Comparative study of the green-pumped LBO crystal type-I and type-II phase-matched optical parametric oscillator

The study examines two LBO phase-matched (PM) configurations for near-infrared (NIR) optical parametric oscillators (OPOs) pumped by a 532 nm laser. The type-I PM LBO OPO generated an 1118 nm idler with an 11.4 ns pulse duration and an output power of 635 mW. The conversion efficiency was 27.6% and a spectral linewidth was ~23.2 nm. The temperature tuning range was 3.5 ℃, corresponding to an average wavelength tuning rate of ~22 nm/℃. The beam quality factor M² was measured to be about 3.05. The type-II PM LBO OPO generated an 1116 nm idler with an 8.0 ns pulse duration and an output power of 424mW, achieving an 18.4 % conversion efficiency and a spectral linewidth of ~1.3 nm. The temperature tuning range was 130 ℃, corresponding to an average wavelength tuning rate of ~0.77 nm/℃. And the beam quality factor M² was measured to be about 2.50. The experiments reported in this paper indicate that type-I PM LBO OPOs offer higher efficiency and a broader wavelength tuning range than type-II configurations, whereas type-II PM LBO OPO may be more favorable for achieving narrower spectral linewidths.