Periodic variations of sum-frequency output are observed in upconversion of 10.6 µm radiation from a CO2 laser in a proustite crystal pumped by a Nd:YAG laser beam and concluded to be caused by multiple reflection of infrared wave which occurs inside the nonlinear crystal.

A new optical wavelength demultiplexer using quasi-phase-matched sum-frequency-generation (QPM-SFG) is proposed. The device consists of an optical deflector using Pockels effect and a nonlinear crystal with a periodic structure. The demultiplexing characteristics of the device composed of a LiNbO3 crystal are analyzed theoretically. Wavelength demultiplexing can be made simply by changes in the electric field applied to the deflector.

Two-dimensional acceptance angles of a proustite upconverter operating in several type I phase-match conditions are measured and compared with theoretical ones. They agree reasonably well with each other.