Sum-frequency mixing of CO_2 and He–Ne lasers in proustite

The first known demonstration of efficient sum-frequency mixing of a CO(2) and a He-Ne laser in 77-K cooled proustite is reported. A power-conversion efficiency comparable with that of difference-frequency mixing is obtained. The excellent signal-to-noise ratio of the Fabry-Perot fringes that are obtained leads to the feasibility of wavelength measurement of a stabilized CO(2) laser by a sum-mixing technique, which can complement the conventional difference-mixing technique.