Many scientific and military applications require pulsed laser sources with high peak power output which are tunable throughout the midwave infrared (mid-IR) spectral region. In this report we discuss the design, construction, and characterization of a gain-switched chromium-doped zinc selenide (Cr:ZnSe) amplifier pumped by a Q-switched holmium-doped yttrium aluminum garnate (Ho:YAG) laser and seeded by a free running continuous wave (CW) Cr:ZnSe laser.
The amplifier pump laser was constructed using a 0.5% Ho-doped, Brewster-cut YAG rod. In CW operation, powers of up to 3.68 W and a slope efficiency of 45% were obtained. In pulsed operation at 1 kHz pulse repetition frequency (PRF), pulse energies of 2.6 mJ per pulse were obtained with temporal pulse widths less than 100 ns. The output wavelength of the pump was 2.1 μm with a spectral width less than 1 nm.
The pulsed Ho:YAG laser was then used to gain-switch a Cr:ZnSe single-pass pulsed amplifier seeded with a CW Cr:ZnSe laser with a free-running wavelength of 2.4 μm and a spectral linewidth of 50 nm. The output of the gain-switched amplifier yields a pulsed beam at the seed wavelength demonstrating high gain. By design, this source will follow the lasing wavelength of the seed beam allowing for tunability over the entire emission wavelength of Cr:ZnSe with proper seed design. The end result of this work was a versatile, pulsed mid-IR source.