Yanyan; Pan, Yao; Qu, Tianliang; Xu, Guangming

    2016-10-01

    The existence of mode deflection angle in the cylindrical resonator gyroscope (CRG) leads to the signal drift on the detecting nodes of the gyro vibration and significantly decreases the performance of the CRG. Measuring the mode deflection angle efficiently is the foundation of tuning for the imperfect cylindrical shell resonator. In this paper, an optical method based on the measuring gyroscopic resonator's vibration amplitude with the laser Doppler vibrometer and an electrical method based on measuring the output voltage of the electrodes on the resonator are both presented to measure the mode deflection angle. Comparative experiments were implemented to verify the methodology and the results show that both of the two methods could recognize the mode deflection angle efficiently. The precision of the optical method relies on the number and position of testing points distributed on the resonator. The electrical method with simple circuit shows high accuracy of measuring in a less time compared to the optical method and its error source arises from the influence of circuit noise as well as the inconsistent distribution of the piezoelectric electrodes.

  11. Special optical fiber for temperature sensing based on cladding-mode resonance.

    PubMed

    Pang, Fufei; Xiang, Wenchao; Guo, Hairun; Chen, Na; Zeng, Xianglong; Chen, Zhenyi; Wang, Tingyun

    2008-08-18

    A fiber-optic temperature sensor by using a multi-cladding special fiber is presented. It works on the basis of leaky mode resonance from fiber core to outer cladding. With the thin-thickness inner cladding, the cladding mode is strongly excited and the resonant spectrum is very sensitive to the refractive index variation of coating material. By coating the special fiber with temperature-sensitive silicone, the temperature response was investigated experimentally from -20 degrees C to 80 degrees C. The results show high temperature sensitivity (240 pm/degrees C at 20 degrees C) and good repeatability.

  12. Dynamic coupling of magnetic resonance modes in pairs of mesoscopic rectangles

    NASA Astrophysics Data System (ADS)

    Swoboda, Christian; Kuhlmann, Nils; Martens, Michael; Vogel, Andreas; Meier, Guido

    2013-07-01

    We investigate the magnetization dynamics in pairs of mesoscopic permalloy (Ni80Fe20) rectangles by means of broadband-ferromagnetic resonance measurements and micromagnetic simulations. Each pair consists of two rectangles that differ in their geometry. The local effective field at each element is significantly affected by the stray field of its neighbor for small center-to-center distances between the rectangles. In antiparallel magnetization alignment, this dynamic dipolar coupling becomes prominent and anticrossing between ferromagnetic resonance modes and higher-order spin-wave modes is observed. Combination of the experimental and the simulational findings provides a comprehensive understanding of dynamically coupled rectangles.

  13. Relationship between height and width of resonance peaks in a whispering gallery mode resonator immersed in water and sucrose solutions

    NASA Astrophysics Data System (ADS)

    Teraoka, Iwao; Yao, Haibei; Huiyi Luo, Natalie

    2017-06-01

    We employed a recently developed whispering gallery mode (WGM) dip sensor made of silica to obtain spectra for many resonance peaks in water and solutions of sucrose at different concentrations and thus having different refractive indices (RI). The apparent Q factor was estimated by fitting each peak profile in the busy resonance spectrum by a Lorentzian or a sum of Lorentzians. A plot of the Q factor as a function the peak height for all the peaks analyzed indicates a straight line with a negative slope as the upper limit, for each of water and the solutions. A coupling model for a resonator and a pair of fiber tapers to feed and pick up light, developed here, supports the presence of the upper limit. We also found that the round-trip attenuation of WGM was greater than the one estimated from light absorption by water, and the difference increased with the concentration of sucrose.

  14. Near-field coupling and resonant cavity modes in plasmonic nanorod metamaterials

    NASA Astrophysics Data System (ADS)

    Song, Haojie; Zhang, Junxi; Fei, Guangtao; Wang, Junfeng; Jiang, Kang; Wang, Pei; Lu, Yonghua; Iorsh, Ivan; Xu, Wei; Jia, Junhui; Zhang, Lide; Kivshar, Yuri S.; Zhang, Lin

    2016-10-01

    Plasmonic resonant cavities are capable of confining light at the nanoscale, resulting in both enhanced local electromagnetic fields and lower mode volumes. However, conventional plasmonic resonant cavities possess large Ohmic losses at metal-dielectric interfaces. Plasmonic near-field coupling plays a key role in a design of photonic components based on the resonant cavities because of the possibility to reduce losses. Here, we study the plasmonic near-field coupling in the silver nanorod metamaterials treated as resonant nanostructured optical cavities. Reflectance measurements reveal the existence of multiple resonance modes of the nanorod metamaterials, which is consistent with our theoretical analysis. Furthermore, our numerical simulations show that the electric field at the longitudinal resonances forms standing waves in the nanocavities due to the near-field coupling between the adjacent nanorods, and a new hybrid mode emerges due to a coupling between nanorods and a gold-film substrate. We demonstrate that this coupling can be controlled by changing the gap between the silver nanorod array and gold substrate.

  15. Near-field coupling and resonant cavity modes in plasmonic nanorod metamaterials.

    PubMed

    Song, Haojie; Zhang, Junxi; Fei, Guangtao; Wang, Junfeng; Jiang, Kang; Wang, Pei; Lu, Yonghua; Iorsh, Ivan; Xu, Wei; Jia, Junhui; Zhang, Lide; Kivshar, Yuri S; Zhang, Lin

    2016-10-14

    Plasmonic resonant cavities are capable of confining light at the nanoscale, resulting in both enhanced local electromagnetic fields and lower mode volumes. However, conventional plasmonic resonant cavities possess large Ohmic losses at metal-dielectric interfaces. Plasmonic near-field coupling plays a key role in a design of photonic components based on the resonant cavities because of the possibility to reduce losses. Here, we study the plasmonic near-field coupling in the silver nanorod metamaterials treated as resonant nanostructured optical cavities. Reflectance measurements reveal the existence of multiple resonance modes of the nanorod metamaterials, which is consistent with our theoretical analysis. Furthermore, our numerical simulations show that the electric field at the longitudinal resonances forms standing waves in the nanocavities due to the near-field coupling between the adjacent nanorods, and a new hybrid mode emerges due to a coupling between nanorods and a gold-film substrate. We demonstrate that this coupling can be controlled by changing the gap between the silver nanorod array and gold substrate.

  16. Enhancement-mode Lg = 50 nm metamorphic InAlAs/InGaAs HEMTs on GaAs substrates with fmax surpassing 408 GHz

    NASA Astrophysics Data System (ADS)

    Li, Ming; Tang, Chak Wah; Li, Haiou; Lau, Kei May

    2014-09-01

    A novel self-aligned T-shaped gate enhancement-mode metamorphic In0.50Al0.50As/In0.53Ga0.47As HEMTs on GaAs substrates by MOCVD is proposed and demonstrated, utilizing an optimized multi-stage composite buffer scheme. High 2-D electron gas Hall mobility values of 9100 cm2/V s at 300 K and 38,900 cm2/V s at 77 K have been achieved. The mHEMT had a threshold voltage (Vth) of +0.22 V, a maximum drain current of 786 mA/mm and transconductance up to 1.2 S/mm at VDS = 0.5 V. The fT and fmax of 50-nm T-shaped gate devices were 305 and 408 GHz, respectively. To the knowledge of the authors, these results are the highest reported for MOCVD-grown enhancement-mode mHEMTs on GaAs substrate.

  17. Air-mode photonic crystal ring resonator on silicon-on-insulator

    PubMed Central

    Gao, Ge; Zhang, Yong; Zhang, He; Wang, Yi; Huang, Qingzhong; Xia, Jinsong

    2016-01-01

    In this report, we propose and demonstrate an air-mode photonic crystal ring resonator (PhCRR) on silicon-on-insulator platform. Air mode is utilized to confine the optical field into photonic crystal (PhC) air holes, which is confirmed by the three-dimensional finite-difference time-domain simulation. PhCRR structure is employed to enhance the light-matter interaction through combining the whispering-gallery mode resonance of ring resonator with the slow-light effect in PhC waveguide. In the simulated and measured transmission spectra of air-mode PhCRR, nonuniform free spectral ranges are observed near the Brillouin zone edge of PhC, indicating the presence of the slow-light effect. A maximum group index of 27.3 and a highest quality factor of 14600 are experimentally obtained near the band edge. Benefiting from the strong optical confinement in the PhC holes and enhanced light-matter interaction in the resonator, the demonstrated air-mode PhCRR is expected to have potential applications in refractive index sensing, on-chip light emitting and nonlinear optics by integration with functional materials. PMID:26818430

  18. Position and mode dependent optical detection back-action in cantilever beam resonators

    NASA Astrophysics Data System (ADS)

    Larsen, T.; Schmid, S.; Dohn, S.; Sader, J. E.; Boisen, A.; Villanueva, L. G.

    2017-03-01

    Optical detection back-action in cantilever resonant or static detection presents a challenge when striving for state-of-the-art performance. The origin and possible routes for minimizing optical back-action have received little attention in literature. Here, we investigate the position and mode dependent optical back-action on cantilever beam resonators. A high power heating laser (100 µW) is scanned across a silicon nitride cantilever while its effect on the first three resonance modes is detected via a low-power readout laser (1 µW) positioned at the cantilever tip. We find that the measured effect of back-action is not only dependent on position but also the shape of the resonance mode. Relevant silicon nitride material parameters are extracted by fitting finite element (FE) simulations to the temperature-dependent frequency response of the first three modes. In a second round of simulations, using the extracted parameters, we successfully fit the FEM results with the measured mode and position dependent back-action. From the simulations, we can conclude that the observed frequency tuning is due to temperature induced changes in stress. Effects of changes in material properties and dimensions are negligible. Finally, different routes for minimizing the effect of this optical detection back-action are described, allowing further improvements of cantilever-based sensing in general.

  19. Integration of Microsphere Resonators with Bioassay Fluidics for Whispering Gallery Mode Imaging

    PubMed Central

    Kim, Daniel C.; Armendariz, Kevin P.

    2013-01-01

    Whispering gallery mode resonators are small, radially symmetric dielectrics that trap light through continuous total internal reflection. The resonant condition at which light is efficiently confined within the structure is linked with refractive index, which has led to the development of sensitive label-free sensing schemes based on whispering gallery mode resonators. One resonator design uses inexpensive high index glass microspheres that offer intrinsically superior optical characteristics, but have proven difficult to multiplex and integrate with the fluidics for sample delivery and fluid exchange necessary for assay development. Recently, we introduced a fluorescence imaging approach that enables large scale multiplexing with microsphere resonators, thus removing one obstacle for assay development. Here we report an approach for microsphere immobilization that overcomes limitations arising from their integration with fluidic delivery. The approach is an adaptation of a calcium-assisted glass bonding method originally developed for microfluidic glass chip fabrication. Microspheres bonded to glass using this technique are shown to be stable with respect to fluid flow and show no detectable loss in optical performance. Measured Q-factors, for example, remain unchanged following sphere bonding to the substrate. The stability of the immobilized resonators is further demonstrated by transferring lipid films onto the immobilized spheres using the Langmuir-Blodgett technique. Bilayers of DOPC doped with GM1 were transferred onto immobilized resonators to detect the binding of cholera toxin to GM1. Binding curves generated from shifts in the whispering gallery mode resonance result in a measured Kd of 1.5 × 10−11 with a limit of detection of 3.3 pM. These results are discussed in terms of future assay development using microsphere resonators. PMID:23615457

  20. Frequency stabilization and transverse mode discrimination in injection-seeded unstable resonator TEA CO2 lasers

    NASA Technical Reports Server (NTRS)

    Ancellet, G. M.; Menzies, R. T.; Brothers, A. M.

    1987-01-01

    Longitudinal mode selection by injection has been demonstrated as a viable technique for TEA-CO2 lasers with pulse energies of a Joule or greater. Once reliable generation of single-longitudinal-mode (SLM) pulses is obtained, the characteristics and the causes of intrapulse frequency variation can be studied. These include the effect of the decaying plasma, the thermal gradient due to the energy dissipation associated with the laser mechanism itself, and the pressure shift of the center frequency of the laser transition. The use of the positive-branch unstable resonator as an efficient means of coupling a discharge with large spatial dimensions to an optical cavity mode introduces another concern: namely, what can be done to emphasize transverse mode discrimination in an unstable resonator cavity while maintaining high coupling efficiency. These issues are discussed in this paper, and relevant experimental results are included.

  1. The g-tensor of the flavin cofactor in (6-4) photolyase: a 360 GHz/12.8 T electron paramagnetic resonance study

    NASA Astrophysics Data System (ADS)

    Schnegg, A.; Kay, C. W. M.; Schleicher, E.; Hitomi, K.; Todo, T.; Möbius, K.; Weber, S.

    2006-05-01

    The g-tensor of the neutral radical form of the flavin adenine dinucleotide cofactor FADH• of (6-4) photolyase from Xenopus laevis has been determined by very high-magnetic-field/high-microwave-frequency electron-paramagnetic resonance (EPR) performed at 360 GHz/12.8 T. Due to the high spectral resolution the anisotropy of the g-tensor could be fully resolved in the frozen-solution continuous-wave EPR spectrum. By least square fittings of spectral simulations to experimental data, the principal values of the g-tensor have been established: gX = 2.00433(5), gY = 2.00368(5), gZ = 2.00218(7). A comparison of very high-field EPR data and proton and deuteron electron-nuclear double resonance measurements yielded precise information concerning the orientation of the g-tensor with respect to the molecular frame. This data allowed a comparison to be made between the principal values of the g-tensors of the FADH• cofactors of photolyases involved in the repair of two different DNA lesions: the cyclobutane pyrimidine dimer (CPD) and the (6-4) photoproduct. It was found that gX and gZ are similar in both enzymes, whereas the gY component is slightly larger in (6-4) photolyase. This result clearly shows the sensitivity of the g-tensor to subtle differences in the protein environment experienced by the flavin.

  2. Effect of a metal-dielectric structure introduced in the plasma chamber of the Frankfurt 14 GHz electron cyclotron resonance ion source

    NASA Astrophysics Data System (ADS)

    Schächter, L.; Stiebing, K. E.; Dobrescu, S.; Badescu-Singureanu, Al. I.; Schmidt, L.; Hohn, O.; Runkel, S.

    1999-02-01

    A new approach of the possibility to significantly increase the high charge state ion beams delivered by electron cyclotron resonance (ECR) ion sources by using metal-dielectric (MD) structures characterized by high secondary electron emission properties is presented. The intensities of argon ion beams extracted from the 14 GHz electron cyclotron resonance ion source of the Institut für Kernphysik (IKF) der Johann Wolfgang Goethe-Universität in Frankfurt/Main were measured when a 26 mm diam disk of a specially treated MD structure (Al-Al2O3) was introduced axially close to the ECR plasma. The Ar beam intensities and charge-state distributions obtained with this disk are compared to measurements with disks of iron and pure aluminum at the same position relative to the plasma. All measurements were performed with the disk at the plasma chamber potential. The results with the MD structure show a net shift of the beam intensity towards higher charge states as compared with the other disk materials. Enhancement factors of the beam current of up to 10 (for Ar12+) when using a MD disk compared to the output when using an aluminum disk and up to 40 (for Ar11+) when using an iron disk were measured.

  3. Modes Coupling Analysis of Surface Plasmon Polaritons Based Resonance Manipulation in Infrared Metamaterial Absorber

    PubMed Central

    Zhen, Guoshuai; Zhou, Peiheng; Luo, Xiaojia; Xie, Jianliang; Deng, Longjiang

    2017-01-01

    Surface plasmon polaritons (SPPs) and standing wave modes provide interesting and exotic properties for infrared metamaterial absorbers. Coupling of these modes promises further development in this field but restricted by the complexity of modes analysis. In this work, we investigate the general phenomenon of modes coupling supported by a metal (with grating)-dielectric-metal sandwich structure based on rigorous coupled-wave analysis (RCWA) method and experiment results. Through the analysis of fundamental modes, a new approach based on the boundary conditions is introduced to reveal the coupling mechanism and the corresponding resonance shifting phenomenon with simple but rigorous derivations. The strong coupling between SPPs excited on the dielectric-metal interfaces and rigorous modes of standing waves in the dielectric layer can be manipulated to improve the detection sensitivity of sensors and emissivity efficiency of infrared emitters. PMID:28397870

  4. Resonant translational, breathing, and twisting modes of transverse magnetic domain walls pinned at notches

    NASA Astrophysics Data System (ADS)

    Metaxas, Peter J.; Albert, Maximilian; Lequeux, Steven; Cros, Vincent; Grollier, Julie; Bortolotti, Paolo; Anane, Abdelmadjid; Fangohr, Hans

    2016-02-01

    We study resonant translational, breathing, and twisting modes of transverse magnetic domain walls pinned at notches in ferromagnetic nanostrips. We demonstrate that a mode's sensitivity to notches depends strongly on the mode's characteristics. For example, the frequencies of modes that involve lateral motion of the wall are the most sensitive to changes in the notch intrusion depth, especially at the narrow, more strongly confined end of the domain wall. In contrast, the breathing mode, whose dynamics are concentrated away from the notches is relatively insensitive to changes in the notches' sizes. We also demonstrate a sharp drop in the translational mode's frequency towards zero when approaching depinning which is confirmed, using a harmonic oscillator model, to be consistent with a reduction in the local slope of the notch-induced confining potential at its edge.

  5. Modes Coupling Analysis of Surface Plasmon Polaritons Based Resonance Manipulation in Infrared Metamaterial Absorber.

    PubMed

    Zhen, Guoshuai; Zhou, Peiheng; Luo, Xiaojia; Xie, Jianliang; Deng, Longjiang

    2017-04-11

    Surface plasmon polaritons (SPPs) and standing wave modes provide interesting and exotic properties for infrared metamaterial absorbers. Coupling of these modes promises further development in this field but restricted by the complexity of modes analysis. In this work, we investigate the general phenomenon of modes coupling supported by a metal (with grating)-dielectric-metal sandwich structure based on rigorous coupled-wave analysis (RCWA) method and experiment results. Through the analysis of fundamental modes, a new approach based on the boundary conditions is introduced to reveal the coupling mechanism and the corresponding resonance shifting phenomenon with simple but rigorous derivations. The strong coupling between SPPs excited on the dielectric-metal interfaces and rigorous modes of standing waves in the dielectric layer can be manipulated to improve the detection sensitivity of sensors and emissivity efficiency of infrared emitters.

  6. Simulation study on transverse mode of laser resonator

    NASA Astrophysics Data System (ADS)

    Zou, H.; Zhou, L. F.; Yang, Z.

    2015-08-01

    Simulation study of the stability lateral field distribution for a variety of shapes parallel-plane cavity with the Fox-Li numerical iterative method is conducted in this paper, which gives the optical field amplitude distribution and phase distribution after iterating any number of times. After calculation and simulation, we find that the strip cavity needs 245 times iterations to produce a stable field conditions, while rectangular and circular cavity need 103 and 114 times under the same condition. Finally, the user interface for simulating the field distribution of a common parallel-plane cavity is designed, which is conducive to the understanding and extensive application of the theory of laser transverse mode.

  7. Localized surface plate modes via flexural Mie resonances

    NASA Astrophysics Data System (ADS)

    Farhat, M.; Chen, P.-Y.; Guenneau, S.; Salama, K. N.; Baǧcı, H.

    2017-05-01

    Surface-plasmon polaritons are naturally generated upon excitation of metals with high-frequency electromagnetic waves. However, the concept of spoof plasmons has made it possible to generate plasmoniclike effects in microwave electrodynamics, magnetics, and even acoustics. Similarly, in this paper, the concept of localized surface plate modes (SPMs) is introduced. It is demonstrated that SPMs can be generated on a two-dimensional (clamped or stress-free) cylindrical surface with subwavelength corrugations, which resides on a thin elastic plate, under excitation by an incident flexural plane wave. Numerical characterization of this corrugated rigid structure shows that it is elastically equivalent to a cylindrical scatterer with dispersive but uniformly negative flexural rigidity. This, indeed, suggests that plasmoniclike elastic materials can be engineered with potential applications in various areas including earthquake sensing and elastic imaging and cloaking.

  8. Near-infrared trapped mode magnetic resonance in an all-dielectric metamaterial.

    PubMed

    Zhang, Jianfa; MacDonald, Kevin F; Zheludev, Nikolay I

    2013-11-04

    Optical responses in conventional metamaterials based on plasmonic metal nanostructures are inevitably accompanied by Joule losses, which obstruct practical applications by limiting resonance quality factors and compromising the efficiency of metamaterial devices. Here we experimentally demonstrate a fully-dielectric metamaterial that exhibits a 'trapped mode' resonance at optical frequencies, founded upon the excitation by incident light of anti-parallel displacement currents in meta-molecules comprising pairs of parallel, geometrically dissimilar dielectric nano-bars. The phenomenon is demonstrated in the near-infrared part of the spectrum using silicon, showing that in principle strong, lossless resonant responses are possible anywhere in the optical spectral range.

  9. Frequency resonances in a two-mode He--Ne/I/sub 2/ laser

    SciTech Connect

    Gonchukov, S.A.; Kireev, S.V.; Protsenko, E.D.

    1984-09-01

    The first results are given of investigations of frequency resonances of a /sup 3/He--/sup 20/Ne//sup 127/I/sub 2/ laser (0.63 ..mu.. wavelength) emitting two modes with parallel polarizations. Investigations were made of the resolution, of the amplitudes of the frequency resonances and their shifts, and of the influence of the temperature on the frequency pedestal. It is shown that the high signal-to-noise ratio makes frequency resonances promising for use in laser spectroscopy.

  10. THz Pyro-Optical Detector Based on LiNbO₃ Whispering Gallery Mode Microdisc Resonator.

    PubMed

    Cosci, Alessandro; Cerminara, Matteo; Conti, Gualtiero Nunzi; Soria, Silvia; Righini, Giancarlo C; Pelli, Stefano

    2017-01-28

    This study analyzes the capabilities of a LiNbO₃ whispering gallery mode microdisc resonator as a potential bolometer detector in the THz range. The resonator is theoretically characterized in the stationary regime by its thermo-optic and thermal coefficients. Considering a Q-factor of 10⁷, a minimum detectable power of 20 μW was evaluated, three orders of magnitude above its noise equivalent power. This value opens up the feasibility of exploiting LiNbO₃ disc resonators as sensitive room-temperature detectors in the THz range.

  11. Vertically-coupled Whispering Gallery Mode Resonator Optical Waveguide, and Methods

    NASA Technical Reports Server (NTRS)

    Matsko, Andrey B. (Inventor); Savchenkov, Anatolly A. (Inventor); Matleki, Lute (Inventor)

    2007-01-01

    A vertically-coupled whispering gallery mode (WGM) resonator optical waveguide, a method of reducing a group velocity of light, and a method of making a waveguide are provided. The vertically-coupled WGM waveguide comprises a cylindrical rod portion having a round cross-section and an outer surface. First and second ring-shaped resonators are formed on the outer surface of the cylindrical rod portion and are spaced from each other along a longitudinal direction of the cylindrical rod. The first and second ringshaped resonators are capable of being coupled to each other by way an evanescent field formed in an interior of the cylindrical rod portion.

  12. A complete dc characterization of a constant-frequency, clamped-mode, series-resonant converter

    NASA Technical Reports Server (NTRS)

    Tsai, Fu-Sheng; Lee, Fred C.

    1988-01-01

    The dc behavior of a clamped-mode series-resonant converter is characterized systematically. Given a circuit operating condition, the converter's mode of operation is determined and various circuit parameters are calculated, such as average inductor current (load current), rms inductor current, peak capacitor voltage, rms switch currents, average diode currents, switch turn-on currents, and switch turn-off currents. Regions of operation are defined, and various circuit characteristics are derived to facilitate the converter design.

  13. Acoustic mode driven by fast electrons in TJ-II Electron Cyclotron Resonance plasmas

    NASA Astrophysics Data System (ADS)

    Sun, B. J.; Ochando, M. A.; López-Bruna, D.

    2016-08-01

    Intense harmonic oscillations in radiation signals (δ I/I∼ 5{%}) are commonly observed during Electron Cyclotron Resonance (ECR) heating in TJ-II stellarator plasmas at low line-averaged electron density, 0.15 < \\bar{n}e < 0.6 ×1019 \\text{m}-3 . The frequency agrees with acoustic modes. The poloidal modal structure is compatible with Geodesic Acoustic Modes (GAM) but an n \

  14. MRI Mode Programming for Safe Magnetic Resonance Imaging in Patients With a Magnetic Resonance Conditional Cardiac Device.

    PubMed

    Nakai, Toshiko; Kurokawa, Sayaka; Ikeya, Yukitoshi; Iso, Kazuki; Takahashi, Keiko; Sasaki, Naoko; Ashino, Sonoko; Okubo, Kimie; Okumura, Yasuo; Kunimoto, Satoshi; Watanabe, Ichiro; Hirayama, Atsushi

    2016-01-01

    Although diagnostically indispensable, magnetic resonance imaging (MRI) has been, until recently, contraindicated in patients with an implantable cardiac device. MR conditional cardiac devices are now widely used, but the mode programming needed for safe MRI has yet to be established. We reviewed the details of 41 MRI examinations of patients with a MR conditional device. There were no associated adverse events. However, in 3 cases, paced beats competed with the patient's own beats during the MRI examination. We describe 2 of the 3 specific cases because they illustrate these potentially risky situations: a case in which the intrinsic heart rate increased and another in which atrial fibrillation occurred. Safe MRI in patients with an MR conditional device necessitates detailed MRI mode programming. The MRI pacing mode should be carefully and individually selected.

  15. High-Q AlN Contour Mode Resonators with Unattached, Voltage-Actuated Electrodes

    NASA Astrophysics Data System (ADS)

    Schneider, Robert Anthony

    High-Q narrowband filters at ultra-high frequencies hold promise for reducing noise and suppressing interferers in wireless transceivers, yet research efforts confront a daunting challenge. So far, no existing resonator technology can provide the simultaneous high-Q, high electromechanical coupling ( k2eff), frequency tunability, low motional resistance (Rx), stopband rejection, self-switchability, frequency accuracy, and power handling desired to select individual channels or small portions of a band over a wide RF range. Indeed, each technology provides only a subset of the desired properties. Recently introduced "capacitive-piezoelectric" resonators, i.e., piezoelectric resonators with non-contacting transduction electrodes, known for achieving very good Q's, have recently emerged (in the early 2010's) as a contender among existing technologies to address the needs of RF narrowband selection. Several reports of such devices, made from aluminum nitride (AlN), have demonstrated improved Q's over attached electrode counterparts at frequencies up to 1.2 GHz, albeit with reduced transduction efficiency due to the added capacitive gaps. Fabrication challenges, while still allowing for a glimpse of the promise of this technology, have, until now, hindered attempts at more complex devices than just simple resonators with improved Q's. This thesis project demonstrates several key improvements to capacitive-piezo technology, which, taken together, further bolster its case for deployment for frequency control applications. (Abstract shortened by ProQuest.).

  16. Emergence of resonant mode-locking via delayed feedback in quantum dot semiconductor lasers.

    PubMed

    Tykalewicz, B; Goulding, D; Hegarty, S P; Huyet, G; Erneux, T; Kelleher, B; Viktorov, E A

    2016-02-22

    With conventional semiconductor lasers undergoing external optical feedback, a chaotic output is typically observed even for moderate levels of the feedback strength. In this paper we examine single mode quantum dot lasers under strong optical feedback conditions and show that an entirely new dynamical regime is found consisting of spontaneous mode-locking via a resonance between the relaxation oscillation frequency and the external cavity repetition rate. Experimental observations are supported by detailed numerical simulations of rate equations appropriate for this laser type. The phenomenon constitutes an entirely new mode-locking mechanism in semiconductor lasers.

  17. Off-resonance coupling between a cavity mode and an ensemble of driven spins

    NASA Astrophysics Data System (ADS)

    Wang, Hui; Masis, Sergei; Levi, Roei; Shtempluk, Oleg; Buks, Eyal

    2017-05-01

    We study the interaction between a superconducting cavity and a spin ensemble. The response of a cavity mode is monitored while simultaneously the spins are driven at a frequency close to their Larmor frequency, which is tuned to a value much higher than the cavity resonance. We experimentally find that the effective damping rate of the cavity mode is shifted by the driven spins. The measured shift in the damping rate is attributed to the retarded response of the cavity mode to the driven spins. The experimental results are compared with theoretical predictions and fair agreement is found.

  18. Acoustic fatigue life prediction for nonlinear structures with multiple resonant modes

    NASA Technical Reports Server (NTRS)

    Miles, R. N.

    1992-01-01

    This report documents an effort to develop practical and accurate methods for estimating the fatigue lives of complex aerospace structures subjected to intense random excitations. The emphasis of the current program is to construct analytical schemes for performing fatigue life estimates for structures that exhibit nonlinear vibration behavior and that have numerous resonant modes contributing to the response.

  19. Aberration influence and active compensation on laser mode properties for asymmetric folded resonators

    NASA Astrophysics Data System (ADS)

    Zhang, Xiang; Hu, Zhiqiu; Yang, Wentao; Su, Likun

    2017-09-01

    We demonstrate the influence on mode features with introducing typical intracavity perturbation and results of aberrated wavefront compensation in a folded-type unstable resonator used in high energy lasers. The mode properties and aberration coefficient with intracavity misalignment are achieved by iterative calculation and Zernike polynomial fitting. Experimental results for the relation of intracavity maladjustment and mode characteristics are further obtained in terms of S-H detection and model wavefront reconstruction. It indicates that intracavity phase perturbation has significant influence on out coupling beam properties, and the uniform and symmetry of the mode is rapidly disrupted even by a slight misalignment of the resonator mirrors. Meanwhile, the far-field beam patterns will obviously degrade with increasing the distance between the convex mirror and the phase perturbation position even if the equivalent disturbation is inputted into such the resonator. The closed-loop device for compensating intracavity low order aberration is successfully fabricated. Moreover, Zernike defocus aberration is also effectively controlled by precisely adjusting resonator length, and the beam quality is noticeably improved.

  20. Acoustic fatigue life prediction for nonlinear structures with multiple resonant modes

    NASA Astrophysics Data System (ADS)

    Miles, R. N.

    1992-03-01

    This report documents an effort to develop practical and accurate methods for estimating the fatigue lives of complex aerospace structures subjected to intense random excitations. The emphasis of the current program is to construct analytical schemes for performing fatigue life estimates for structures that exhibit nonlinear vibration behavior and that have numerous resonant modes contributing to the response.

  1. Traveling-Wave Maser for 32 GHz

    NASA Technical Reports Server (NTRS)

    Shell, James; Clauss, Robert

    2009-01-01

    The figure depicts a traveling-wave ruby maser that has been designed (though not yet implemented in hardware) to serve as a low-noise amplifier for reception of weak radio signals in the frequency band of 31.8 to 32.3 GHz. The design offers significant improvements over previous designs of 32-GHz traveling-wave masers. In addition, relative to prior designs of 32-GHz amplifiers based on high-electron-mobility transistors, this design affords higher immunity to radio-frequency interference and lower equivalent input noise temperature. In addition to the basic frequency-band and low-noise requirements, the initial design problem included a requirement for capability of operation in a closed-cycle helium refrigerator at a temperature .4 K and a requirement that the design be mechanically simplified, relative to prior designs, in order to minimize the cost of fabrication and assembly. Previous attempts to build 32- GHz traveling-wave masers involved the use of metallic slow-wave structures comprising coupled transverse electromagnetic (TEM)-mode resonators that were subject to very tight tolerances and, hence, were expensive to fabricate and assemble. Impedance matching for coupling signals into and out of these earlier masers was very difficult. A key feature of the design is a slow-wave structure, the metallic portions of which would be mechanically relatively simple in that, unlike in prior slow-wave structures, there would be no internal metal steps, irises, or posts. The metallic portions of the slow-wave structure would consist only of two rectangular metal waveguide arms. The arms would contain sections filled with the active material (ruby) alternating with evanescent-wave sections. This structure would be transparent in both the signal-frequency band (the aforementioned range of 31.8 to 32.3 GHz) and the pump-frequency band (65.75 to 66.75 GHz), and would impose large slowing factors in both frequency bands. Resonant ferrite isolators would be placed in the

  2. Theory of beat-resonant coupling of electrostatic modes. [in nonuniform Vlasov plasma

    NASA Technical Reports Server (NTRS)

    Crawford, John David; Kaufman, Allan N.; Oberman, Carl; Johnston, Shayne

    1986-01-01

    A general expression is derived for the beat-resonant coupling electrostatic modes in a Vlasov plasma. The result for the coupling of two modes has a simple structure: the appropriate momentum gradient of the equilibrium particle distribution is weighted by a positive coupling coefficient and averaged over the resonance surface in momentum space. The contributions of all the resonance surfaces are then summed. This basic structure had been previously exhibited only for specific homogeneous plasma models. The present theory, which unifies and greatly simplifies these individual treatments, is based on a variational formulation of the Vlasov-Poisson equations. Using Lie transforms, the variational principle is reexpressed in oscillation-center variables, and then the nonlinear wave dynamics are obtained from the independent variations of the wave phase and the wave amplitude. The power of the method is then applied to a strongly magnetized, strongly inhomogeneous, non-neutral plasma model.

  3. Role of Resonance Modes on Terahertz Metamaterials based Thin Film Sensors.

    PubMed

    Islam, Maidul; Rao, S Jagan Mohan; Kumar, Gagan; Pal, Bishnu P; Roy Chowdhury, Dibakar

    2017-08-04

    We investigate thin film sensing capabilities of a terahertz (THz) metamaterial, which comprises of an array of single split gap ring resonators (SRRs). The top surface of the proposed metamaterial is covered with a thin layer of analyte in order to examine various sensing parameters. The sensitivity and corresponding figure of merit (FoM) of the odd and even resonant modes are analyzed with respect to different thicknesses of the coated analyte film. The sensing parameters of different resonance modes are elaborated and explained with appropriate physical explanations. We have also employed a semi-analytical transmission line model in order to validate our numerically simulated observations. Such study should be very useful for the development of metamaterials based sensing devices, bio-sensors etc in near future.

  4. Dual-mode thin film bulk acoustic wave resonators for parallel sensing of temperature and mass loading.

    PubMed

    García-Gancedo, L; Pedrós, J; Zhao, X B; Ashley, G M; Flewitt, A J; Milne, W I; Ford, C J B; Lu, J R; Luo, J K

    2012-01-01

    Thin film bulk acoustic wave resonator (FBAR) devices supporting simultaneously multiple resonance modes have been designed for gravimetric sensing. The mechanism for dual-mode generation within a single device has been discussed, and theoretical calculations based on finite element analysis allowed the fabrication of FBARs whose resonance modes have opposite reactions to temperature changes; one of the modes exhibiting a positive frequency shift for a rise of temperature whilst the other mode exhibits a negative shift. Both modes exhibit negative frequency shift for a mass load and hence by monitoring simultaneously both modes it is possible to distinguish whether a change in the resonance frequency is due to a mass load or temperature variation (or a combination of both), avoiding false positive/negative responses in gravimetric sensing without the need of additional reference devices or complex electronics.

  5. Enhanced visibility of two-mode thermal squeezed states via degenerate parametric amplification and resonance

    NASA Astrophysics Data System (ADS)

    Mahboob, I.; Okamoto, H.; Yamaguchi, H.

    2016-08-01

    Two-mode squeezed states, generated via non-degenerate parametric down-conversion, are invariably revealed via their entangled vacuum or correlated thermal fluctuations. Here, two-mode thermal squeezed states, generated in an electromechanical system, are made bright by means of degenerate parametric amplification of their constituent modes to the point where they are almost perfect, even when seeded from low intensity non-degenerate parametric down-conversion. More dramatically, activating the degenerate parametric resonances of the underlying modes yields perfect correlations which can be resolved via the coordinated switching of their phase bi-stable vibrations, without recourse to monitoring their thermal fluctuations. This ability to enhance the two-mode squeezed states and to decipher them without needing to observe their intrinsic noise is supported by both analytical and numerical modelling and it suggests that the technical constraints to making this phenomenon more widely available can be dramatically relaxed.

  6. Simulations of peeling-ballooning modes with electron cyclotron resonance heating

    SciTech Connect

    Huang, J.; Tang, C. J.; Chen, S. Y.

    2016-05-15

    The effects of the deposited power and deposited position of Electron Cyclotron Resonance Heating (ECRH) on Peeling-Ballooning (P-B) modes are simulated using BOUT++ code in this paper. The simulation results show that as the deposited position moves from the top to the bottom of the pedestal, the edge localized mode (ELM) size decreases first and then increases, finally decreases again. For ECRH with different deposited power, the effects on P-B modes are similar if they have the same peak value of the power deposition profile. These results show that the effects of ECRH on P-B modes are primarily determined by the change in pressure profile caused by ECRH. As long as ECRH can lead to large enough change in pressure profile, ECRH can efficiently affect the dynamics of P-B modes.

  7. A new boundary integral approach to the determination of the resonant modes of arbitrary shaped cavities

    SciTech Connect

    Arcioni, P.; Bressan, M.; Perregrini, L.

    1995-08-01

    Computer codes for the electromagnetic analysis of arbitrarily shaped cavities are very important for many applications, in particular for the design of interaction structures for particle accelerators. The design of accelerating cavities results in complicated shapes, that are obtained carrying on repeated analyses to optimize a number of parameters, such as Q-factors, beam coupling impedances, higher-order-mode spectrum, and so on. The interest in the calculation of many normalized modes derives also from the important role they play in the eigenvector expansion of the electromagnetic field in a closed region. The authors present an efficient algorithm to determine the resonant frequencies and the normalized modal fields of arbitrarily shaped cavity resonators filled with a lossless, isotropic, and homogeneous medium. The algorithm is based on the boundary integral method (BIM). The unknown current flowing on the cavity wall is considered inside a spherical resonator, rather than in free-space, as it is usual in the standard BIM. The electric field is expressed using the Green`s function of the spherical resonator, approximated by a real rational function of the frequency. Consequently, the discretized problem can be cast into the form of a real matrix linear eigenvalue problem, whose eigenvalues and eigenvectors yield the resonant frequencies and the associated modal currents. Since the algorithm does not require any frequency-by-frequency recalculation of the system matrices, computing time is much shorter than in the standard BIM, especially when many resonances must be found.

  8. Superconducting magnet performance for 28 GHz electron cyclotron resonance ion source developed at the Korea Basic Science Institute

    SciTech Connect

    Park, Jin Yong; Choi, Seyong; Lee, Byoung-Seob; Yoon, Jang-Hee; Ok, Jung-Woo; Shin, Chang Seouk; Won, Mi-Sook; Kim, Byoung Chul; Ahn, Jung Keun

    2014-02-15

    A superconducting magnet for use in an electron cyclotron resonance ion source was developed at the Korea Basic Science Institute. The superconducting magnet is comprised of three solenoids and a hexapole magnet. According to the design value, the solenoid magnets can generate a mirror field, resulting in axial magnetic fields of 3.6 T at the injection area and 2.2 T at the extraction region. A radial field strength of 2.1 T can also be achieved by hexapole magnet on the plasma chamber wall. NbTi superconducting wire was used in the winding process following appropriate techniques for magnet structure. The final assembly of the each magnet involved it being vertically inserted into the cryostat to cool down the temperature using liquid helium. The performance of each solenoid and hexapole magnet was separately verified experimentally. The construction of the superconducting coil, the entire magnet assembly for performance testing and experimental results are reported herein.

  9. Superconducting magnet performance for 28 GHz electron cyclotron resonance ion source developed at the Korea Basic Science Institute.

    PubMed

    Park, Jin Yong; Choi, Seyong; Lee, Byoung-Seob; Yoon, Jang-Hee; Ok, Jung-Woo; Kim, Byoung Chul; Shin, Chang Seouk; Ahn, Jung Keun; Won, Mi-Sook

    2014-02-01

    A superconducting magnet for use in an electron cyclotron resonance ion source was developed at the Korea Basic Science Institute. The superconducting magnet is comprised of three solenoids and a hexapole magnet. According to the design value, the solenoid magnets can generate a mirror field, resulting in axial magnetic fields of 3.6 T at the injection area and 2.2 T at the extraction region. A radial field strength of 2.1 T can also be achieved by hexapole magnet on the plasma chamber wall. NbTi superconducting wire was used in the winding process following appropriate techniques for magnet structure. The final assembly of the each magnet involved it being vertically inserted into the cryostat to cool down the temperature using liquid helium. The performance of each solenoid and hexapole magnet was separately verified experimentally. The construction of the superconducting coil, the entire magnet assembly for performance testing and experimental results are reported herein.

  10. Measurement and reliability issues in resonant mode cantilever for bio-sensing application in fluid medium

    NASA Astrophysics Data System (ADS)

    Kathel, G.; Shajahan, M. S.; Bhadra, P.; Prabhakar, A.; Chadha, A.; Bhattacharya, E.

    2016-09-01

    Cantilevers immersed in liquid experience viscous damping and hydrodynamic loading. We report on the use of such cantilevers, operating in the dynamic mode with, (i) frequency sweeping and (ii) phase locked loop methods. The solution to reliability issues such as random drift in the resonant peak values, and interference of spurious modes in the resonance frequency spectrum, are explained based on the actuation signal provided and laser spot size. The laser beam spot size and its position on the cantilever were found to have an important role, on the output signal and resonance frequency. We describe a method to distinguish the normal modes from the spurious modes for a cantilever. Uncertainties in the measurements define the lower limit of mass detection (m min). The minimum detection limits of the two measurement methods are investigated by measuring salt adsorption from phosphate buffer solution, as an example, a mass of 14 pg was measured using the 14th transverse mode of a 500~μ m  ×  100 μm  ×  1 μm silicon cantilever. The optimized measurement was used to study the interaction between antibody and antigen.

  11. Investigation of higher spanwise Helmholtz resonance modes in slender covered cavities.

    PubMed

    de Jong, A T; Bijl, H

    2010-10-01

    Cavity aeroacoustic noise is relevant for aerospace and automotive industries and widely investigated since the 1950s. Most investigations so far consider cavities where opening length and width are of similar scale. The present investigation focuses on a less investigated setup, namely cavities that resemble the door gaps of automobiles. These cavities are both slender (width much greater than length or depth) and partially covered. Furthermore they are under influence of a low Mach number flow with a relatively thick boundary layer. Under certain conditions, these gaps can produce tonal noise. The present investigation attempts to reveal the aeroacoustic mechanism of this tonal noise for higher resonance modes. Experiments have been conducted on a simplified geometry, where unsteady internal pressures have been measured at different spanwise locations. With increasing velocity, several resonance modes occur. In order to obtain higher mode shapes, the cavity acoustic response is simulated and compared with experiment. Using the frequency-filtered simulation pressure field, the higher modes shapes are retrieved. The mode shapes can be interpreted as the slender cavity self-organizing into separate Helmholtz resonators that interact with each other. Based on this, an analytical model is derived that shows good agreement with the simulations and experimental results.

  12. Resonant magnetic exciton mode in the heavy-fermion antiferromagnet CeB₆.

    PubMed

    Friemel, G; Li, Yuan; Dukhnenko, A V; Shitsevalova, N Y; Sluchanko, N E; Ivanov, A; Filipov, V B; Keimer, B; Inosov, D S

    2012-05-15

    Resonant magnetic excitations are recognised as hallmarks of unconventional superconductivity in copper oxides, iron pnictides and heavy-fermion compounds. Model calculations have related these modes to the microscopic properties of the pair wave function, but the mechanisms of their formation are still debated. Here we report the discovery of a similar resonant mode in the non-superconducting antiferromagnetic heavy-fermion metal CeB(6). Unlike conventional magnons, the mode is non-dispersive and is sharply peaked around a wave vector separate from those characterising the antiferromagnetic order. It is likely associated with a co-existing order parameter of the unusual antiferro-quadrupolar phase of CeB(6), which has long remained hidden to neutron-scattering probes. The mode energy increases continuously below the onset temperature for antiferromagnetism, in parallel to the opening of a nearly isotropic spin gap throughout the Brillouin zone. These attributes are similar to those of the resonant modes in unconventional superconductors. This unexpected commonality between the two disparate ground states indicates the dominance of itinerant spin dynamics in the ordered low-temperature phases of CeB(6) and throws new light on the interplay between antiferromagnetism, superconductivity and 'hidden' order parameters in correlated-electron materials.

  13. Ultrasonic attenuation in amorphous silicon at 50 and 100 GHz

    NASA Astrophysics Data System (ADS)

    Hondongwa, D. B.; Daly, B. C.; Norris, T. B.; Yan, B.; Yang, J.; Guha, S.

    2011-03-01

    We have measured the attenuation of longitudinal acoustic waves in a series of amorphous and nanocrystalline silicon films using picosecond ultrasonics. The films were grown using a modified very high frequency glow discharge method on steel substrates. The deposition conditions were similar to that used in the fabrication of high-efficiency solar cells. The film thicknesses were varied so we could distinguish between interface losses and intrinsic losses within the silicon films. We determine the attenuation of amorphous Si to be 780 ± 160 cm-1 at 100 GHz and 340 ± 120 cm-1 at 50 GHz, values that are lower than those predicted by theories based on anharmonic interactions of the sound wave with localized phonons or extended resonant modes. We determine the attenuation of nanocrystalline Si at 50 GHz to be nearly an order of magnitude higher than amorphous Si (2600 ± 660 cm-1) and compare that value to a simple Rayleigh scattering prediction.

  14. Broad area lasers with folded-resonator geometry for integrated transverse mode selection

    NASA Astrophysics Data System (ADS)

    Hoffmann, Dirk; Huthmacher, Klaus; Doering, Christoph; Fouckhardt, Henning

    2011-02-01

    AlGaInAsSb-based broad area lasers (BALs) with a monolithically integrated Fourier-optical 4f set-up in a folded-resonator geometry are realized. The two resonator branches - each one d = 0.825 mm long - are connected through a dry-etched cylindrical total-internal-reflection (TIR) mirror acting as a Fourier-transform element. Transverse mode selection (TMS) is achieved by monolithically integrated spatial-frequency filters positioned in the back focal plane of the mirror (i.e. in the Fourier-transform plane). The whole resonator is gain section (active medium) as well as part of the TMS 4f set-up at the same time. The integration of TMS within the active BAL chip is shown to be successful. All employed BAL/TMS type-II heterostructure lasers are MBE-grown on GaSb substrates, designed for an emission wavelength in the mid-infrared around 2 μm. Different laser samples without any filter elements (no-TMS) and with filters for the selection of the fundamental transverse mode (#0; TMS0) are prepared and characterized. Just for a proof of principle also samples for the selection of higher order transverse modes, here exemplarily mode #6 (TMS6) and #8 (TMS8), have been processed and investigated. The free spectral range between the longitudinal modes is found to be around 0.33 nm corresponding to the BAL's total-resonator length 2d = 1.65 mm (with an effective refractive index neff ~ 3.8). This result strongly emphasizes that both resonator branches act together as one entity.

  15. Internal Mode Structure of Resonant Field Amplification in DIII-D

    NASA Astrophysics Data System (ADS)

    Lanctot, M. J.; Navratil, G.; Reimerdes, H.; Bogatu, I. N.; in, Y.; Chu, M. S.; Garofalo, A. M.; Jackson, G. L.; La Haye, R. J.; Strait, E. J.; Turnbull, A. D.; Liu, Y. Q.; Okabayashi, M.; Solomon, W. M.

    2008-11-01

    The sensitivity of high-β plasmas to error fields is caused by a paramagnetic plasma response to error fields with a topology that is resonant with the structure of weakly-damped resistive wall modes (RWM), a phenomenon referred to as resonant field amplification (RFA) [1]. The RFA has been driven in DIII-D H-mode plasmas by applying slowly-rotating, low-n magnetic fields with a set of 12 coils located inside the vacuum vessel. Measurements of the RFA mode structure have been obtained using a pair of soft x-ray photodiode cameras. A virtual diagnostic has been developed to compare the measurements to the eigenfunctions for the free boundary external kink and the RWM, which were calculated using the stability codes GATO and MARS-F. Details of the analysis will be presented. 6pt [1] A.H. Boozer, Phys. Rev. Lett. 86, 5059 (2001).

  16. BICEP2/Keck Array V: Measurements of B-mode Polarization at Degree Angular Scales and 150 GHz by the Keck Array

    NASA Astrophysics Data System (ADS)

    BICEP2 and Keck Array Collaborations; Ade, P. A. R.; Ahmed, Z.; Aikin, R. W.; Alexander, K. D.; Barkats, D.; Benton, S. J.; Bischoff, C. A.; Bock, J. J.; Brevik, J. A.; Buder, I.; Bullock, E.; Buza, V.; Connors, J.; Crill, B. P.; Dowell, C. D.; Dvorkin, C.; Duband, L.; Filippini, J. P.; Fliescher, S.; Golwala, S. R.; Halpern, M.; Harrison, S.; Hasselfield, M.; Hildebrandt, S. R.; Hilton, G. C.; Hristov, V. V.; Hui, H.; Irwin, K. D.; Karkare, K. S.; Kaufman, J. P.; Keating, B. G.; Kefeli, S.; Kernasovskiy, S. A.; Kovac, J. M.; Kuo, C. L.; Leitch, E. M.; Lueker, M.; Mason, P.; Megerian, K. G.; Netterfield, C. B.; Nguyen, H. T.; O'Brient, R.; Ogburn, R. W., IV; Orlando, A.; Pryke, C.; Reintsema, C. D.; Richter, S.; Schwarz, R.; Sheehy, C. D.; Staniszewski, Z. K.; Sudiwala, R. V.; Teply, G. P.; Thompson, K. L.; Tolan, J. E.; Turner, A. D.; Vieregg, A. G.; Weber, A. C.; Willmert, J.; Wong, C. L.; Yoon, K. W.

    2015-10-01

    The Keck Array is a system of cosmic microwave background polarimeters, each similar to the Bicep2 experiment. In this paper we report results from the 2012 to 2013 observing seasons, during which the Keck Array consisted of five receivers all operating in the same (150 GHz) frequency band and observing field as Bicep2. We again find an excess of B-mode power over the lensed-ΛCDM expectation of >5σ in the range 30 < ℓ < 150 and confirm that this is not due to systematics using jackknife tests and simulations based on detailed calibration measurements. In map difference and spectral difference tests these new data are shown to be consistent with Bicep2. Finally, we combine the maps from the two experiments to produce final Q and U maps which have a depth of 57 nK deg (3.4 μK arcmin) over an effective area of 400 deg2 for an equivalent survey weight of 250,000 μK-2. The final BB band powers have noise uncertainty a factor of 2.3 times better than the previous results, and a significance of detection of excess power of >6σ.

  17. BICEP2 / Keck Array V: Measurements of B-mode polarization at degree angular scales and 150 GHz by the Keck Array

    DOE PAGES

    Ade, P. A. R.; Ahmed, Z.; Aikin, R. W.; ...

    2015-09-29

    Here, the Keck Array is a system of cosmic microwave background polarimeters, each similar to the Bicep2 experiment. In this paper we report results from the 2012 to 2013 observing seasons, during which the Keck Array consisted of five receivers all operating in the same (150 GHz) frequency band and observing field as Bicep2. We again find an excess of B-mode power over the lensed-ΛCDM expectation of >5σ in the range 30 < ℓ < 150 and confirm that this is not due to systematics using jackknife tests and simulations based on detailed calibration measurements. In map difference and spectralmore » difference tests these new data are shown to be consistent with Bicep2. Finally, we combine the maps from the two experiments to produce final Q and U maps which have a depth of 57 nK deg (3.4 μK arcmin) over an effective area of 400 deg2 for an equivalent survey weight of 250,000 μK–2. The final BB band powers have noise uncertainty a factor of 2.3 times better than the previous results, and a significance of detection of excess power of >6σ.« less

  18. BICEP2/KECK ARRAY V: MEASUREMENTS OF B-MODE POLARIZATION AT DEGREE ANGULAR SCALES AND 150 GHz BY THE KECK ARRAY

    SciTech Connect

    Ade, P. A. R.; Ahmed, Z.; Aikin, R. W.; Bock, J. J.; Brevik, J. A.; Crill, B. P.; Filippini, J. P.; Golwala, S. R.; Alexander, K. D.; Bischoff, C. A.; Buder, I.; Buza, V.; Connors, J.; Dvorkin, C.; Barkats, D.; Benton, S. J.; Bullock, E.; Dowell, C. D.; Duband, L.; Fliescher, S.; Collaboration: Keck Array and Bicep2 Collaborations; and others

    2015-10-01

    The Keck Array is a system of cosmic microwave background polarimeters, each similar to the Bicep2 experiment. In this paper we report results from the 2012 to 2013 observing seasons, during which the Keck Array consisted of five receivers all operating in the same (150 GHz) frequency band and observing field as Bicep2. We again find an excess of B-mode power over the lensed-ΛCDM expectation of >5σ in the range 30 < ℓ < 150 and confirm that this is not due to systematics using jackknife tests and simulations based on detailed calibration measurements. In map difference and spectral difference tests these new data are shown to be consistent with Bicep2. Finally, we combine the maps from the two experiments to produce final Q and U maps which have a depth of 57 nK deg (3.4 μK arcmin) over an effective area of 400 deg{sup 2} for an equivalent survey weight of 250,000 μK{sup −2}. The final BB band powers have noise uncertainty a factor of 2.3 times better than the previous results, and a significance of detection of excess power of >6σ.

  19. Temperature coefficient of frequency modeling for CMOS-MEMS bulk mode composite resonators.

    PubMed

    Wang, Siping; Chen, Wen-Chien; Bahr, Bichoy; Fang, Weileun; Li, Sheng-Shian; Weinstein, Dana

    2015-06-01

    CMOS-MEMS resonators, which are promising building blocks for achieving monolithic integration of MEMS structure, can be used for timing and filtering applications, and control circuitry. SiO2 has been used to make MEMS resonators with quality factor Q > 10(4), but temperature instability remains a major challenge. In this paper, a design that uses an embedded metal block for temperature compensation is proposed and shows sub-ppm temperature stability (-0.21 ppm/K). A comprehensive analytical model is derived and applied to analyze and optimize the temperature coefficient of frequency (TCF) of the CMOS-MEMS composite material resonator. Comparison with finite element method simulation demonstrates good accuracy. The model can also be applied to predict and analyze the TCF of MEMS resonators with arbitrary mode shape, and its integration with simulation packages enables interactive and efficient design process.

  20. Nonlinear mode coupling and resonant excitations in two-component Bose-Einstein condensates.

    PubMed

    Xue, Ju-Kui; Li, Guan-Qiang; Zhang, Ai-Xia; Peng, Ping

    2008-01-01

    Nonlinear excitations in two-component Bose-Einstein condensates (BECs) described by two coupled Gross-Pitaevskii equations are investigated analytically and numerically. The beating phenomenon, the higher-harmonic generation, and the mixing of the excited modes are revealed by both variational approximation and numerical method. The strong excitations induced by the parametric resonance are also studied by time-periodic modulation for the intercomponent interaction. The resonance conditions in terms of the modulation frequency and the strength of intercomponent interaction are obtained analytically, which are confirmed by numerical method. Direct numerical simulations show that, when the resonance takes place, periodic phase separation and multisoliton configurations (including soliton trains, soliton pairs, and multidomain walls) can be excited. In particular, we demonstrate a method for formation of multisoliton configurations through parametric resonance in two-component BECs.

  1. Miniaturized Dual-Band Bandpass Filter Using Embedded Dual-Mode Resonator with Controllable Bandwidths

    NASA Astrophysics Data System (ADS)

    Zhu, Chuanming; Xu, Jin; Kang, Wei; Hu, Zhenxin; Wu, Wen

    2016-09-01

    In this paper, a miniaturized dual-band bandpass filter (DB-BPF) using embedded dual-mode resonator (DMR) with controllable bandwidths is proposed. Two passbands are generated by two sets of resonators operating at two different frequencies. One set of resonators is utilized not only as the resonant elements that yield the lower passband, but also as the feeding structures with source-load coupling to excite the other to produce the upper passband. Sufficient degrees of freedom are achieved to control the center frequencies and bandwidths of two passbands. Moreover, multiple transmission zeros (TZs) are created to improve the passband selectivity of the filter. The design of the filter has been demonstrated by the measurement. The filter features not only miniaturized circuit sizes, low insertion loss, independently controllable central frequencies, but also controllable bandwidths and TZs.

  2. Guided mode resonance with extremely high Q-factors in terahertz metamaterials

    NASA Astrophysics Data System (ADS)

    Chen, Hang; Liu, Jianjun; Hong, Zhi

    2017-01-01

    We proposed and demonstrated that guided mode resonance (GMR) response with extremely high quality factor can be achieved in a planar terahertz metamaterial (MM) by rotating split ring resonators (SRRs) or moving the gaps of SRRs in a two-SRR composed MM. Furthermore, a novel extremely sharp asymmetric Fano resonance or electromagnetically induced transparency (EIT) like spectral response can be easily realized by manipulating the coherent interaction between this high Q GMR and the dipole resonance of MM. The new method can be extended to other ranges of the electromagnetic spectrum, and open new horizons for the design of ultra-high Q metamaterials for multifunctional applications, such as ultra-sensitive sensors, narrowband filters, or slow light based devices.

  3. Self-similar pulse-shape mode for femtosecond pulse propagation in medium with resonant nonlinearity

    NASA Astrophysics Data System (ADS)

    Trofimov, Vyacheslav A.; Zakharova, Irina G.; Konar, Swapan

    2014-05-01

    We investigate the mode of laser pulse propagation in homogeneous medium with resonant nonlinearity, at which the shape of pulse is self-similar one along some distance of propagation. We take into account a laser pulse frequency detuning from resonant frequency. Both types of sign for frequency detuning are considered. This results in appearance of a refractive index grating which induced self-action of a laser pulse. I certain cases we develop analytical solution of corresponding nonlinear eigenfunction problem of laser pulse propagation in medium for multi-photon resonance. This solution is confirmed by computer simulation of an eigenfunction problem for Schrödinger equation with considered nonlinearity. Using computer simulation, one shows a validity of existence of such kind of laser pulse propagation in a medium with resonant nonlinear response.

  4. Compact injector with alternating phase focusing-interdigital H-mode linac and superconducting electron cyclotron resonance ion source for heavy ion cancer therapy

    NASA Astrophysics Data System (ADS)

    Hayashizaki, Noriyosu; Hattori, Toshiyuki; Matsui, Shinjiro; Tomizawa, Hiromitsu; Yoshida, Toru; Isokawa, Katsushi; Kitagawa, Atsushi; Muramatsu, Masayuki; Yamada, Satoru; Okamura, Masahiro

    2000-02-01

    We have researched a compact medical accelerator with low investment and running cost for the popularization of heavy ion cancer therapy. As the first step, the compact injector system has been investigated for a Heavy Ion Medical Accelerator in Chiba at National Institute of Radiological Sciences. The proposed new injector system consists of a 6 MeV/u interdigital H-mode (IH) linac of 3.1 m long and a 18 GHz superconducting electron cyclotron resonance (ECR) (SC-ECR) ion source. The IH linac with high power efficiency is appropriate to a medical and industrial injector system. Its beam trajectory was simulated and a prototype has been constructed. The SC-ECR ion source has been designed to realize lightweight and low power consumption and the mirror field distribution was estimated.

  5. High power 303 GHz gyrotron for CTS in LHD

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Y.; Kasa, J.; Saito, T.; Tatematsu, Y.; Kotera, M.; Kubo, S.; Shimozuma, T.; Tanaka, K.; Nishiura, M.

    2015-10-01

    A high-power pulsed gyrotron is under development for 300 GHz-band collective Thomson scattering (CTS) diagnostics in the Large Helical Device (LHD). High-density plasmas in the LHD require a probe wave with power exceeding 100 kW in the sub-terahertz region to obtain sufficient signal intensity and large scattering angles. At the same time, the frequency bandwidth should be less than several tens of megahertz to protect the CTS receiver using a notch filter against stray radiations. Moreover, duty cycles of ~ 10% are desired for the time domain analysis of the CTS spectrum. At present, a 77 GHz gyrotron for electron cyclotron heating is used as a CTS wave source in the LHD. However, the use of such a low-frequency wave suffers from refraction, cutoff and absorption at the electron cyclotron resonance layer. Additionally, the signal detection is severely affected by background noise from electron cyclotron emission. To resolve those problems, high-power gyrotrons in the 300 GHz range have been developed. In this frequency range, avoiding mode competition is critical to realizing high-power and stable oscillation. A moderately over-moded cavity was investigated to isolate a desired mode from neighbouring modes. After successful tests with a prototype tube, the practical one was constructed with a cavity for TE22,2 operation mode, a triode electron gun forming intense laminar electron beams, and an internal mode convertor. We have experimentally confirmed single mode oscillation of the TE22,2 mode at the frequency of 303.3 GHz. The spectrum peak is sufficiently narrow. The output power of 290 kW has been obtained at the moment.

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

    PubMed Central

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

    2017-01-01

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

  7. Fundamental and higher two-dimensional resonance modes of an Alpine valley

    NASA Astrophysics Data System (ADS)

    Ermert, Laura; Poggi, Valerio; Burjánek, Jan; Fäh, Donat

    2014-08-01

    We investigated the sequence of 2-D resonance modes of the sediment fill of Rhône Valley, Southern Swiss Alps, a strongly overdeepened, glacially carved basin with a sediment fill reaching a thickness of up to 900 m. From synchronous array recordings of ambient vibrations at six locations between Martigny and Sion we were able to identify several resonance modes, in particular, previously unmeasured higher modes. Data processing was performed with frequency domain decomposition of the cross-spectral density matrices of the recordings and with time-frequency dependent polarization analysis. 2-D finite element modal analysis was performed to support the interpretation of processing results and to investigate mode shapes at depth. In addition, several models of realistic bedrock geometries and velocity structures could be used to qualitatively assess the sensitivity of mode shape and particle motion dip angle to subsurface properties. The variability of modal characteristics due to subsurface properties makes an interpretation of the modes purely from surface observations challenging. We conclude that while a wealth of information on subsurface structure is contained in the modal characteristics, a careful strategy for their interpretation is needed to retrieve this information.

  8. Tidal interactions of a Maclaurin spheroid - II. Resonant excitation of modes by a close, misaligned orbit

    NASA Astrophysics Data System (ADS)

    Braviner, Harry J.; Ogilvie, Gordon I.

    2015-02-01

    We model a tidally forced star or giant planet as a Maclaurin spheroid, decomposing the motion into the normal modes found by Bryan. We first describe the general prescription for this decomposition and the computation of the tidal power. Although this formalism is very general, forcing due to a companion on a misaligned, circular orbit is used to illustrate the theory. The tidal power is plotted for a variety of orbital radii, misalignment angles, and spheroid rotation rates. Our calculations are carried out including all modes of degree l ≤ 4, and the same degree of gravitational forcing. Remarkably, we find that for close orbits (a/R* ≈ 3) and rotational deformations that are typical of giant planets (e ≈ 0.4) the l = 4 component of the gravitational potential may significantly enhance the dissipation through resonance with surface gravity modes. There are also a large number of resonances with inertial modes, with the tidal power being locally enhanced by up to three orders of magnitude. For very close orbits (a/R* ≈ 3), the contribution to the power from the l = 4 modes is roughly the same magnitude as that due to the l = 3 modes.

  9. Investigation of impinging jet resonant modes using unsteady pressure-sensitive paint measurements

    NASA Astrophysics Data System (ADS)

    Davis, Timothy; Edstrand, Adam; Alvi, Farrukh; Cattafesta, Louis; Yorita, Daisuke; Asai, Keisuke

    2015-05-01

    At given nozzle to plate spacings, the flow field of high-speed impinging jets is known to be characterized by a resonance phenomenon. Large coherent structures that convect downstream and impinge on the surface create strong acoustic waves that interact with the inherently unstable shear layer at the nozzle exit. This feedback mechanism, driven by the coherent structures in the jet shear layer, can either be axisymmetric or helical in nature. Fast-response pressure-sensitive paint (PSP) is applied to the impingement surface to map the unsteady pressure distribution associated with these resonant modes. Phase-averaged results acquired at several kHz are obtained using a flush mounted unsteady pressure transducer on the impingement plate as a reference signal. Tests are conducted on a Mach 1.5 jet at nozzle to plate spacings of . The resulting phase-averaged distribution reveals dramatically different flow fields at the corresponding impingement heights. The existence of a purely axisymmetric mode with a frequency of 6.3 kHz is identified at and is characterized by concentric rings of higher/lower pressure that propagate radially with increasing phase. Two simultaneous modes are observed at with one being a dominant symmetric mode at 7.1 kHz and the second a sub-dominant helical mode at 4.3 kHz. Complimentary phase-conditioned Schlieren images are also obtained visualizing the flow structures associated with each mode and are consistent with the PSP results.

  10. Magnetic-dipolar-mode Fano resonances for microwave spectroscopy of high absorption matter

    NASA Astrophysics Data System (ADS)

    Vaisman, G.; Kamenetskii, E. O.; Shavit, R.

    2015-03-01

    The interaction between high absorption matter and microwave radiated energy is a subject of great importance. In particular, this concerns the microwave spectroscopic characterization of biological liquids. The use of effective testing methods to obtain information about physical properties of different liquids on the molecular level is one of the most important problems in biophysics. However, the standard methods based on microwave resonant techniques are not sufficiently suitable for biological liquids because the resonance peak in a resonator with high-loss liquids is so broad that the material parameters cannot be measured correctly. Although molecular vibrations of biomolecules may have microwave frequencies, it is not thought that such resonant coupling is significant due to their low energy compared with thermal energy and the strongly dampening aqueous environment. This paper presents an innovative microwave sensing technique for different types of lossy materials, including biological liquids. The technique is based on the combination of the microwave perturbation method and the Fano resonance effects observed recently in microwave structures with embedded magnetic-dipolar quantum dots. When the frequency of the magnetic dipolar mode (MDM) resonance is not equal to the cavity resonance frequency, one gets Fano transmission intensity. When the MDM resonance frequency is tuned to the cavity resonance frequency, by a bias magnetic field, one observes a Lorentzian line shape. Use of an extremely narrow Lorentzian peak allows exact probing of the resonant frequency of a cavity loaded by a highly lossy material sample. For different kinds of samples, one has different frequencies of Lorentzian peaks. This presents a picture of precise spectroscopic characterization of high absorption matter in microwaves.

  11. Studies of extraction and transport system for highly charged ion beam of 18 GHz superconducting electron cyclotron resonance ion source at Research Center for Nuclear Physics

    NASA Astrophysics Data System (ADS)

    Yorita, T.; Hatanaka, K.; Fukuda, M.; Ueda, H.; Yasuda, Y.; Morinobu, S.; Tamii, A.; Kamakura, K.

    2014-02-01

    An 18 GHz superconducting electron cyclotron resonance ion source is installed to increase beam currents and to extend the variety of ions especially for highly charged heavy ions which can be accelerated by cyclotrons of Research Center for Nuclear Physics (RCNP), Osaka University. The beam production developments of several ions from B to Xe have been already done [T. Yorita, K. Hatanaka, M. Fukuda, M. Kibayashi, S. Morinobu, H.Okamura, and A. Tamii, Rev. Sci. Instrum. 79, 02A311 (2008) and T. Yorita, K. Hatanaka, M. Fukuda, M. Kibayashi, S. Morinobu, H.Okamura, and A. Tamii, Rev. Sci. Instrum. 81, 02A332 (2010)] and the further studies for those beam extraction and its transport have been done in order to increase the beam current more. The plasma electrode, extraction electrode, and einzel lens are modified. Especially extraction electrode can be applied minus voltage for the beam extraction and it works well to improve the extracted beam current. The extraction voltage dependences of transmission and emittance also have been studied for beam current improvement which is injected into azimuthally varying field cyclotron at RCNP.

  12. Studies of extraction and transport system for highly charged ion beam of 18 GHz superconducting electron cyclotron resonance ion source at Research Center for Nuclear Physics

    SciTech Connect

    Yorita, T. Hatanaka, K.; Fukuda, M.; Ueda, H.; Yasuda, Y.; Morinobu, S.; Tamii, A.; Kamakura, K.

    2014-02-15

    An 18 GHz superconducting electron cyclotron resonance ion source is installed to increase beam currents and to extend the variety of ions especially for highly charged heavy ions which can be accelerated by cyclotrons of Research Center for Nuclear Physics (RCNP), Osaka University. The beam production developments of several ions from B to Xe have been already done [T. Yorita, K. Hatanaka, M. Fukuda, M. Kibayashi, S. Morinobu, H.Okamura, and A. Tamii, Rev. Sci. Instrum. 79, 02A311 (2008) and T. Yorita, K. Hatanaka, M. Fukuda, M. Kibayashi, S. Morinobu, H.Okamura, and A. Tamii, Rev. Sci. Instrum. 81, 02A332 (2010)] and the further studies for those beam extraction and its transport have been done in order to increase the beam current more. The plasma electrode, extraction electrode, and einzel lens are modified. Especially extraction electrode can be applied minus voltage for the beam extraction and it works well to improve the extracted beam current. The extraction voltage dependences of transmission and emittance also have been studied for beam current improvement which is injected into azimuthally varying field cyclotron at RCNP.

  13. Studies of extraction and transport system for highly charged ion beam of 18 GHz superconducting electron cyclotron resonance ion source at Research Center for Nuclear Physics.

    PubMed

    Yorita, T; Hatanaka, K; Fukuda, M; Ueda, H; Yasuda, Y; Morinobu, S; Tamii, A; Kamakura, K

    2014-02-01

    An 18 GHz superconducting electron cyclotron resonance ion source is installed to increase beam currents and to extend the variety of ions especially for highly charged heavy ions which can be accelerated by cyclotrons of Research Center for Nuclear Physics (RCNP), Osaka University. The beam production developments of several ions from B to Xe have been already done [T. Yorita, K. Hatanaka, M. Fukuda, M. Kibayashi, S. Morinobu, H.Okamura, and A. Tamii, Rev. Sci. Instrum. 79, 02A311 (2008) and T. Yorita, K. Hatanaka, M. Fukuda, M. Kibayashi, S. Morinobu, H.Okamura, and A. Tamii, Rev. Sci. Instrum. 81, 02A332 (2010)] and the further studies for those beam extraction and its transport have been done in order to increase the beam current more. The plasma electrode, extraction electrode, and einzel lens are modified. Especially extraction electrode can be applied minus voltage for the beam extraction and it works well to improve the extracted beam current. The extraction voltage dependences of transmission and emittance also have been studied for beam current improvement which is injected into azimuthally varying field cyclotron at RCNP.

  14. Analysis of light propagation in slotted resonator based systems via coupled-mode theory.

    PubMed

    Hiremath, Kirankumar R; Niegemann, Jens; Busch, Kurt

    2011-04-25

    Optical devices with a slot configuration offer the distinct feature of strong electric field confinement in a low refractive index region and are, therefore, of considerable interest in many applications. In this work we investigate light propagation in a waveguide-resonator system where the resonators consist of slotted ring cavities. Owing to the presence of curved material interfaces and the vastly different length scales associated with the sub-wavelength sized slots and the waveguide-resonator coupling regions on the one hand, and the spatial extent of the ring on the other hand, this prototypical system provides significant challenges to both direct numerical solvers and semi-analytical approaches. We address these difficulties by modeling the slot resonators via a frequency-domain spatial Coupled-Mode Theory (CMT) approach, and compare its results with a Discontinuous Galerkin Time-Domain (DGTD) solver that is equipped with curvilinear finite elements. In particular, the CMT model is built on the underlying physical properties of the slotted resonators, and turns out to be quite efficient for analyzing the device characteristics. We also discuss the advantages and limitations of the CMT approach by comparing the results with the numerically exact solutions obtained by the DGTD solver. Besides providing considerable physical insight, the CMT model thus forms a convenient basis for the efficient analysis of more complex systems with slotted resonators such as entire arrays of waveguide-coupled resonators and systems with strongly nonlinear optical properties.

  15. Resonant modes in metal/insulator/metal metamaterials: An analytical study on near-field couplings

    NASA Astrophysics Data System (ADS)

    Ma, Shaojie; Xiao, Shiyi; Zhou, Lei

    2016-01-01

    Metamaterials (MTMs) in a metal/insulator/metal (MIM) configuration have drawn much attention recently, but the resonances in such systems are still not fully understood. Here, we employ a rigorous mode expansion method to analytically study the resonance properties of a model MIM MTM where the top metallic layer consists of an array of metallic stripes. Our analyses, supported by full-wave simulations and microwave experiments, provide a unified platform to understand the resonances in such systems, in which two previously established models are found valid only at certain extreme conditions. In particular, the resonance in such a system undergoes a transition from a vertical Fabry-Pérot type to a transverse type as the spacer thickness shrinks, and the resonance frequency saturates at a particular value in the thin-spacer limit. Finally, we derive a set of analytical formulas to describe how the essential properties (i.e., resonance frequency and quality factor) of the resonance depend on the structural details of the system and verify these analytical relationships by full-wave simulations in MIM systems with complex microstructures.

  16. Ultrahigh Q whispering gallery mode electro-optic resonators on a silicon photonic chip.

    PubMed

    Soltani, Mohammad; Ilchenko, Vladimir; Matsko, Andrey; Savchenkov, Anatoliy; Schlafer, John; Ryan, Colm; Maleki, Lute

    2016-09-15

    Crystalline whispering gallery mode (WGM) electro-optic resonators made of LiNbO3 and LiTaO3 are critical for a wide range of applications in nonlinear and quantum optics, as well as RF photonics, due to their remarkably ultrahigh Q(>108) and large electro-optic coefficient. Achieving efficient coupling of these resonators to planar on-chip optical waveguides is essential for any high-yield and robust practical applications. However, it has been very challenging to demonstrate such coupling while preserving the ultrahigh Q properties of the resonators. Here, we show how the silicon photonic platform can overcome this long-standing challenge. Silicon waveguides with appropriate designs enable efficient and strong coupling to these WGM electro-optic resonators. We discuss various integration architectures of these resonators onto a silicon chip and experimentally demonstrate critical coupling of a planar Si waveguide and an ultrahigh QLiTaO3 resonator (Q∼108). Our results show a promising path for widespread and practical applications of these resonators on a silicon photonic platform.

  17. Bandwidth tunable guided-mode resonance filter using contact coupled gratings at oblique incidence

    NASA Astrophysics Data System (ADS)

    Sang, Tian; Wang, Yueke; Li, Junlang; Zhou, Jianyu; Jiang, Wenwen; Wang, Jicheng; Chen, Guoqing

    2017-01-01

    A novel bandwidth tunable guided-mode resonance filter (GMRF) is proposed based on the contact coupled gratings (CCGs) with the absentee layers at oblique incidence. The design principle of the CCGs with double absentee layers is presented. The lateral shift of the CCGs changes the magnetic field distributions of the waveguide mode in the grating cavity and the surface-confined mode at the cover/grating interface thus facilitates the dynamic control of both the spectral and angular bandwidth of the GMRF. The resonance locations are almost immune to the variation of the lateral shift of the CCGs. The sideband level of the GMRF is almost unaffected by the lateral shift due to the Brewster AR effect. The resonance peak red-shifts quasi-linearly as the incident angle is increased, and the resonance wavelength can be selected by merely tuning the incident angle. The tunable ranges of both the spectral and angular bandwidth can be significantly enhanced by increasing the refractive-index contrast. Low-sideband reflection with controllable bandwidth at 650 nm is designed to demonstrate this concept.

  18. High-contrast power resonances in a linear two-mode He--Ne/I/sub 2/ laser

    SciTech Connect

    Gonchukov, S.; Kireev, S.; Protsenko, E.

    1982-02-01

    The first report is given of the attainment of high-contrast resonances in a linear two-mode /sup 3/He--/sup 22/Ne laser (lambda = 0.63 ..mu..) with an internal /sup 129/I/sub 2/ absorption cell. The maximum contrast ratio of these resonances was 25% and their width was the same as that of similar resonances in the single-mode regime within the measurement error.

  19. Direct and Inverse Techniques of Guided-Mode Resonance Filters Designs

    NASA Technical Reports Server (NTRS)

    Tibuleac, Sorin; Magnusson, Robert; Maldonado, Theresa A.; Zuffada, Cinzia

    1997-01-01

    Guided-mode resonances arise in single or multilayer waveguides where one or more homogeneous layers are replaced by diffraction gratings (Fig. 1.) The diffractive element enables an electromagnetic wave incident on a waveguide grating to be coupled to the waveguide modes supportable by the structure in the absence of the modulation (i.e. the difference between the high and low dielectric constants of the grating) at specific values of the wavelength and incident angle. The periodic modulation of the guide makes the structure leaky, preventing sustained propagation of modes in the waveguide and coupling the waves out into the substrate and cover. As the wavelength is varied around resonance a rapid variation in the intensities of the external propagating waves occurs. By selecting a grating period small enough to eliminate the higher-order propagating waves, an increase in the zero-order intensities up to 100% can result. The pronounced frequency selectivity of guided-mode resonances in dielectric waveguide gratings can be applied to design high-efficiency reflection and transmission filters [1-3].

  20. η collective mode as A1 g Raman resonance in cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Montiel, X.; Kloss, T.; Pépin, C.; Benhabib, S.; Gallais, Y.; Sacuto, A.

    2016-01-01

    We discuss the possible existence of a spin singlet excitation with charge ±2 (η mode) originating the A1 g Raman resonance in cuprate superconductors. This η mode relates the d -wave superconducting singlet pairing channel to a d -wave charge channel. We show that the η boson forms a particle-particle bound state below the 2 Δ threshold of the particle-hole continuum where Δ is the maximum d -wave gap. Within a generalized random phase approximation and Bethe-Salpeter approximation study, we find that this mode has energies similar to the resonance observed with inelastic neutron scattering below the superconducting (SC) coherent peak at 2 Δ in various SC cuprate compounds. We show that it is a very good candidate for the resonance observed in Raman scattering below the 2 Δ peak in the A1 g symmetry. Since the η mode sits in the S =0 channel, it may be observable via Raman, x-ray, or electron energy loss spectroscopy probes.