Absorption and oscillation characteristics of a pulsed Cr4+:YAG laser investigated by a double-pulse pumping technique

摘要

Because of the low Cr4+ concentration innCr4+: YAG crystals, the output energy of thenCr4+:YAG laser is limited by the ground-state depletion of Crn4+ when pumped by a Q-switched Nd:YAG laser. We propose andndemonstrate a double-pulse pumping technique to improve the output powernand energy, by which a Cr4+ ion that returns to the groundnstate during lasing is repumped by the second pump pulse and cannimmediately contribute to lasing. The output power and energy werenincreased by factors of 5 and 4, respectively, from those innconventional single-pulse pumping. These enhancement factors werenlimited by the relaxation time from the higher excited state followingnexcited-state absorption to the upper laser level. In addition to thenfast relaxation reported so far, we found that there is a slownrelaxation channel with a time constant of approximately 100 ns, whichnwas also explored by using the double-pulse pumping technique