OPTICAL PARAMETRIC OSCILLATION EXCITED BY AN INCOHERENT CONICAL BEAM

The operation of a KTP optical parametric oscillator pumped by an inco herent conical beam is demonstrated for the first time. The incoherent conical beam was produced by nonaxial excitation of a multimode fiber . It is shown that the OPO output radiation pattern in the far field c onsists of a coherent central spot (signal) and an incoherent ring (id ler). The incoherence of the pump was transferred to the idler wave in accordance with theoretical predictions. By adjusting the OPO cavity mirrors, the lowest-order mode as well as higher-order transverse mode s were easily selected in the central spot. (C) 1997 Elsevier Science B.V.