Self-Q-switched and broad wavelength-tunable lasing in Tm3+-doped CaF2 single-crystal fiber

Self-Q-switched lasing was demonstrated for the first time around 2-µm in Thulium (Tm) doped CaF2 single-crystal fiber (SCF) using a compact linear cavity. Maximum average output power of 1.17 W was obtained under 2.38 W absorbed pump power, corresponding to the slope efficiency of up to 56.01%. Self-Q-switched laser with a 1.736 µs shortest pulse width at 48.80 kHz repetition rate was successfully realized. Besides, broad wavelength-tunable Tm:CaF2 SCF laser in 1859-2040 nm region was operated. These results show that the Tm:CaF2 SCF is a promising alternative for generating efficient micro diode-pumped pulsed lasers at 2-µm.