Observation of two distinct phase states in a self-phase-locked KTP optical parametric oscillator

Summary form only given. A self-phase-locked optical parametric oscillator (OPO) is potentially useful in quantum optics for studying nonclassic light and in precision measurements for constructing low phase-noise frequency dividers. We have demonstrated self-phase-locking in a type II phase matched OPO by adding an intracavity quarter-wave plate (QWP) to a KTiOPO/sub 4/ (KTP) OPO. The QWP provided polarization mixing between the orthogonally polarized signal and idler, and mutual injection locking was induced when their frequency difference was within the capture range. In this work, we report theoretical and experimental study of a KTP OPO under self-phase-locked conditions showing that there are two and only two phase states that have different thresholds and signal idler phase differences.