MHz-repetition rate fs-laser-inscribed crystalline waveguide lasers inscribed at 100 mm/s

We report on fast direct laser inscription of waveguide laser structures in a crystal. For the first time, a 1 MHz-repetition rate fs-laser was utilized for this purpose. We inscribed and characterized more than 100 tracks with different inscription parameters in Yb:CALGO crystals. Waveguide lasing with slope efficiencies of up to 57% at a maximum output power of 3.4 W and more than 55% of optical efficiency was obtained under pumping with an optically pumped semiconductor laser (OPSL), even in waveguides fabricated at record-high inscription velocities of 100 mm/s. Such laser performance is similar to previously reported waveguide lasers inscribed at 1 kHz repetition rate and paves the way toward an industrial fabrication of such waveguides.