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51.
A novel approach to generate microwave signals is presented by employing a microfiber ring resonator. The microfiber ring resonator is assembled with a microfiber fabricated by heating and drawing standard single-mode fiber. By cascading microfiber ring resonator acted as a comb filter with a tunable bandpass filter, a wavelength-tunable dual-wavelength single longitudinal-mode laser is achieved. A microwave signal at 15.57 GHz with the linewidth of less than 21 kHz is demonstrated by beating the two wavelengths at a photodetector. 相似文献
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A.M. Basharov G.G. Grigoryan Yu.V. Orlov A.Yu. Shashkov T.G. Yukina N.V. Znamenskiy 《Physics letters. A》2008,372(3):299-304
Experimental data and theoretical model describing superradiance from the LaF3 crystal doped with impurity praseodymium ions are presented in cases of non-resonator and resonator generation. The spiky structure of superradiance is registered and studied. When the crystal is placed inside a resonator, a new channel of energy removal by superradiance related to the resonator mode appears; the old non-resonator channels are preserved, as well. It has been found that the duration of superradiance in each channel decreases, and there arises a modulation independent of the length of resonator. These new peculiarities of superradiance induced by the presence of resonator have been explained on the basis of the developed simple mean-field theory. 相似文献
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A. Waksberg 《International Journal of Infrared and Millimeter Waves》2002,23(4):635-644
Laser resonator losses with output coupling apertures (holes) have been calculated before but in limited ranges. We have extended such calculations, for the benefit of laser designers, using full diffraction theory, to cover the range of the Fresnel Number N up to 100. Here N is defined by a
2/b with a the radius of the two mirrors and b their separation, while is the wavelength of interest. The losses have been examined from the point of view of the field configuration at the mirrors. Such field is modified, in turn, by the size of the aperture.In addition, the results have been compared with a simple linear model. This has been used to derive a simplified expression, in close form, to calculate cavity losses. Although limited in scope, this expression should prove valuable to a laser cavity designer in performing preliminary designs in regions not covered by our detailed calculations. 相似文献
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In air duct noise control, Helmholtz resonators (HR) are considered as narrow band attenuators. For some applications they can be combined in line to form a wide band silencer. This study investigates the role of distance between HR side branch openings on the whole array attenuation. In the case of two resonators with same performance, the optimal distance can be calculated and corresponds to the quarter wave of HR mean frequency. On three or more HR arrays, relationships between resonators parameters and optimal lengths are much more complex. Tuning of such a device requires taking many geometrically coupled parameters into account; hence, design has to be automated. To operate this process, a 2D FEM COMSOL model has been coupled to a global MATLAB optimization solver. Among different types of constructions, arrays made of concentric resonators with transversal openings offers the most efficient and flexible design to optimize distance between openings. This methodology was applied to an existing turbo compressor silencer. Modifying openings and chambers arrangement, using the proposed approach increased the attenuation band by 10%. Another application concerning an air box for a two stroke engine was also investigated. This resulted in a 16L two chambers concept, being replaced by a more compact and more efficient, 8.3L wide band silencer, made of 8 resonators. With this approach it therefore becomes possible to handle available space and required noise attenuation on a required frequency band, all in one process. 相似文献
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Compact In0.67Ga0.33As0.6P0.4/In0.71Ga0.29As0.74P0.26 on InP single ring resonators incorporating 2 × 2 multimode interference (MMI) turning-mirror couplers with cross coupling factor of 0.15 have been demonstrated. The form of race tracks is a 15-degree arc of 260 μm radius joined with a 60-degree arc of 110 μm radius, and finished with another 15-degree arc of 260 μm radius. The MMI turning-mirror coupler of 128 μm in length is used in the single ring resonators, which correspond to free spectral ranges of 82 GHz. A contrast of 4 dB, a finesse of nearly 3 and full-width at half-maximum (FWHM) of 0.24 nm for the drop port have been achieved in this single ring resonator. From the experimental value Tmax/Tmin of 21 dB, the experiment coupling factor coincides with the simulation. 相似文献
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Tkach I Sicoli G Höbartner C Bennati M 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2011,209(2):341-346
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 Δν=350 MHz. To examine its performance, test ESE/PELDOR experiments were performed on a representative biradical system. 相似文献
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A non-linear vibration equation with the consideration of large amplitude, gas damping and excitation is developed to investigate the dynamic performance of a dielectric elastomer (DE)-based microbeam resonator. Approximate analytical solution for the vibration equation is obtained by applying parameterized perturbation method (PPM) and introducing a detuning variable. The analysis exhibits that active tuning of the resonant frequency of the resonator can be achieved through changing an applied electrical voltage. It is observed that increasing amplitude will increase the natural frequency while it will decrease the quality factor of the resonator. In addition, it is found that the initial pre-stretching stress and the ambient pressure can significantly alter the resonant frequency of the resonator. The analysis is envisaged to provide qualitative predictions and guidelines for design and application of DE-based micro resonators with large vibration amplitude. 相似文献