High-quantum-efficiency infrared up-conversion.

Experimental study in which 100% conversion of infrared photons into visible photons was achieved through three wave interactions in a nonlinear medium. The first experimental evidence of overconversion is presented, and the classical theory of up-conversion in the high-conversion-efficiency region is confirmed. A laser pump light feedback technique is described that promises to make the process practical with modestly powerful pump lasers and less than perfect nonlinear crystals. The nonlinear medium used was a LiIO3 crystal that cannot be 90-deg phase-matched. The 'walk off' that resulted helped make possible the attainment of 100% conversion efficiency.