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 共查询到20条相似文献,搜索用时 171 毫秒
1.
程首宪  程嗣 《物理实验》2004,24(7):30-31
凡惯性定律成立的参照系,叫做惯性系;惯性定律不成立的参照系,叫做非惯性系.牛顿第一定律和第二定律在非惯性系中是不适用的.因此,在研究动力学问题时通常应选择惯性系做为参照系.为了在非惯性系中仍能应用牛顿运动定律,往往需引入惯性力的概念.但如果不是使用惯性力的概念,而是同时考虑非惯性系的变速运动以及质点相对非惯性系的相对运动,则在惯性系中使用牛顿运动定律依然方便.  相似文献   

2.
陆世专  余洪伟 《中国物理快报》2005,22(10):2481-2484
We study a two-level atom in interaction with a real massless scalar quantum field in a spacetime with a reflecting boundary. We calculate the rate of change of the atomic energy for the atom. The presence of the boundary modifies the quantum fluctuations of the scalar field, which in turn modifies the rate of change of the atomic energy. It is found that the modifications induced by the presence of a boundary make the spontaneous radiation rate of an excited atom to oscillate near the boundary and this oscillatory behaviour may offer a possible opportunity for experimental tests for geometrical (boundary) effects in flat spacetime.  相似文献   

3.
The design and performance of a Micromegas with a resistive anode are presented in this paper. A thin resistive sheet with volume resistivity of 1012 Ω·m cm is glued onto the readout electrode surface and its performance is investigated by using a 55Fe X-ray radioactive source in the operation gas of argon and isobutene mixtures (Ar/Iso=95/5). The gas gain at different mesh high voltage, counting rate and working time are given. Energy spectra at different working voltages are measured and the results are discussed. We have oberved that a Micromegas with a resistive anode can be operated at higer gain than a standard Micromegas without sparks.  相似文献   

4.
We study the random motion of a charged test particle coupled to electromagnetic vacuum fluctuations near a perfectly reflecting plane boundary with a nonzero classical constant velocity in a direction parallel to the plane. We calculate the mean squared fluctuations in the velocity and position of the test particle taking into account both fluctuating electric and magnetic forces. Our results show that the influence of fluctuating magnetic fields is, in general, of the higher order than that caused by fluctuating electric fields and is thus negligible.  相似文献   

5.
We built a numerical model for evaluating the coupling processes of a mixed structure of a Bragg fiber grat-ing and a long-period grating. From the numerical results, we not only confirmed the wavelength switchingphenomena observed in previously reported experiments, but also discovered a new coupling mechanism,which generated the reflection of a signal with its wavelength longer than the Bragg wavelength. Thedependencies of the wavelength switching behaviors on various parameters of the mixed grating structure  相似文献   

6.
We present a numerical study of a model of quantum walk in a periodic potential on a line. We take the simple view that different potentials have different affects on the way in which the coin state of the walker is changed. For simplicity and definiteness, we assume that the walker's coin state is unaffected at sites without the potential, and rotated in an unbiased way according to the Hadamard matrix at sites with the potential. This is the simplest and most natural model of a quantum walk in a periodic potential with two coins. Six generic cases of such quantum walks are studied numerically. It is found that, of the six cases, four cases display significant localization effect where the walker is confined in the neighborhood of the origin for a sufficiently long time. Associated with such a localization effect is the recurrence of the probability of the walker returning to the neighborhood of the origin.  相似文献   

7.
The fourier-transform patterns of an object are usually observed in the far-field region or obtained in the near-field region with the help of lenses. Here we propose and experimentally demonstrate a scheme of Fourier-transform patterns in the Fresnel diffraction region with thermal light. In this scheme, neither a lens nor a beamsplitter is used, and only one single charge coupled device(CCD) is employed. It means that dividing one beam out of a light source into signal and reference beams is not as necessary as the one done by the use of a beamsplitter in usual ghost interference experiments.Moreover, the coincidence measurement of two point detectors is not necessary and data recorded on a single CCD are sufficient for reconstructing the ghost diffraction patterns. The feature of the scheme promises a great potential application in the fields of X-ray and neutron diffraction imaging processes.  相似文献   

8.
A new method is introduced to generate a hollow beam inside a cavity.Using a matrix eigenvalue method,the laser resonator with optical diffraction elements is theoretically analysed and simulated.The hollow beam can be obtained theoretically by controlling the parameters of the diffraction functions.After designed the diffraction components in the cavity,a hollow beam of good quality is realized experimentally using a YAG solid state laser.  相似文献   

9.
Pranab Sarkar 《Pramana》2000,54(3):385-392
We present a numerical investigation of quantum mechanical tunneling process in a double well potential with fluctuating barrier. The tunneling probability and rate are calculated for two cases in which (i) the height of the barrier is undergoing harmonic oscillation with frequency θ and (ii) the height of the barrier is undergoing random fluctuation with frequency θ. It is observed that in both cases, the quantum mechanical tunneling probability and rate exhibit a maximum as a function of the fluctuation frequency. The optimal frequency i.e. the frequency at which rate exhibits a maximum shows a strong isotopic mass effect.  相似文献   

10.
11.
The propagation properties and field structures of a new class of electromagnetic surface excitations, the so-called guided surface polaritons, are investigated. These waves exhibit features of both film-guided modes and surface polaritons. The conditions of their existence dependent on the optical constants are discussed. The three-dimensional waveguide problem is treated by a rigorous mathematical formalism.  相似文献   

12.
We report one- and two-dimensional arbitrary patterns which are achieved by nanocavity waveguides made of a quasi-metal?Cdielectric-metal heterostructure with omnidirectional illumination. This proposed heterostructure supports the surface plasmon polaritons whose phase and group velocities have opposite sign for given frequency. Negative refraction and reflection in the waveguide result in imaging nanolithography and the omnidirectional property can be well understood by the dispersive relation of the nanocavity waveguide. Numerical results demonstrate that such an omnidirectional nanolithography scheme is feasible for arbitrary 1D gratings and 2D linearly chirped gratings with TM and circular polarized incidence, respectively, at 365?nm.  相似文献   

13.
<正>Light propagation through a metal/nonlinear dielectric material/metal(M-NL-M) structure is numerically studied.The design parameters of the M-NL-M structure are found with the waveguide theory so that the structure only supports the symmetric surface plasmon polaritons(SPP(0)) mode and the antisymmetric surface plasmon polaritons(SPP(1)) mode.The coupling between the two modes within the M-NL-M structure is exploited.Through controlling the propagation constants of the two modes with the intensity-dependent dielectric constant of the nonlinear Kerr material,an effective all-optical control of plasmonic signal modulator can be realized with this M-NL-M structure.  相似文献   

14.
We analyze the coupling between surface plasmon polaritons in a metal grating and the guided modes of a dielectric waveguide. Our model structure is a gold wire grating on a slab waveguide made of silicon nitride on silica wafer. The excitation of guided-mode resonances, surface plasmon polariton modes and hybrid waveguide-plasmon modes are observed in numerical simulations. Our experiments verify the existence of the predicted modes. These hybrid modes add significant degrees of freedom in designing structures for plasmonic applications.  相似文献   

15.
Tutt L  Revelli JF 《Optics letters》2008,33(5):503-505
The angular distribution of radiation emitted from organic electroluminescent diodes fabricated on substrates with wavelength-scale gratings was measured using an optical Fourier transform instrument. A simple geometrical model is derived that specifies the polar angle of the exiting photon as a function of the azimuth angle, the grating pitch, the wavelength of light, and the effective index of the refraction of the light emitted by the fluorescing excitons. The radiation pattern of the extracted light is shown to fit that predicted by the model if one assumes that it comes from surface plasmon polaritons and bound TE waveguide modes.  相似文献   

16.
Polarization-dependent structures have been formed on the silicon surface under the action of femtosecond laser pulses. Some model concepts are proposed to describe changes in the response of the semiconductor surface caused by the generation of a nonequilibrium electron-hole plasma and explain the excitation of surface polaritons and waveguide modes during a femtosecond laser pulse.  相似文献   

17.
A theory is constructed for the reflection of plane electromagnetic waves in uniaxial crystals with a positive definite permittivity tensor and an arbitrarily oriented metallized boundary. The problem is solved both for general-position orientations corresponding to three-partial reflection and for special conditions allowing two-partial reflections: mode conversions when the incident and reflected waves belong to different sheets of the refraction surface and “pure” reflections when both waves belong to the same sheet. The space of pure reflections is shown to be formed by two types of optical-axis orientations: arbitrary directions in the plane of the crystal surface and in the plane of incidence. The configurations of the conversion surface for optically positive and negative crystals are investigated. A subspace of pure reflections that transform into one-partial bulk polaritons with the energy flux parallel to the surface at grazing incidence has been found. The domain of existence of such bulk eigenmodes is bounded by two “lines” of solutions. These are any directions along the boundary containing the optical axis for ordinary polaritons and the direction along the projection of the optical axis onto the surface at an arbitrary orientation of the axis with respect to the boundary for extraordinary polaritons.  相似文献   

18.
Lin CI  Gaylord TK 《Optics letters》2010,35(22):3814-3816
We report experimental excitation and characterization of surface plasmon modes in planar metal-insulator-metal (MIM) waveguides. Our approach is based on determining the width of the reflection angular spectrum in the attenuated total reflection (ATR) configuration. Owing to its transverse character, the ATR configuration provides a more straightforward and simpler way to determine the loss of plasmonic modes in MIM structures, compared to using tapered end couplers with multiple waveguide samples or scanning near-field optical microscopy. In this Letter, two waveguide structures with Au claddings and 50/200 nm SiO(2) cores are investigated. The propagation lengths measured at λ = 1.55 μm are 5.7 and 18 μm, respectively, in agreement with the theoretical predictions.  相似文献   

19.
The use of surface-impedance and surface-admittance concepts for analyzing reflection and refraction at an isotropic dielectric interface (first developed about 1938) is extended to include an interface between uniaxial birefringent dielectrics. Total internal reflection and the polarizing (Brewster) angle at an anisotropic interface are shown to be naturally explainable in terms of surface impedance (for TM polarization) and surface admittance (for TE polarization). The allowable modes in an integrated optical uniaxial asymmetric dielectric slab waveguide are also shown to be directly obtainable using the surface impedance/admittance approach. Numerical examples are presented.  相似文献   

20.
In this work we have observed the interaction of waveguide modes and surface polaritons arising on the surface of a semiconductor in proximity to a dielectric wave-guide. It is shown that at frequencies for which the phase velocities of these waves coincide, there arises a resonant interaction between them, allowing the emergence of a reflected signal in the dielectric waveguide. The amplitude of this signal varies periodically with a change in the length of the semiconductor. The results that have been obtained have been able to be used as a diagnostic for semiconductor materials as well as for the excitation of surface polaritons with the aid of a dielectric waveguide.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 78–83, January, 1989.  相似文献   

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