Storing optical information as a mechanical excitation in a silica optomechanical resonator

We report the experimental demonstration of storing optical information as a mechanical excitation in a silica optomechanical resonator. We use writing and readout laser pulses tuned to one mechanical frequency below an optical cavity resonance to control the coupling between the mechanical displacement and the optical field at the cavity resonance. The writing pulse maps a signal pulse at the cavity resonance to a mechanical excitation. The readout pulse later converts the mechanical excitation back to an optical pulse. The storage lifetime is determined by the relatively long damping time of the mechanical excitation.     

Transverse mode coupling in an optical resonator

Small-angle scattering due to mirror surface roughness is shown to couple the optical modes and deform the transmission spectra in a frequency-degenerate optical cavity. A simple model based on a random scattering matrix clearly visualizes the mixing and avoided crossings between multiple transverse modes. These effects are visible only in the frequency-domain spectra; cavity ringdown experiments are unaffected by changes in the spatial coherence, as they probe just the intracavity photon lifetime.     

外电场作用下二氧化硅分子的光激发特性研究

采用密度泛函B3P86和组态相互作用方法在6-311G**基组水平上计算了二氧化硅分子从基态到前5个激发态的跃迁波长、振子强度、自发辐射系数A_n0和吸收系数B_0n（n=1—5）.研究了外电场对二氧化硅分子激发态的影响规律. 结果表明,随外电场强度增大,最高占据轨道与最低空轨道能隙变小,占据轨道的电子易于激发至空轨道. 因而在外场作用下分子易于激发. 关键词： 2')" href="#">SiO₂ 激发态 外电场     

Laser phase and frequency stabilization using an optical resonator

We describe a new and highly effective optical frequency discriminator and laser stabilization system based on signals reflected from a stable Fabry-Perot reference interferometer. High sensitivity for detection of resonance information is achieved by optical heterodyne detection with sidebands produced by rf phase modulation. Physical, optical, and electronic aspects of this discriminator/laser frequency stabilization system are considered in detail. We show that a high-speed domain exists in which the system responds to the phase (rather than frequency) change of the laser; thus with suitable design the servo loop bandwidth is not limited by the cavity response time. We report diagnostic experiments in which a dye laser and gas laser were independently locked to one stable cavity. Because of the precautions employed, the observed sub-100 Hz beat line width shows that the lasers were this stable. Applications of this system of laser stabilization include precision laser spectroscopy and interferometric gravity-wave detectors.     

Effect of RF coil excitation on field inhomogeneity at ultra high fields: a field optimized TEM resonator

In this work, computational methods were utilized to optimize the field produced by the transverse electromagnetic (TEM) resonator in the presence of the human head at 8 Tesla. Optimization was achieved through the use of the classical finite difference time domain (FDTD) method and a TEM resonator loaded with an anatomically detailed human head model with a resolution of 2 mm × 2 mm × 2 mm. The head model was developed from 3D MR images. To account for the electromagnetic interactions between the coil and the tissue, the coil and the head were treated as a single system at all the steps of the model including, numerical tuning and excitation. In addition to 2, 3, 4, 6, and 10-port excitations, an antenna array concept was utilized by driving all the possible ports (24) of a 24-strut TEM resonator. The results show that significant improvement in the circularly polarized component of the transverse magnetic field could be obtained when using multiple ports and variable phase and fixed magnitude, or variable phase and variable magnitude excitations.     

On the analogy between a single atom and an optical resonator

A single atom in free space can have a strong influence on a light beam and a single photon can have a strong effect on a single atom in free space. Regarding this interaction, two conceptually different questions can be asked: can a single atom fully absorb a single photon and can a single atom fully reflect a light beam. The conditions for achieving the full effect in either case are different. Here we discuss related questions in the context of an optical resonator. When shaping a laser pulse properly it will be fully absorbed by an optical resonator, i.e., no light will be reflected and all the pulse energy will accumulate inside the resonator before it starts leaking out. We show in detail that in this case the temporal pulse shape has to match the time-reversed pulse obtained by the cavity’s free decay. On the other hand a resonator, made of highly reflecting mirrors which normally reflect a large portion of any incident light, may fully transmit the light, as long as the light is narrow band and resonant with the cavity. The analogy is the single atom—normally letting most of the light pass—which under special conditions may fully reflect the incident light beam. Using this analogy we are able to study the effects of practical experimental limitations in the atom-photon coupling, such as finite pulses, bandwidths, and solid angle coverage, and to use the optical resonator as a test bed for the implementation of the quantum experiment.     

Effective excitation of quasi-optical resonator in millimeter wave

It is described effective excitation of quasi-optical resonator (Q. O. R) in millimeter wave (M. M. W) in this article in which some useful results are obtained.This research work was supported by National Natural Science Foundation of China. (No. 69171027)     

Coupled magnetic resonator optical waveguides

Optical resonators are important devices that control the properties of light and manipulate light–matter interaction. Various optical resonators are designed and fabricated using different techniques. For example, in coupled resonator optical waveguides, light energy is transported to other resonators through near‐field coupling. In recent years, magnetic optical resonators based on LC resonance have been realized in several metallic microstructures. Such devices possess stronger local resonance and lower radiation loss compared with electric optical resonators. This study provides an overall introduction on the latest progress in coupled magnetic resonator optical waveguide (CMROW). Various waveguides composed of different magnetic resonators are presented and Lagrangian formalism is used to describe the CMROW. Moreover, several interesting properties of CMROWs, such as abnormal dispersions and slow‐light effects, are discussed and CMROW applications in nonlinear and quantum optics are shown. Future novel nanophotonic devices can be developed using CMROWs.     

Disorder-immune coupled resonator optical waveguide

We demonstrate that a photonic lattice with short- and long-range harmonic modulations of the refractive index facilitates formation of flat photonic bands and leads to slow propagation of light. The system can be considered a coupled-resonator optical waveguide (CROW): photonic bands with abnormally small dispersion are created due to the interaction of long-lived states in the cavity regions via weak coupling across tunneling barriers. Unlike previous CROW implementations, the proposed structures can be fabricated with interference photolithography (holography), sidestepping the issue of resonator-to-resonator fluctuation of the system parameters. The proposed holography-based approach enables fabrication of arrays with a large number of coupled optical resonators, which is necessary for practical applications.     

Experimental investigation of an active open optical resonator in a turbulent atmosphere

The spectral densities of the time fluctuations of the amplitude of steady-state generation at two wavelengths ₁=0.63 and ₂=1.15 under conditions of turbulent fluctuations of the refractive index in the waveguide channel of an open optical resonator are studied. The frequency dependences of the spectral densities are analyzed at various states of atmospheric turbulence, including the state produced in an aerodynamic chamber. For wavelength ₂ the fluctuations of the water-vapor content form a random absorption field. The distinctive features of the frequency dependence of the spectral density are discussed and related to the time cross-correlation of random fields of the passive impurity of the water-vapor concentration, the temperature, and the turbulent velocity of the flow. The asymptotic behavior of the frequency dependences of the spectral density is analyzed from the standpoint of the self-similarity of the stochastic characteristics of the system consisting of the waveguide channel and the medium.Odessa Hydrometeorological Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 34, No. 2, pp. 111–118, February, 1991.     

Filamentary coagulation of particles from water-heterogeneous systems in the field of an acoustic resonator

The coagulation of particles from water-heterogeneous systems in the field of a confocal ultrasonic resonator is studied. It is found that, at frequencies of several megahertz, when acoustic power of about 1 W is applied to the resonator, long stable filaments consisting of the material of the heterogeneous system are formed in the vicinity of the resonator axis. The filaments consist of thin disks formed by coalescent particles spaced at intervals strictly equal to half of the sound wavelength. The features of this coagulation are determined for suspensions of various nature (metal and dielectric particles, colloidal solutions, and oil emulsions). It is established that the coagulation in a standing acoustic wave occurs faster than under natural conditions (under the influence of gravity). The possibility of using this effect for cleaning liquids from impurities and separating hyperfine particles without employing filter materials is discussed.     

Monofrequency excitation of open resonator with inclined comb grating

The theoretical and experimental analysis of the open resonator with the reflection diffraction comb grating has been presented. This resonator has excitation where is close to the monofrequency mode. This results may be used for the elaboration of mm-wave quasi-optical devices such as generators, mixer, converter, wavemeters and others.