Abstract
Conversion of 10.6‐μm laser radiation into the spectral region of almost optimal photomultiplier performance is realized by nonlinear mixing of the infrared signal with a dye laser. Quantum conversion efficiencies exceeding 40% are obtained. This order‐of‐magnitude improvement of the up‐converter efficiency was achieved with a AgGaS2 crystal of only 5 mm length, because the noncritical collinear 90° type‐I phase‐matching geometry was realized.