Widely tunable sub-nanosecond microcavity optical parametric oscillator based on cavity phase matching

Due to the excessively short pulse width and low repetition rate, sub-nanosecond lasers face inherent challenges in pumping conventional optical parametric oscillators (OPOs) and cannot support synchronous pumping, thereby limiting the development of high-performance frequency converters. This work demonstrates the first, to the best of our knowledge, sub-nanosecond frequency conversion based on KTP microcavity optical parametric oscillators (MOPOs). Pumped by a 532 nm laser at a 1 kHz repetition rate, the MOPO provided temperature-tunable outputs around 1.06 μm with stepped mode hopping. A 200 μm microcavity enabled signal and idler tuning ranges of 32.16 nm and 35.80 nm, respectively, and the maximum output power of 11.3 mW was obtained in a 260 μm microcavity. The signal pulse width was around 355 ps, with the spectral bandwidth of approximately 60 pm. This method eliminates specific material and wavelength constraints on nonlinear crystals, showing excellent potential in extending the sub-nanosecond laser wavelength for various applications.