Transverse structures in a triply resonant OPO: from optical patterns to quantum structures

Summary form only given. Spontaneous pattern formation has been widely studied both by experimentalists and theoreticians. But most of these studies have concentrated on optical systems having third order nonlinearities. Second order nonlinear effects have recently received a large interest. They provide at the same time a simple mechanism and a rich variety of phenomena because of the coupling between waves of different frequencies. Theoreticians have predicted various transverse patterns especially in the case of optical parametric oscillators (OPO). We have developed a c.w. OPO operating in cavities with degenerate transverse modes and observed spontaneous pattern formation due to second order nonlinearity.