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 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 the spectral linewidth was ∼23.2<i>n</i><i>m</i>. The temperature tuning range was 3.5°C, corresponding to an average wavelength tuning rate of ∼22<i>n</i><i>m</i>/^∘<i>C</i>. The beam quality factor <i>M</i>² 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 424 mW, achieving an 18.4% conversion efficiency and a spectral linewidth of ∼1.3<i>n</i><i>m</i>. The temperature tuning range was 130°C, corresponding to an average wavelength tuning rate of ∼0.77<i>n</i><i>m</i>/^∘<i>C</i>, and the beam quality factor <i>M</i>² 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 the type-II PM LBO OPO may be more favorable for achieving narrower spectral linewidths.