Passively pulsed 800-nm thulium-doped all-silica fiber laser via intracavity pumping

We demonstrate a record-short-wavelength 800.7-nm passively pulsed thulium-doped all-silica fiber laser. The system employs an intracavity pumping scheme based on a 1530-nm passively Q-switched erbium/ytterbium co-doped fiber resonator driven by a CW 976-nm diode. This architecture circumvents rapid nonradiative relaxation in silica, generating single-mode pulses with an energy of 1.9 µJ and a duration of 85 ns at 0.3 MHz. The laser exhibits a pump threshold as low as 6.5 W. Coupled rate equations are developed to elucidate the sequential excited-state absorption and gain-switching dynamics governing this short-wavelength thulium emission.