Growth, spectroscopy and high-power laser operation of Er:YAP crystal with different Er3+ concentrations

Er3+-doped YAP crystals with concentrations of 5 at%, 10 at%, 15 at% and 20 at% were grown successfully by Czochralski method. X-ray rocking curves suggest high crystalline quality. Lifetime ratio of I-4(13/2) and I-4(11/2) levels decreases obviously with the increase of Er3+ concentrations, which is beneficial to realize population inversion and decrease the laser threshold. Spectroscopy and laser show the 15 at% Er:YAP crystal has strongest mid -infrared fluorescence intensity and best laser performance by 968-nm LD side-pumping. Maximum average powers of 23.52 and 11.08 W are achieved at 250 and 1000 Hz, corresponding to the slope efficiency of 12.0% and 6.2%, respectively. Therefore, the 15 at% Er:YAP crystal is a promising candidate for the high-power and high-frequency mid-infrared laser.