Collinear 3.3913- and 0.6328-micron laser beams were mixed in LiNbO
3to produce the sum frequency corresponding to 0.5333 microns. The laser beams were generated simultaneously in a single He-Ne laser tube. With incident powers of 4.43 and 2.75 mW at 0.63 and 3.39 microns, respectively,

mW were generated at 0.53 microns. The magnitude of this conversion is in satisfactory agreement with theory. Some of the characteristics of this system when viewed as an infrared detector are also given.