Luminescent and lasing characteristics of heavily doped Yb3+:KY(WO4)2 crystals

The luminescence decay times are measured taking into account reabsorption for KY(WO₄)₂:Yb(KYW:Yb) crystals with atomic concentrations of active ions from 0.2% to 30%. The radiative lifetime of Yb³⁺ ions was measured to be 233 μs. The cw output power of 1.46 and 1.62 W was achieved with the slope efficiency 52% and 47% for Yb:KYW lasers with the atomic concentration of Yb³⁺ ions equal to 10% and 30%, respectively. Using a semiconductor mirror with a saturable absorber (SESAM) in the passive mode-locking regime, pulses of duration 194 and 180 fs were obtained at wavelengths of 1042 and 1039 nm for crystals with Yb³⁺ concentrations equal to 10% and 30%, respectively, the average output power being 0.63 and 0.75 W.