A platform for compact diode-pumped visible lasers: waveguides in rare earth doped fluorides

In this work we present the fabrication of various waveguide lasers fabricated by direct femtosecond laser writing in rare earth doped fluoride single crystals. By fabricating waveguides in Pr:LiLuF4, we observed diode-pumped π-polarized lasing at 604 nm and 721 nm, achieving record power for diode pumped waveguide laser and slope efficiencies comparable to the values observed in Pr-based bulk laser. Moreover, lasing in the green and infrared band were observed, achieving record value for the output power for these lines. In addition, the weaker 645 nm π polarized laser emission was observed, with a maximum output power of 1 mW. The 698 nm line was studied with an external cavity configuration, achieving a record power of 42 mW. In the end, lasing from the cyan line was observed for the first time from a waveguide laser written in PrBa(Y0.8Lu0.2)2F8, delivering a maximum output of 22 mW with slope efficiencies comparable to bulk lasers. To fill the yellow gap, Dy,Tb:LiLuF4 was employed to fabricate the first yellow waveguide laser, achieving output power of about 100 mW and a slope efficiency of 19%, a record among all solid state Dy lasers.