<title>Spontaneous polarization symmetry breaking in gas lasers and its observation possibilities</title>

Abstract

ABSTRACT Experimental results containing the dynamical behavior of the Nd-doped optical fiber laser are presented. It isfound that the state of pump polarization affects the intensity ratio of polarization modes. The intensity fluctuationspectrum of each polarization mode reveals three relaxation peaks. The model of a class B laser with two orthogonalelliptically-polarized modes is eligible for explanation of the main experimental features of relaxation oscillation peaks.Keywords: optical fiber laser, polarization mode, angular hole burning. 1. INTRODUCTION Most of the available dynamical models that provide an exact and fairly comprehensive description of themultimode class B lasers behavior are based on simplifying (though unaffectting the generality) assumptions for treatment of laser modes and laser medium. In particular, it is commonly assumed that cavity eigenmodes have the samepolarization (linear, as a rule). Another ordinary assumption is that a laser medium contains linearly-polarized dipolemoments of the same orientation1. Sometimes the model constructed on these hypotheses does not fit the real situation.Specifically, this concerns fiber lasers. Ignoring field polarization it is impossible to explain antiphase oscillations of theorthogonally polarized modes intensities in a Nd-doped fiber or the dependence of the relaxation oscillationsfrequencies on an ellipticity of counterrunning waves in a solid-state Nd-YAG ring laser with a non-plane cavity3.In this paper we substantiate the model of a class B laser with elliptically-polarized modes and compare thetheoretical conclusions with the experimental data obtained in a Nd-doped fiber laser.