INFRARED UP-CONVERSION WITH BETA-BARIUM BORATE CRYSTAL

Abstract

An IR up-conversion with a beta barium borate (beta-BBO) crystal as an upconverter has been made. The IR source at wavelengths 2.45-mu-m and 2.69-mu-m was provided by the lithium vapor excited by a pulsed dye laser tuned to the 2S-4S two-photon resonance of lithium atom. The phase matching angles for the type I phase matching has been measured and compared with the calculated values. Based on this comparison, the accuracy of various refractive index formulae extrapolated to the IR region is discussed. The IR up-conversion efficiency has also been measured which agrees reasonably with the calculation under a plane-wave approximation. The up-conversion with the beta-BBO crystal provides an effective approach for the IR detection in the 1-3-mu-m wavelength region.