Abstract
Phase‐matched nonlinear generation of the second harmonic of visible laser sources has been limited to wavelengths longer than about 230 nm because the dispersion of available materials with high ultraviolet transmission cannot be compensated by their birefringence. Parametric upconversion of uv in the range 250–325 nm to the 200–235‐nm band by mixing with a strong infrared signal can be accomplished with 90° phase matching in 45° z‐cut crystals of ADP. A particularly useful embodiment of this idea is the upconversion of dye laser second‐harmonic wavelengths by mixing with the 1.064‐μm output of the Nd:YAG laser. Preliminary experiments in upconverting 266‐nm light to 213 nm have demonstrated stable conversion efficiencies above 50% for this process with peak and average powers above 5 kW and 0.5 mW, respectively.