共查询到20条相似文献,搜索用时 15 毫秒
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G. Annino M. Cassettari M. Fittipaldi M. Martinelli 《International Journal of Infrared and Millimeter Waves》2001,22(10):1485-1494
A whispering gallery resonator coupled to a dielectric waveguide is experimentally investigated around 86 GHz using a vectorial network analyzer. The resulting complex response function is compared with a theoretical model, simplified assuming negligible stationary waves; indeed their presence can be effectively compensated by a proper normalization procedure, made possible by a suitable analysis in the complex field. It is demonstrated that the proposed approach well reproduce the experimental results in a wide range of coupling conditions. Moreover, some outcomes of the model concerning the power flowing into the resonator are briefly discussed. 相似文献
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We numerically investigate the behavior of Whispering Gallery Modes (WGMs) in circularly shaped resonators like microdisks, with diameters in the range of optical vacuum wavelengths. The microdisk is embedded in an uniaxial anisotropic dielectric environment. By changing the optical anisotropy, one obtains spectral tunability of the optical modes. The degree of tunability strongly depends on the radial (azimuthal) mode order M (N). As the modes approach each other spectrally, anticrossing is observed, leading to a rearrangement of the optical states. 相似文献
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A. Colligiani P. Guillon I. Longo Prof. M. Martinelli L. Pardi 《Applied magnetic resonance》1992,3(5):827-840
The behaviour of a disc-shaped dielectric resonator (DR) working in the Whispering-Gallery Modes (WGM) when used for X-band ESR experiments has been tested. It has been verified that the WGM in the resonator can be excited by using the microwave bridge of a Bruker spectrometer. The microwave field is well confined in the DR also in the absence of metal shieldings as demonstrated by the high Q values of the detected resonances. A large number of such resonances has been detected from eight up to twelve gigahertz making the DR a very broadband device. ESR spectra of various powder and aqueous samples have been obtained and compared with those of the same samples recorded by using a metal cavity. The relative amplitude of the spectra demonstrated that for aqueous samples the sensitivity of DR is similar to that of the metallic cavity. Further investigations are in progress to enhance the overall performance. 相似文献
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Giuseppe Annino Mario Cassettari Massimo Martinelli 《International Journal of Infrared and Millimeter Waves》2002,23(4):597-615
Several basic properties of homogeneous planar Whispering Gallery dielectric resonators are investigated through a general approach. In particular the values for the minimum and maximum allowed radius, defined by irradiation and dielectric losses, respectively, are obtained in terms of the complex dielectric constant of the involved media. The same approach is employed in the analysis of the limit allowed frequencies of a fixed family of mode, leading to the definition of the ideal frequency band. The role of the transverse mode is then discussed, and the effective frequency band is introduced and determined both in simple disc and circular ring resonators. The extension of the effective band is limited at least by a factor 3, in terms of decades, in comparison to the extension of the ideal one; this limitation, due to the presence of transverse modes, can be overcome using suitable designed nonhomogeneous resonators, as discussed in a following companion paper. 相似文献
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A group representation of radiation propagation in an anisotropic medium is developed. The system of wave equations for electromagnetic potentials, obtained from the Maxwell equations with account for the constitutive equations, has been factorized. It is shown that the linear differential operator of the factorized system is orthogonal in transparent crystals and unitary in gyrotropic ones and is represented through the momentum operator. On the basis of the commutation relations for the components of this operator, the eigenvalue problem has been solved and the expression for the change in the radiant energy in the crystal in the form of spherical waves has been obtained. The dependences of the ray and phase velocities and the polarization vectors of waves on the birefringence anisotropy and gyrotropy as well as on the angular momentum, displacement current, and bound charge determining them have been analyzed. It has been established that in the general case of gyrotropic crystals where the nonreciprocity phenomenon takes place and in magnetoelectrics Maxwell equations are represented in a form similar to the Dirac equations and the electromagnetic radiation is correctly described by means of bispinors and is quantized as fermions. 相似文献
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This paper considers the switching effects on whispering gallery modes in circular dielectric resonators when their material is subject to abrupt time changes in permittivity. Both the transient response and the new steady-state regime are described in detail by means of an analytical approach. 相似文献
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Giuseppe Annino Mario Cassettari Massimo Martinelli 《International Journal of Infrared and Millimeter Waves》2002,23(4):617-634
The basic theory underlying the realization of simple multiple-band non-homogeneous dielectric resonators, whose spectral response is the overlap of single-resonator frequency bands, is developed exploiting a general approach discussed in the previous companion paper. The limit frequencies of the proposed devices, given only by the dielectric properties of the involved materials, can differ in principle by several decades. Experimental confirmations have been obtained on a composite structure built up with teflon and polyethylene; as predicted by the theory, the overall band includes frequencies which range about from 20 GHz to more than 400 GHz, when high frequency resonances are selectively excited. The localization of the higher frequency radiation between the positive steps of the dielectric constant, which is the basic properties of these non-homogeneous resonators, has been experimentally verified by mapping the electromagnetic field intensity. Possible applications of multiple-band Whispering Gallery dielectric resonators are finally outlined. 相似文献
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柱形微腔回音壁激光光谱模式的精确标定 总被引:3,自引:0,他引:3
由柱形微腔中回音壁模式满足的本征值方程,得到确定回音壁模式位置和间距的近似解析公式。以此近似解析公式,首次对直径在215~328 μm间的5个柱形微腔回音壁激光光谱做了模式标定。在用近似解析公式对柱形微腔激光光谱的数值作拟合的计算中,除了回音壁模的径向模式数(l)和角动量模式数(n)外无需其他拟合参数,解析公式的拟合值和实验激光光谱波长值间的偏差小于0.05 nm,拟合结果精确可靠。柱形微腔回音壁激光光谱模式的精确标定在模式的场分布计算以及频移型微腔生物传感器的研究应用中具有重要作用,文章介绍的方法亦可应用于柱形微腔直径和折射率的精密测量。 相似文献
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A. Colligiani I. Longo M. Martinelli M. Lucchesi L. Pardi 《Applied magnetic resonance》1995,9(4):567-579
The behaviour of a disc-shaped dielectric resonator made of sintered alumina and working in the Whispering Gallery Mode (WGM) has been studied in the frequency interval from about 8 up to about 26 GHz. Many equidistant resonances have been detected in this frequency interval each of which being characterized by a satisfactoryQ-value due to the very good self-confinement of the microwave field which is typical of WGM propagation. Particular care has been devoted to the optimization of the coupling between the resonating disc and the microwave source. Examples of ESR spectra obtained on each of the detected resonances are reported which show the variation of the lineshape with the increase of the frequency. The obtained results allow one to foresee that the same dielectric disc can be used for ESR spectroscopy also at frequencies much higher than those up to now exploited. 相似文献
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光学微球腔因其回音壁模式可获得极高的品质因数而受到广泛关注.本文分析了Fabry-Perot腔和微球腔的基本原理,通过CO2激光熔融光纤实验制得了直径为1.2 mm的微球腔,并测试了微球腔和锥形光纤耦合结构的耦合特性.采用典型的PDH稳频系统设计了基于微球腔的稳频系统,分析了用于鉴频的误差曲线的吸收特性和色散特性,对比了不同调制频率、微球腔直径、耦合损耗、传输损耗下与误差曲线斜率的关系.结果表明:耦合状态下最大Q值可达到1.1×108,调节微球腔内横磁模和横电模的转换可优化耦合效率,匹配微球腔和锥形光纤的尺寸得到了径向二阶模式的透射谱,误差曲线效率达到15.4A mW/MHz.球腔在提高PDH稳频技术灵敏度上具有巨大潜力. 相似文献
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ESR and ENDOR experiments using a disc-shaped resonator working in the Whispering Gallery Mode (WGM)
Different instrumental apparatuses are presented employing disc-shaped dielectric resonators working in the Whispering Gallery Mode (WGM). The conditions suitable to take the best from the microwave power obtained from a trade klystron in the X-band have been verified for the ESR part of the experiments. It is well known that a good ESR saturation condition is an essential prerequisite to have satisfactory ENDOR results. The WGM dielectric resonators seem to be very suitable for multiple irradiation purposes and in particular for ENDOR experiments which is the aspect we wanted to exploit here. Various radiofrequency ENDOR irradiation circuits have been tested and the obtained spectra of a γ-irradiated single crystal are presented and criticized. Some results for very high frequency ESR applications are also reported. 相似文献
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Wallraff A Ustinov AV Kurin VV Shereshevsky IA Vdovicheva NK 《Physical review letters》2000,84(1):151-154
Experiments indicating the excitation of whispering-gallery-type electromagnetic modes by a vortex moving in an annular Josephson junction are reported. At relativistic velocities the Josephson vortex interacts with the modes of the superconducting stripline resonator giving rise to novel resonances on the current-voltage characteristic of the junction. The experimental data are in good agreement with analysis and numerical calculations based on the two-dimensional sine-Gordon model. 相似文献
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Whispering gallery mode (WGM) optical microresonators have attracted intense interests in the past decades. The combination of high quality factors (Q) and small mode volumes of modes in WGM resonators significantly enhances the light‐matter interactions, making them excellent cavities for achieving low threshold and narrow linewidth lasers. In this Review, the progress in WGM microcavity lasers is summarized, and the laser performance considering resonator geometries and materials as well as lasing mechanisms is discussed. Label‐free detection using WGM resonators has emerged as highly sensitive detection schemes. However, the resolution is mainly limited by the cavity Q factor which determines the mode linewidth. Microcavity lasers, due to their narrow laser spectral width, could greatly improve the detection resolution. Some recent developments in sensing using microcavity lasers are discussed. 相似文献