Abstract

Sum-frequency mixing between the fundamental and second harmonic of Nd: YAG lasers yields 355-nm-output. However, the normalized nonlinear conversion efficiencies that are typically on the order of 10⁻⁵ to 10⁻³ W⁻¹ severely limit the conversion efficiency in the cw mode, requiring enhancements of the inputs. In the sum-frequency mixing, two inputs at different wavelengths need to be enhanced simultaneously for the enhanced conversion efficiency. We report on generation of 410 mW of 355-nm output by doubly-resonant sum-frequency mixing. In order to simultaneously enhance both inputs, we utilize two independent single-frequency lasers as well as two independent servo loops. The first servo loop locks the mixing cavity to the first laser, while the second loop locks the frequency of the second laser to the external cavity. Double-resonance is achieved when both of the servo loops are closed. Under the double-resonance, enhanced fields are built up in the cavity at both input wavelengths, hence increasing the nonlinear conversion efficiency.

© 1996 Optical Society of America