Widely tunable long-wave infrared difference frequency generation with a BaGa₄Se₇ crystal

Abstract

We report an experimental study of long-wave infrared difference frequency generation based on B a G a 4 S e 7 crystal. The sources of two input wavelengths were the fundamental output of a Nd:YAG laser and its second-harmonic pumped ∼ 1.2 µ m K T i O P O 4 optical parametric oscillator. A wide tuning range of 7.9–17.5 µm ( > 1.14 octave) was achieved, which reached the upper limit of the B a G a 4 S e 7 transparency region. The spectra and pulse widths, input–output relationship, beam profile, wavelength tolerance, and angular acceptance of the phase-matching were characterized in detail. This presented coherent source can potentially be applied in multiple gas analyses and spectral imaging.