Coupling channels in a photorefractive ring-resonator containing gain by two-wave-mixing

Abstract For many applications in modern nonlinear optics thresholding, switching and amplifying devices are of high interest. We investigated a photorefractive ring-resonator containing four lenses in an 8-f-geometry. Gain was provided by two-wave-mixing in a photorefractive BaTiO3-crystal leading to a unidirectional travelling wave in the cavity. Introducing an intracavity aperture in the image plane of the system produces two coupling channels with identical properties. The coupling takes places due to an overlap of the two channels within the photorefractive crystal standing in the Fourier-plane of the system.