An injection-seeded Q-switched Ho: YLF laser by a tunable single-longitudinal-mode Tm, Ho: YLF laser at 2050.96 nm

We proposed an injection-seeded Q-switched Ho: YLF laser by a tunable single-longitudinal-mode Tm, Ho: YLF laser. The tunable single-longitudinal-mode seed laser was achieved by inserting two Fabry-Perot (F-P) etalons in the Tm, Ho: YLF laser resonant cavity and changing the cavity length through a piezoelectric transducer (PZT). The wavelength of single-longitudinal-mode Tm, Ho: YLF laser could be tuned from 2050.962 nm to 2051.000 nm finely. The single-longitudinal-mode output power of 76 mW from Tm, Ho: YLF seed laser was achieved at the CO₂ absorption peak of 2050.967 nm. Single-frequency Q-switched Ho: YLF laser was achieved by injection seeding. The output energy of single-frequency Q-switched Ho: YLF pulse was 4.4 mJ, with a pulse width of 65 ns and a repetition frequency of 100 Hz. The beam quality factor M² of Ho: YLF laser was 1.07, nearly diffraction limit. The full width at half maximum (FWHM) of single-frequency pulse Ho: YLF laser measured by a heterodyne technique was about 4.1 MHz with the simultaneously recorded pulse width of 132 ns.