Thermooptical Sound Generation by Bessel Light Beams in Nonlinear Crystals

The peculiarities of thermooptical excitation of elastic waves in nonlinear crystals, which appear due to modulated absorption of the energy from a Bessel light beam at the second harmonic, were theoretically examined. The amplitude–phase characteristics of the photoacoustic signal were found, and the conditions of the most effective thermooptical excitation of the sound were determined. The received results can be used in the design of new optoacoustic scanners for diagnostics of subsurface structures and new quantum electronics and integrated optics devices.     

An All-optical Mechanism of Sub-poissonian Light Generation

Abstract

We investigate the interaction of two counterpropagating linearly polarized waves in a dielectric waveguide grating in the presence of an intensity-dependent contribution to the refractive index (optical Kerr effect). The resulting nonlinear distributed-feedback (DFB) mechanism responsible, from a classical point of view, for a marked limiting effect which stabilizes the intensity of one of the two waves, is shown to generate, once the problem is treated in a quantum-mechanical way, a field exhibiting sub-Poissonian photon statistics.     

Generation of bremsstrahlung by an electron beam

The problem of generation of x- and y-radiations in interaction of an electron beam with a layer of a substance having a large Z is considered theoretically. Energy and angular spectra of bremsstrahlung are obtained for various energies of the electron beam. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 5, pp. 887–890, September–October, 1998.     

Spectrum of Scattered Light by an Ionized Two-level Atom

Abstract

The spectrum of scattered light by an ionized two-level atom is investigated. The ionization is considered as a damping out of the ordinary two-level system and its effect on the spectrum is extracted. Because of the ionization damping, the central peak in the spectrum changes significantly according to the parameters involved. For a large ionization damping, a central dip is observed; for a small ionization damping, an additional sharp peak appears on top of the central peak.     

Light coupling into an optical microcantilever by an embedded diffraction grating

By measuring the excitation efficiency of an optical waveguide on a diffraction grating one can accurately register the changes in the incidence angle of the exciting light beam. This phenomenon was applied to detect ultrasmall deflections of silicon dioxide cantilevers of submicrometer thickness that were fabricated with corrugation on top to act as diffraction grating couplers. The power of light coupled into the cantilevers was monitored with a conventional photodetector and modulated using mechanical vibration of the cantilever, thus changing the spatial orientation of the coupler with respect to the incident light beam. The technique can be considered as an alternative to the methods known for detection of cantilever deflection.     

撞击流技术在发电相关领域的研究与应用进展

节能降耗是中国发电行业当前发展的主要方向。撞击流在撞击的瞬间能够产生极大的相间相对速度,并形成一个相对狭窄的高度湍动区,能够极好地提高热、质传递。撞击流的这种性质可被广泛应用于发电行业的相关领域,尤其是在燃烧、干燥、污水处理、脱硫脱硝、煤气化、除尘等领域具有广阔的应用前景。在简述撞击流技术基本原理的基础上,总结了近年来撞击流技术的研究进展,并就撞击流技术在发电行业相关领域的应用前景进行了讨论,以期为撞击流技术在发电行业的进一步应用提供参考。     

三代微光器件的测试和评估技术研究

在已有的负电子亲和势(NEA)光电阴极特性评估技术的基础上,研制了三代微光器件的测试和评估系统工程样机,用于对三代微光器件的光谱响应等参数的测试和激活过程中的工艺信息监控,通过分析计算可获得三代微光器件光电阴极的表面逸出几率、载流子扩散长度和后界面复合速率等参数.利用该系统对三代微光像增强器进行了测试和评估,文中给出了测试结果并加以分析.     

Light scattering by an infinite circular cylinder immersed in an absorbing medium

Analytic solutions are developed for the single-scattering properties of an infinite dielectric cylinder embedded in an absorbing medium with normal incidence, which include extinction, scattering and absorption efficiencies, the scattering phase function, and the asymmetry factor. The extinction and scattering efficiencies are derived by the near-field solutions at the surface of the particle. The normalized scattering phase function is obtained by use of the far-field approximation. Computational results show that, although the absorbing medium significantly reduces the scattering efficiency, it has little effect on absorption efficiency. The absorbing medium can significantly change the conventional phase function. The absorbing medium also strongly affects the polarization of the scattered light. However, for large absorbing particles the degrees of polarization change little with the medium's absorption. This implies that, if the transmitting lights are strongly weakened inside the particle, the scattered polarized lights can be used to identify objects even when the absorption property of the host medium is unknown, which is important for both active and passive remote sensing.     

Light diffraction by a particle on an optically smooth surface

The differential cross section for radiation scattered by a particle that is large compared to the wavelength, and resting on an optically smooth surface, is characterized by an intense, narrow peak in the direction of the reflected beam. This peak is shown to be due mainly to Fraunhofer diffraction by the overlapping projections of the particle and its image on a plane perpendicular to the reflected beam. Results calculated with this simple diffraction theory are compared with accurate results calculated by the multipole expansion method. Simple analytic formulas are derived that characterize the width and height of the central diffraction peak.     

Solution of the Poisson equation by differential quadrature

The method of differential quadrature is demonstrated by solving the two-dimensional Poisson equation. The results for three test problems are compared with the exact analytical solutions and the numerical solutions obtained by others for the Galerkin, the control-volume and the five-point finite difference methods. The method of differential quadrature leads to more accurate results for comparable levels of computational effort.     

Experimental Progress in Intracavity Generation of Squeezed Light Using Resonant Atomic Nonlinearities

Abstract

Quantum-noise reduction to levels nearly 1 dB below the standard quantum limit are reported for light frequencies near an atomic-sodium resonance. This squeezed light is generated in an optical confocal cavity using four-wave mixing due to the atomic-sodium resonance nonlinearity. Squeezed light exits the cavity through a partially reflecting mirror and is detected outside the cavity with a balanced homodyne detector. Experimental details are described for minimizing losses in the atomic beam and detection apparatus. Frequency jitter due to the pump laser also plays a key role in the limits for noise reduction. A wideband phenomenological model is used to analyse the results. Good agreement between this model and the experimental results is obtained. A full quantum model also agrees with the results and predicts even larger squeezing at higher pump intensities. Prospects for achieving this larger-noise-reduction regime are good.     

Generation of single-cycle pulses spaced by an integer number of molecular periods

Abstract

Previous work has shown that a new light source consisting of mutually coherent spectral sidebands ranging from 2.94 μm to 195 nm can be obtained by adiabatic preparation of a molecular ensemble in a single vibrational superposition state. Molecular motion modulated the refractive index and thus led to the frequency modulation of the driving beat-note. The resulting sidebands were equidistant and separated by a frequency equal to the modulation frequency. In the present work we extend this idea by applying more input fields to the molecular ensemble. We take two input fields separated by one half of the modulation frequency, such that their second harmonics drive the molecular ensemble. The proposed approach results in generating an equidistant comb of frequencies separated by a fraction (1/4) of the modulation frequency. Moreover, the intensity of the generated train of pulses increases by the inverse of the same factor. An important feature of the generated comb is that it reaches zero frequency, and as a consequence allows for control of the absolute phase, or the phase of the carrier with respect to the envelope. Since many physical processes, for example photoionization of molecules by intense laser pulses, are influenced by the time dependence of the electric field (and not the envelope), control of absolute phase will become an important issue for few-cycle pulses.     

Light scattering by a coated infinite cylinder in an absorbing medium

The scattering formulation for a coated infinite cylinder in an absorbing medium is presented in this paper. The cylinder is subjected to an arbitrarily polarized plane wave propagating in a general direction at the cylinder. The refractive index and magnetic permeability of the host medium, as well as those for the core and coating of the cylinder, can be real or complex. The scattering and extinction efficiencies and the scattering amplitudes are derived for both the near field and the far field. As the medium is absorbing, the "true" extinction and scattering efficiencies are derived based on the radiative energy outflow at the surface of the cylinder. The radiative efficiencies in the far field are denoted as "apparent" properties because they include absorption by the intervening medium. The influence of the refractive index and permeability of the host medium on the scattering properties of a coated cylinder is illustrated by numerical examples.     

Two-Parameter Observation of Correlated Poisson Signals in Poisson Noise

Computer simulation is used to derive the probabilities of errors involving overlooking the signal and false alarm as governed by the correlation coefficient between channels for two-parameter signal observation.Translated from Izmeritel’naya Tekhnika, No. 3, pp. 9–11, March, 2005.     

The Generation of Compact Quasi-Spherical Plasma Formations by an HF Inductive Discharge

Inductors of a new type are developed for producing HF discharges, which represent frames of convex polyhedrons. In these inductors, stationary compact plasma formations are generated whose shape is close to spherical. The plasma produced in these inductors exhibits a higher concentration of electrons, as well as a visually higher specific glow intensity per unit volume, than those in the known spiral-based inductors.     

Generation of Electron Bunches by an Ultrarelativistic Laser Pulse Intersecting the Boundary of an Inhomogeneous Plasma

Technical Physics Letters - The mechanism of generation of electron bunches upon the interaction of a laser pulse with a semibounded plasma having a diffuse boundary with vacuum in the form of a...     

Nonlinear systems driven by polynomials of filtered Poisson processes

The perturbation method is applied to determine approximately the mean, variance, skewness and kurtosis of the transient and stationary response of nonlinear systems driven by polynomials of filtered Poisson processes. The analysis is based on the classical perturbation method, the Itô differentiation formula, and properties of the response of linear systems subjected to polynomials of filtered Poisson processes. Two examples are presented to demostrate the efficiency and accuracy of this approximate analysis.     

Generation of adjustable partially coherent bottle beams by use of an axicon-lens system

We report, what is to our knowledge, the first experimental realization of partially coherent bottle beams. It is shown that partially coherent bottle beams can be achieved by the focusing of partially coherent light with an axicon-lens system. The influence of the spatial coherence of the incident partially coherent light and other parameters, such as the radius of the limiting aperture of the axicon and the distance between the axicon and the lens, on the size of the bottle beams is investigated. We find that the longer the spatial coherence length, the larger the size of the resultant bottle beams. This dependence of the size of the bottle beams on the spatial coherence of the incident light provides a facile approach for generating adjustable partially coherent bottle beams. This kind of partially coherent bottle beam may have applications in atom optics, such as in atom trapping and atom guiding, etc.