Четырехволновое взаимодействие на фазово-амплитудных голографических решетках в фоторефрактивном пьезокристалле класса симметрии 43m

A system of coupled-wave equations for calculating the vector amplitudes of linearly polarized light waves at four-wave mixing by phase-amplitude holographic gratings in a cubic photorefractive semiconductor of an arbitrary cut belonging to the 4 ̅3m symmetry class is presented. The dependences of the intensities of the polarization components of the reversed light wave on the orientation angle for GaAs crystal of (110)-cut are calculated on the basis of the numerical solution of the system of coupled-wave equations. The obtained dependences are compared with the known theoretical and experimental data. It is shown that the best agreement between the results of theoretical modeling and experimental data at calculating the counterpropagating four-wave mixing in GaAs crystal of (110)-cut is achieved if formation of several phase-amplitude holographic gratings is allowed, and the contribution of the photoelastic and inverse piezoelectric effects are taken into account together with absorption of the crystal.

Semiconductor Laser Linewidth Theory Revisited

More and more applications require semiconductor lasers distinguished not only by large modulation bandwidths or high output powers, but also by small spectral linewidths. The theoretical understanding of the root causes limiting the linewidth is therefore of great practical relevance. In this paper, we derive a general expression for the calculation of the spectral linewidth step by step in a self-contained manner. We build on the linewidth theory developed in the 1980s and 1990s but look from a modern perspective, in the sense that we choose as our starting points the time-dependent coupled-wave equations for the forward and backward propagating fields and an expansion of the fields in terms of the stationary longitudinal modes of the open cavity. As a result, we obtain rather general expressions for the longitudinal excess factor of spontaneous emission (K-factor) and the effective α-factor including the effects of nonlinear gain (gain compression) and refractive index (Kerr effect), gain dispersion, and longitudinal spatial hole burning in multi-section cavity structures. The effect of linewidth narrowing due to feedback from an external cavity often described by the so-called chirp reduction factor is also automatically included. We propose a new analytical formula for the dependence of the spontaneous emission on the carrier density avoiding the use of the population inversion factor. The presented theoretical framework is applied to a numerical study of a two-section distributed Bragg reflector laser.

D'Alembert type travelling wave solution for a wave equations on finite interval with coupled initial boundary conditions

The problem of solving equations for a class of coupled wave equations with initial-boundary conditions is discussed by using the results for the problem with initial value in this paper. A coupled wave equations which defined in semi-infinite interval and finite interval are studied respectively, the d’Alembert type traveling wave solutions with finite closed form of the corresponding problems are obtained and the examples are given. This research generalize the corresponding results for single wave equation and .avoid the traditional Fourior series solution.