Single-frequency operation of a Cr:YAG laser from 1332 to 1554 nm

We report the first demonstration to our knowledge of broadly tunable, single-frequency operation of a cw Cr:YAG laser. Single-frequency operation was obtained from 1332 to 1554 nm with a maximum output power of 680 mW generated at 1457 nm with 10% conversion efficiency of 1047-nm pump laser radiation. A traveling-wave ring resonator was forced to operate unidirectionally by use of Faraday rotation in the Cr:YAG gain medium with a nonplanar resonator alignment, providing the required compensating polarization rotation. Tuning was accomplished with a single-plate birefringent tuning element, and single-longitudinal-mode operation was obtained by the addition of a 9.5-mm-thick uncoated CaF2 etalon. An instrument-limited single-frequency linewidth of 2.3 MHz was measured.