Engineering of refractive index and doping level of KY 1-x-y-zGdxLuyYbz(WO 4)2 layers for a cladding-side-pumped channel waveguide laser

The potassium double tungstates KY(WO4)2, KGd(WO 4)2, and KLu(WO4)2 are excellent host materials for trivalent rare-earth-ion (RE3+) doped solid-state lasers [1] because of their high refractive indices of ∼2.0-2.1 and the large transition cross-sections of optically active RE3+ ions doped into these hosts [2]. Doping of high Yb3+ concentrations results in extremely short absorption lengths down to < 20 μm