Switchable and tunable thulium-doped fiber laser incorporating a Sagnac loop mirror

A thulium-doped fiber laser employing a Sagnac loop mirror made by a 145.5 cm polarization-maintaining fiber is demonstrated, which can operate with stable dual-wavelength lasing or tunable single-wavelength lasing around 1860 nm. Both stable dual-wavelength and tunable single-wavelength lasing are achieved by adjusting a polarization controller in the Sagnac loop mirror. The experimental results show that the output of the reported fiber laser with two different operation modes is rather stable at room temperature.