QUASI-Three-Level Laser Emissions of Neodymium-Doped Disordered Crystal Waveguides

This paper reports on the quasi-three-level continuous wave laser operation based on waveguide structures in neodymium-doped calcium niobium gallium garnet disordered crystal. Laser wavelength selection through the waveguide cross section was observed. Waveguide structures with different cross sections were fabricated by the ultrafast laser inscription, which have propagation losses around 1 dB/cm. With suitable pumping conditions, laser emissions were observed at the low wavelengths of ~930 and ~890 nm. The lasing threshold for the low-wavelength emission was around 50 mW, which is far below the threshold of several watts reported in the bulk laser system. In addition, it was found that the laser generation at the wavelength of ~890 nm has direct relationship with the volume of the waveguide structure. The results suggest advantages of the waveguide platforms over the bulk systems on the low-wavelength laser emission.