Progress in the development of a high average power ultra-broadband infrared radiation source

This paper describes numerical and analytical studies on the optimization of the ultra-broadband infrared (IR) source, a novel high average-power device. The main objective of current studies was the reduction of weight, size, and cost of the system by devising a scheme to generate the two closely spaced radiation lines with a single laser driver instead of the two CO₂ transversely excited atmospheric pressure (TEA) lasers envisioned in the initial work. By inducing the modulation instability in nonlinear media, we have obtained as good or better results as in our previous studies but with one of the TEA lasers replaced by a very low-power driver that provides the seed radiation for the excitation of the instability. Even more importantly, we have demonstrated that the second high peak-power TEA laser can be replaced by a compact, light weight, low peak-power driver by focusing the radiation to a tighter spot. The average power of the source is maintained at the previous level by operating at higher duty factor. In the new low-peak-power operating regime, the output spectrum is very similar to that of the high-power regime, provided that the ratio of the peak power to the nonlinear length that scales proportionally to the area of the laser spot remains fixed