MHz repetition rate femtosecond radially polarized vortex laser direct writing Yb:CaF waveguide laser operating in continuous-wave and pulsed regimes.

In this paper, we report the use of femtosecond radially polarized vortex laser with MHz repetition rate for direct writing of cladding waveguides (WGs) and realization of waveguide laser oscillations in ytterbium-doped calcium fluoride crystal. The negative refractive index modification in Yb:CaF crystal is fabricated by the homemade all-fiber laser amplifier. At 976 nm pump wavelength, these Yb:CaF WGs can achieve continuous-wave (CW) laser oscillation.