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Continuous-Wave Single-Longitudinal-Mode Fiber-Optical Parametric Oscillator With Reduced Pump Threshold

A single-longitudinal-mode (SLM) fiber-optical parametric oscillator (FOPO) is proposed and demonstrated experimentally. The FOPO operates fundamentally by resonating the nondegenerate signal and idler in two separate optical cavities independently, combined with a subring cavity inserted inside the signal cavity as a mode restricting device. The proposed structure is first reported, to the best of our knowledge, which reduces the threshold pump power at a ratio of 38% compared with the usual singly resonant FOPO, and achieves an SLM oscillation with sidemode suppression ratio of greater than 51 dB.