Abstract

Sum-frequency generation (SFG) in a nonlinear crystal is a simple and efficient method even for frequency upconversion of cw coherent radiation, but in the wavelength range below 200 nm there are few reports so far.¹ We have already confirmed the generation of cw coherent radiation down to 190.8 nm in a β-BaB₂O₄ (BBO) crystal.² In that experiment the fundamental beams were simply combined in the crystal outside the cavity. Therefore, the output power was limited to tens of nanowatts. Then, we tried to increase the output power using an external enhancement cavity and the walk-off- compensated configuration of the crystals.

© 1992 Optical Society of America