Phase-locked degenerate backward wave optical parametric oscillator

We report a self-phase-locked and degenerate backward wave optical parametric oscillator (BWOPO) generating a counterpropagating signal and an idler in the spectral band of optical communication. The device is based on a periodically poled Rb-doped KTiOPO4 crystal with a poling period of 433 nm. To the best of our knowledge, this is the shortest quasi-phase matching period reported in the bulk of a ferroelectric crystal. The spectral and coherence properties of the BWOPO at degeneracy are investigated. We observe a single pass conversion efficiency of 40%. At degeneracy, the counterpropagating signal and idler generate phase-matched sum-frequency generation in both directions. We confirm the phase-locked state at degeneracy by interfering the pump with the frequency-doubled backward wave. The phase-locked state is stable during the entire duration of the experiment without active stabilization.
QC 20230316