High efficient single-frequency output at 1991 nm from a diode-pumped Tm:YAP coupled cavity

A coupled resonator was developed for high efficient room-temperature single-frequency laser operating near 2 mum optical spectral region. 721 mW stable single-longitudinal-mode oscillation at 1991 nm was obtained when the absorbed pumping power was 2.4 W. The optical-to-optical efficiency was 30%, and the slope efficiency was 46%. 5 nm of frequency tuning range was obtained with stable output power. The beam propagation factors M2 were 1.43 and 1.42 in x and y directions, respectively.