Short-pulsed gain-switched Cr²⁺:ZnSe laser

We report the first demonstration of gain-switched, ultra-low-threshold Cr²⁺:ZnSe laser generating pulses as short as 1.75 ns. A diode pumped Tm³⁺:YLF laser delivering up to 5 mJ energy in 11 ns pulses was utilized as a pump source. The laser operated at 20 Hz repetition rate with 0.1 duty factor allowing us to reduce thermal effects in an active crystal. In a short resonator (length, 70 mm) we obtained more than 0.5 mJ of output energy and 300 kW of corresponding peak power. The Cr²⁺:ZnSe laser was characterized by very low losses manifesting themselves by an extremely low generation threshold of less than 7 μJ and very high slope efficiency (reaching the quantum efficiency) determined with respect to absorbed pump power. (letter)