Abstract

Waveguide architecture is attractive for solid-state laser mode locking with a fundamental repetition rate greater than 1 GHz because of its insensitivity to thermal lens in the active medium and availability to monolith constructions of the entire laser source. Here we report on stable continuous passive mode locking at 1064 nm obtained in a compact depressed cladding waveguide, inscribed in the Nd:YAG crystal by the femtosecond laser beam [1]. A linear optical cavity consisted of a multimode waveguide with a core diameter of 110 µm and a length of 6.7 mm, a flat output coupler with 2% transmission at 1064 nm and a flat high-reflection coated at 1064 nm (>99.8%) and high-transmission coated at 808 nm end-mirror. The active medium was pumped through the end mirror by a multimode fibre-coupled laser diode at a wavelength of 809 nm. Mirrors were installed close to the ends of the waveguide on individual 2-adjuster kinematic mirror mounts that allowed tuning the cavity on a single transverse mode. The crystal had a broadband dielectric antireflection coating on the pumping end, and there was no any coating at the crystal end on the output coupler side. The output coupler mount was set at piezo nano-translation stage, which allowed to adjust the gap between the end of the waveguide and the output coupler, forming Gires-Tournois interferometer that allowed controlling the group velocity dispersion in the resonator β₂.

© 2015 IEEE