1.5-microm-band thulium-doped microsphere laser originating from self-terminating transition

Continuous-wave 1.5-microm-band laser is demonstrated in thulium doped tellurite glass microsphere by single laser pumping. 1.9-microm laser from the lower transition (3F4->3H6) of Tm3+ is generated to depopulate the lower level (3F4) of 1.5-microm transition (3H4->3F4) in order to achieve the population inversion. Laser wavelength of 3H4->3F4 transition is shifted by 30 nm from the emission peak. Slope efficiency of 1.9-microm laser is improved after the1.5-ìm laser starts to lase.