Laser performances of diode pumped Yb:Lu2O3 transparent ceramic at cryogenic temperatures

Abstract

Continuous wave (CW) laser performances of 1 at.% Yb:Lu2O3 sesquioxide ceramic medium were studied under various cryogenic temperatures. Two different fiber coupled diode pump sources, one emitting around 975.7 nm volume Bragg grating (VBG) stabilized and another around 940 nm were used for comparison. Under the pump at 975.7 nm and 100 K cryogenic temperature, the laser yielded CW output power of 11.24 W for 20.3 W incident pump power, corresponding to an overall optical-to optical efficiency of 55%; the slope efficiency was 59%. For operation at room temperature, the output power was limited to 4.44 W whereas the slope efficiency was 27.5%. Optimum operation under 940 nm pump was obtained at 80 K. Under 940 nm pumping, Yb:Lu2O3 medium generated a CW output power of 3 W for 20 W; the slope efficiency was around 17%. The passive Q-switch operation was investigated with Cr4+:YAG saturable absorber (SA) crystal, employing the pump at 975.7 nm. Laser pulses with an energy of 0.35 mJ and a pulse duration of 116 ns at 26.1 kHz repetition rate were recorded with a Cr4+:YAG SA having 85% initial transmission.