Single-frequency continuous-wave tunable ultraviolet sources based on BIBO and PPKTP crystals and their comparative studies

We report on development of tunable, cw, single frequency ultraviolet (UV) source based on intra-cavity frequency doubling of an optical parametric oscillator (OPO). The singly resonant OPO (SRO) is realized using 25 mm long MgOdoped periodically poled stoichiometric lithium tantalite (MgO:sPPLT). The SRO, pumped in the green, is intra-cavity frequency doubled using two different crystals β-BaB2O4 (BIBO) and periodically poled KTiOPO4 (PPKTP) to generate tunable UV radiation. The BIBO based source produces UV radiation with output power as much as 770 mW at 398.24 nm in elliptic (0.66) spatial beam while pumping at 8W of green power. The UV source can be tuned across 355.2-418 nm with a continuous wavelength tunability of 62.8 nm in single frequency radiation with instantaneous line-width of 14.5 MHz. On the other hand, the PPKTP based UV source generates maximum UV power of 336 mW at 398.28 nm and wavelength tunability of 18.1 nm in a TEMOO spatial mode with ellipticity of 0.93 for 5W of green pump power. The line-width of the UV radiation is measured to be 18.5 MHZ. In comparison, PPKTP based UV source provides better performance than BIBO in terms of beam quality and power stability.