Experimental modal analysis of the spatiotemporal dynamics of a linear photorefractive phase-conjugate resonator

Abstract

An experimental modal analysis is performed on the transverse patterns of a photorefractive phase-conjugate resonator with a Karhunen–Loeve decomposition from which the most significant eigenvectors of the covariance matrix or the cross-spectral density matrix of the intensity fluctuations are defined and interpreted as the active eigenmodes of the resonator. The dynamics are studied as a function of the cavity Fresnel number and the angular tilt between the external pump beams (Bragg mismatch). As the Fresnel number is varied it is shown that states with the same modal decomposition may be temporally periodic or aperiodic. The Bragg mismatch is shown to be responsible for breaking the rotational symmetry of the system, changing the spatial complexity of the patterns, and changing the characteristic speed of the nonstationary patterns.