Femtosecond laser written continuous-wave Nd³⁺:BaY₂F₈ waveguide laser at 1.3 μm

We experimentally demonstrate, for the first time to our knowledge, robust operation of a Nd³⁺:BaY₂F₈ waveguide laser at 1.3 μm without any parasitic lasing at any other wavelength. The best power performance was obtained with a depressed cladding waveguide, having a diameter of 70 μm, which was fabricated by employing femtosecond laser writing. The propagation loss of the waveguide was measured as 0.33 dB/cm at the wavelength of 761 nm. The power performance of the waveguide laser was investigated for E//z and E//y pumping polarizations by using butt-coupled flat resonator mirrors. Higher power performance was obtained for E//z pumping, where the resonator with the 6.2% transmitting output coupler produced 157 mW of continuous-wave output power at 1318 nm with 882 mW of pump power at 800 nm. The measured power slope efficiency was 19% with respect to the incident pump power. By using a different set of cavity optics, 1050-nm lasing performance was also studied, where E//z pumping at 800 nm with the 12% transmitting output coupler yielded 307 mW of output power with 31% slope efficiency. Use of a host medium with relatively low refractive index around 1.5 was instrumental in reducing the facet reflectivity and eliminating the possibility of parasitic lasing at 1.05 μm during 1.3-μm lasing.