Radiation source based on an optical parametric oscillator with MgO : PPLN crystal and volume Bragg grating, tunable in ranges of 2050–2117 and 2140–2208 nm

A tunable radiation source based on an optical parametric oscillator (OPO) with a periodically poled lithium niobate (PPLN), generating light with a wavelength of ~2.1 mm in a neardegenerate regime, is developed. The use of a volume Bragg grating (VBG) as a selective element makes it possible to reduce significantly (by a factor of more than 180) the radiation linewidth. Wavelength tuning from 2050 to 2117 nm for the signal wave and from 2140 to 2208 nm for the idler wave is demonstrated. The maximum average OPO output power is found to be 617 mW (123 μJ), which corresponds to a conversion efficiency of 10%. The use of a VBG provides a fundamental possibility of designing a pump source with a small linewidth (of no more than 1 nm) and smooth wavelength tuning in a desired range for frequency converters based on non-oxide nonlinear crystals generating mid-IR light (5–15 μm).