Optics, Lasers & Photonics

The 2 μm spectral  range offers the basis for a variety of applications. In some  applications there is importance of high atmospheric transmittance, short pulse duration and high energy per pulse. Commonly, Ho:YAG laser  meets these requirements. But  for this laser ,what is appers in littuter is only short pulses durations with relativly  low energies per pulse for the cavity dumping method or high energies per pulse with longer pulse durations for the Q-switch method. Here we present for the first time a Ho:YAG laser based on gain-switching method that achived both high energy pulses and short pulse duration. The main advantage of using the gain-switch, rather than Q-switching is that a short cavity can be implimented, which is neccecery for obtaining a short pulse duration. In our case the Ho:YAG laser was pumped by a Tm:YLF laser passively Q- switched using Cr:ZeS. The Tm:YLF emision wavelength was tuned to the  Ho:YAG absorption peak. The Ho:YAG cavity was 25 mm long allowing pulse duration of few nsec. For a repetition rate of 500Hz a pulse duration of 3.45ns and maximal energy of 832µJ was achived with pump pulse enrgy of 3.23mJ.  This result corresponding to a slope efficiency of 42.4% and optical to optical conversion of 25.7%. 

The laser emitted at 2090 nm, inside the realevant atmospheric window. The maximal pulse energy and shortest pulse duration were limited by the damage threshold of our laser components