Generation of high-average-power ultrabroad-band infrared pulses

This paper summarizes the results of analytical and numerical studies on a novel technique that is capable of providing high average power ultra broadband radiation that extends from approximately 2 to 16 μm. Such a spectrum has several potential applications, including telecommunications and remote sensing. Additional attractive features of the new source are its anticipated compact size, light weight, ruggedness, and affordable cost. The technique is based on the interaction of a beat wave with a nonlinear medium. The beat wave is formed from the mixing of two CO₂ laser beams with closely spaced wavelengths, such as 9.5 and 9.6 μm. The discrete ultrabroad-band spectrum is generated in a nonlinear optical medium by the self-phase modulation process, a third-order nonlinearity. The long-wavelength portion of the spectrum, i.e., from 5 to 16 μm is produced directly from the interaction of the beat wave with a GaAs crystal. The short-wavelength portion of the spectrum is produced from the interaction of a frequency-doubled beat wave with a GaAs crystal following the chirping of the pulse by a different GaAs crystal and its subsequent optimal compression by a thin sapphire slab