Two-dimensional coupled mode equation for grating waveguide excitation by a focused beam

The problem of grating coupling of a focused incident beam under non-normal incidence into a slab waveguide is given a complete three-dimensional (3D) solution. The diffracted field is expressed as the Fourier integral of a regular part and of a singular part resulting from the existence of the coupled guided mode. A suitable expression of the field in the neighborhood of the pole and a rigorous definition of the modal field lead to a generalized coupled mode equation relating the incident field and the two-dimensional (2D) modal field propagating in the plane of the slab waveguide. The phenomenological parameters involved in the coupled wave equation: the propagation constant, the radiation coefficient as well as the modal field shape are derived from the exact treatment of plane wave diffraction in the same structure. The solution of the complete coupling problem is given in the particular case of a Gaussian incident beam, and of a high index step-index waveguide.     

The non-linear interaction of a powerful light beam with crystal lattice vibrations

The interaction of a powerful light beam with a one dimensional crystal lattice consisting of anisotropic and axially symmetric molecules is discussed. Translational and rotational vibrations are taken into account.     

Photon statistics of non-stationary gaussian-markovian light

The photon counting distribution due to gaussian-markovian light relaxing from an excited state to equilibrium, is calculated and compared with the distribution due to stationary light having the same average intensity.     

Enhanced two-photon fluorescence excitation by resonant grating waveguide structures

Enhanced two-photon fluorescence (TPF) spectroscopy with novel high-finesse resonant polymeric grating waveguide structures (GWSs) is presented. Under resonant conditions the field enhancement at the surface of a GWS can be exploited for TPF spectroscopy without the need for highly focused laser excitation light. We compare the TPF obtained by placing a drop of tetramethylrhodamine (TMR) on top of a GWS with that obtained with TMR on top of a glass substrate. Our procedure and results indicate that the detection of TPF can be improved by a factor of 10 with resonant GWSs.     

Oscillatory excitation of a non-linear system by a constant force

It is shown how a constant force can excite oscillations in a non-linear system.     

On excitation of a near-surface waveguide by a high-elevation source

Institute of Radio Engineering and Electronics, Russian Academy of Sciences Moscow. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 9, pp. 913–919, September, 1995.     

Transformation of photo-counting statistics by non-linear light conversion

It is known [1–3] that the statistical properties of the electrons emitted by a detector, which registers a light beam, contain information about light radiation statistics. This method has recently been widely used to measure the statistical properties of laser radiation [4]. In analysing non-linearly-transformed laser or thermal radiation, this method can give information about the non-linear process and also additional data on the statistics of the transformed radiation.     

Response statistics of discretized structures to non-stationary random excitation

Closed-form time-dependent response statistics such as (i) the variance of displacement response and variance of velocity response, (ii) the covariance of displacement and velocity responses, and (iii) covariances of displacement responses and velocity responses of structures, discretized by the finite element method, subjected to a wide class of non-stationary random excitations are presented. The response statistics include the contribution due to the evolutionary coincident and quadrature spectral density functions. Application of the expressions obtained has been made to a quarter-scale physical model of a class of mast antenna structures excited at the base. Computed results indicate that the contribution due to the evolutionary quadrature spectral density function is insignificant.     

Ion wave excitation by radiation pressure in a plasma waveguide

After turn-off of high-power pulsed microwaves, a large-amplitude ion wave is generated which has half of the wavelength of the guided wave. The electromagnetic radiation pressure is responsible for the excitation of the ion acoustic wave.     

Electromagnetic-wave excitation and diffraction by metal cylinder inside flat waveguide

Electromagnetic-wave excitation by a vertical electric dipole located inside a flat waveguide containing a vertical circular metal cylinder is examined. An exact solution is obtained, and the diffracted field inside the waveguide is analyzed. Algorithms are provided for electromagnetic-field calculation in a Rayleigh approximation and in a short-wave approximation. Results of numerical calculations of fields and directivity characteristics are presented. The effect of the cylinder on the radiation power of the dipole in the waveguide is analyzed.Nizhny Novgorod State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 36, No. 11, pp. 965–976, November, 1993.     

Efficiency of excitation of a quasioptical open resonator by a waveguide

We study theoretically and experimentally the efficiency of excitation of an open resonator by a waveguide. A two-dimensional model of a quasioptical two-mirror open resonator, which is excited through a coupling element in the form of an open end of a plane-parallel waveguide, is proposed. The field of the open resonator is represented as the superposition of Gaussian wave beams and its scattering on the coupling element is described by solving the problem of diffraction of waveguide waves and Gaussian wave beams on an open end of a flanged waveguide. Properties of the mirrors and the resonator loss are specified from physical considerations. The calculation results are compared with the experimental data, and a physical interpretation of the obtained results is offered. The factors which influence the efficiency of excitation of an open resonator are identified. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 52, No. 3, pp. 231–249, March 2009.     

High-order mode of polymeric waveguide selective excitation

Conditions for the selective excitation of multimode waveguide high-order modes by power trans-formation of fundamental modes of a tunnel connected waveguide are calculated. It is shown that the power conversion factor can reach 100% under phase-matching conditions, which can be satisfied by the selection of a second waveguide refractive index.     

A planar waveguide beam splitter

A 50:50 beam splitter for the light and matter waves based on a planar waveguide is studied. The light version of such a beam splitter is demonstrated experimentally. Applications of such a beam splitter in atom optics, interferometry and lithography are discussed.     

An iterative method for non-stationary response analysis of non-linear random systems

A method for calculating the non-stationary response of non-linear systems subjected to random excitations is formulated. The time-dependent equivalent linear system is considered and an iterative procedure for evaluating the non-stationary mean-square responses is developed. Several examples are presented and applicability of the technique is illustrated.     

Identification of the structure parameters using short-time non-stationary stochastic excitation

In this paper, we propose an approach to the flexural stiffness or eigenvalue frequency identification of a linear structure using a non-stationary stochastic excitation process. The idea of the proposed approach lies within time domain input-output methods. The proposed method is based on transforming the dynamical problem into a static one by integrating the input and the output signals. The output signal is the structure reaction, i.e. structure displacements due to the short-time, irregular load of random type. The systems with single and multiple degrees of freedom, as well as continuous systems are considered.     

Computation of higher-order waveguide modes by imaginary-distance beam propagation method

Abstact Yevick and Hermansson presented an efficient numerical method for calculating fundamental modes of optical waveguides. We extend their technique to higher-order eigenmodes. Using a finite-difference beam propagation method, we obtain propagation constants and field profiles for the three lowest-order TE modes in an asymmetric rib waveguide.