Y-branch waveguide splitters inscribed in Nd:KGW crystal by femtosecond laser writing: realization and laser emission

We report on the fabrication of active optical waveguide splitters with circular cladding geometry in Nd:KGW crystals using direct femtosecond laser writing. Y-branch waveguides capable of one to two beam splits were fabricated with a single 60-mu m-diameter straight waveguide as the input end and two 30-mu m-diameter output ends. The full branching angle between the two output arms changed from 1.0 deg to 2.4 deg. Confocal micro-Raman and microphotoluminescence spectra were used to investigate the Y-branch waveguides. Under the action of an optical pump at 806 nm, simultaneous continuous-wave laser oscillation at a wavelength of 1067 nm in both arms of the Y-branch waveguides was achieved. The laser output was spatially multimodal with a power-splitting ratio of 49.7:50.3 between the arms. A maximum laser output power of 106 mW and slope efficiency of 27.3% were achieved in the active Y-branch waveguide splitter with a splitting angle of 1.0 deg. (C) 2022 Society of Photo-Optical Instrumentation Engineers (SPIE)