Acousto-optically Q-switched Er:YAP laser emitting at 2.8μm

The free-running and acousto-optically Q-switched laser properties of Er:YAP crystal, which is appropriate for generation at 2.8 μm, are presented. The sample of Er:YAP (concentration 5 at.% of Er3+, thickness 9 mm) had plan-parallel polished faces without antireflection coatings. The excitation of Er:YAP crystal was carried out by a laser diode emitting at 973 nm and working in a pulsed regime (pulse duration 5 ms, repetition rate 10 Hz). The laser resonator was hemispherical, 150 mm in length, with a flat pumping mirror (HR @ 2.8 μm) and a spherical output coupler (r = 150 mm, R = 95 % @ 2.5 - 2.9 μm). In the free-running laser regime, the maximum output power of 156 mW and slope efficiency of 17 % with respect to absorbed pumped power were obtained. To obtain a Q-switching laser operation, the acousto-optic germanium element was inserted between the Er:YAP crystal and the output coupler. The shortest pulse duration of 36.2 ns with a repetition rate of 10 Hz and maximum pulse energy of 0.43 μJ were obtained. The emitted laser wavelength of 2.8 μm can be used as a pump source at room-temperature for Fe:ZnSe or in mid-infrared spectroscopy.