Influence of multi-line CO laser focusing on broadband sum-frequency generation

摘要

The influence of a multi-line CO laser focusing on spectral characteristics of broadband sum-frequency generation in ZnGeP2 nonlinear crystal was experimentally and numerically studied. Maximal frequency conversion was experimentally observed under a tight focusing laser beam of a multi-line CO laser rather than a single-line one. The tight focusing resulted in a broadening sum-frequency generation spectrum and an increasing total, i.e. integrated over the spectrum, frequency conversion efficiency. These effects were due to the increasing phase-matching bandwidth and angular dispersion. The maximal conversion efficiency of the multi-line CO laser was numerically demonstrated to take place at a focal length of 0.4 times that required for the single-line one.