Line-Tunable Singly Resonant Optical Parametric Oscillator in Mid-Infrared Spectral Range Based on KTA Crystal

Line-tunable narrow-linewidth mid-infrared radiation in 3-5-mum spectral range by singly resonant optical parametric oscillation technique based on a KTA crystal pumped by 1.064-mu m radiation from a Q-switched Nd:YAG laser using different gratings has been demonstrated. Thresholds of oscillation energy at different cavity lengths and at different idler wavelengths with different gratings have been measured. Energy of the generated radiation at 3.6 mum as a function of pump beam energy at different cavity lengths with different gratings have been measured. Maximum energy obtained at 3.6-mum radiation with a grating having grooves density 85 l/mm at 55-mm cavity length is 4.6 mJ when the cavity was pumped by 42.6-mJ energy, which corresponds to conversion efficiency from pump beam energy to generated idler beam energy 10.8% and maximum slope efficiency achieved was 23.6%. The linewidth obtained with a grating having grooves density 600 l/mm at 3.7 mum was 0.53 cm^-1.