Gallium selenide has been used as a frequency doubler for the output of a high-power, short-pulse, mid-infrared free-electron laser. Internal conversion efficiencies up to 36% have been achieved in the wavelength range from 6.3 to 12 µm. The second-harmonic output was stable over many hours at peak power levels of 1–2 MW.
© 1996 Optical Society of America
J. M. Auerhammer and E. R. Eliel, "Frequency doubling of mid-infrared radiation in gallium selenide," Opt. Lett. 21, 773-775 (1996)