Abstract

There is an increasing demand for tunable laser sources in the 8-12 µm spectral range for stand-off detection of chemical traces. In addition to high peak power, fast and wide spectral tunability are required. Among direct sources, external-cavity quantum cascade lasers (EC-QCL) have demonstrated a broad tunability with narrow linewidths and excellent beam quality [1] but their limited peak power restricts the stand-off detection range to a few meters. Orientation patterned GaAs (OP-GaAs) is an excellent nonlinear crystal candidate to reach this wavelength range through a three waves mixing process. A widely tunable pulsed optical parametric oscillator (OPO) was demonstrated [2] at the expense of a complex pump at 3 µm. A narrow linewidth OPO was reported in [3] but the crystal temperature tuning range remains limited and slowly addressed. Recently, we reported on a ~40 W laser system tunable from 7.5 to 9 µm using parametric amplification (OPA) of an EC-QCL and a fast tunable thulium-doped fiber pump [4]. We present here an improved laser system tunable from 8 to 10 µm and delivering up to 140 W peak power thanks to a more robust polarization maintaining pump laser.

© 2017 IEEE