Efficient frequency upconversion of coherent radiation from 10.26 to 1.187 μm in a GaSe crystal

Frequency upconversion of laser pulses at 10.26 μm to those at 1.187 μm was achieved in the presence of Nd:YAG laser pulses based on difference-frequency generation in a 10 mm-long GaSe crystal. The highest power conversion efficiency for the parametric conversion was determined to be 20.9%, corresponding to the photon conversion efficiency of 2.42%. This value is two orders of magnitude higher than the highest value reported on GaSe in the literature. The saturation of the output power at 1.187 μm as the input power at 10.26 μm was increased, due to the back conversion, i.e. 1.187 μm + 10.26 μm → 1.064 μm, was clearly evidenced. Such a parametric process has potential for achieving sensitive detections of mid-infrared radiation.