Tm3+ And And Ho3+ Colasing In In-Band Pumped Waveguides Fabricated By Femtosecond Laser Writing

We report on the first, to the best of our knowledge, in-band pumped Tm3+, Ho3+ codoped waveguide (WC) laser. A depressed-index surface channel WC (type III) with a 50 mu m half-ring cladding is fabricated in a 5 at. % Tm3+, 0.5 at. % Ho3+: KLu(WO4)(2) crystal by femtosecond pulse direct laser writing. Under in-band pumping by a 1679 nm Er Raman fiber laser, Tm3+ and Ho3+ colasing is observed in the WG and explained by bidirectional energy transfer. The maximum total output power at similar to 1942 nm (Tm3+) and 2059 nm (Ho 3 +) is 448 mW with a slope efficiencyM of 40.6%, which is a record high for this type of WC lasers. The maximum output power of the Ho laser reaches 144 mW. (C) 2020 Optical Society of America