Tm3+ and Ho3+ colasing in in-band pumped waveguides fabricated by femtosecond laser writing

[EN]We report on the first, to the best of our knowledge, in-band pumped Tm3+,Ho3+ codoped waveguide (WG) laser. A depressed-index surface channel WG (type III) with a 50 µm 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 ∼1942nm(Tm3+) and 2059 nm (Ho3+) is 448 mW with a slope efficiencyM of 40.6%, which is a record high for this type of WG lasers. The maximum output power of the Ho laser reaches 144 mWRegional Council of Normandie (NovaMat); European Regional Development Fund (European Regional Development Fund, ERDF); AgenceNationale de la Recherche (LABEX-EMC3); Ministry of Science and Higher Education of the Russian Federation (Goszadanie 2019-1080); Consejería de Educación, Junta de Castilla y León (SA287P18); Agència de Gestió d’Ajuts Universitaris i de Recerca (2017SGR755); Ministerio de Economía y Competitividad (FIS2017-87970-R, MAT2016-75716-C2-1-R (AEI/FEDERUE))