Quasi-continuous wave and continuous wave laser operation of Eu:KGd(WO4)2 crystal on a 5D0 → 7F4 transition

We report on the first demonstration of quasi-continuous wave (quasi-CW) and real CW room-temperature lasing on the D-5(0) -> F-7(4) transition of Eu3+-doped material using a 25 at.% Eu3+ : KGd(WO4)(2) crystal pumped into the F-7(1) -> D-5(1) transition by a diode-end-pumped Nd3+ : KGd(WO4)(2)/KTP green laser at 533.6 nm. The maximum CW output power of this laser at 702.3 nm is 5.3 mW with 1.4% green-to-red conversion efficiency. In quasi-CW operation mode with a 10% duty cycle, the peak power of ms long pulses reaches similar to 54 mW, which corresponds to the optical conversion efficiency of 3.5%.