Femtosecond-laser-written Ho:KGd(WO 4 ) 2 waveguide laser at 2.1  μm.

We report on efficient laser operation of the first holmium monoclinic double tungstate waveguide laser fabricated by femtosecond direct laser writing. A depressed-index buried channel waveguide with a 60 mu m diameter circular cladding was inscribed in 5 at.% Ho3+:KGd(WO4)(2). It was characterized by confocal microscopy and mu-Raman and mu-luminescence spectroscopy, indicating well-preserved crystallinity of its core. Pumped by a thulium bulk laser, the holmium waveguide laser generated 212 mW at 2055 nm with a slope efficiency of 67.2%. The waveguide propagation losses were 0.94 +/- 0.2 dB/cm. (C) 2019 Optical Society of America