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A new laser crystal from Lu2.4Y0.6Al5O12 (LuYAG) co-doped with Cr3+, Tm3+, Ho3+, and Pr3+ ions was grown successfully by the Czochralski method for the first time. The structure parameters of the Cr,Tm,Ho,Pr:LuYAG crystal are determined by the X-ray Rietveld refinement method. The main absorption bands are observed near 426 and 782 nm, and the fluorescence spectrum excited by a 450 nm or 783 nm LD presents an emission band near 2.911 μm, indicating that the co-doped Cr3+ and Tm3+ ions can be utilized as sensitizers for the Ho3+ ions. The lifetimes of the 5I6 and 5I7 levels of the Ho3+ ions were measured and fitted to be 0.070 ms and 1.852 ms, respectively. The energy transfer efficiencies of the processes 5I6 (Ho3+) →3F3,4 (Pr3+) and 5I7 (Ho3+) →3F2 (Pr3+) + 3H6 (Pr3+) were calculated, showing that the Pr3+ ions can play the role of a deactivator for the Ho3+ ions. Furthermore, the energy transfer mechanisms among the Cr3+, Tm3+, Ho3+, and Pr3+ ions were studied. The results suggest that the Cr,Tm,Ho,Pr:LuYAG crystal is a new promising laser medium operating at around 2.9 μm under flash lamp or 783 nm LD pumping. [ABSTRACT FROM AUTHOR]

Yb,Ho:YAP and Yb,Ho,Pr:YAP laser crystals with high optical quality are successfully grown using the Czochralski method. The absorption coefficient and band width of the two crystals at 970 nm are increased because of the doping of Yb 3+ sensitizer. The three strongest fluorescence peaks of the two crystals are located at approximately 2844, 2853, and 2912 nm, which correspond to the 5 I 6 → 5 I 7 level transitions of Ho 3+ ions. Lifetime measurements indicate that the deactivator Pr 3+ ions can efficiently decrease the lifetime of the lower level 5 I 7 from 8.848 ms to 1.258 ms. Energy-transfer mechanisms are also studied and analyzed, and up-conversion luminescence spectra provide the further evidence that Pr 3+ ions can efficiently depopulate Ho 3+ ions at the 5 I 7 level. All these results show that Yb,Ho,Pr:YAP crystal may be a promising laser medium for realizing 2.8–3.1 μm lasers pumped using a 970 nm laser diode. [ABSTRACT FROM AUTHOR]

A series of Ho and Pr doped LuYSGG laser crystals were successfully grown by Czochralski method. X-ray rocking curves indicate their high crystalline quality. Crystal structure and basic parameters are provided by XRD and Rietveld refinement. Combining density functional theory, the bandgaps of YSGG and LuYSGG are calculated to be 3.497 and 3.483 eV, respectively. Particularly, the J-O parameters and emission spectra suggest the LuYSGG is more suitable as host for Ho3+ ions and could achieve better 2.9 μm emission than the YSGG. Meanwhile, the luminescent decay curves show the deactivated Pr3+ ion can greatly narrow the lifetime gap between the 5I 6 and 5I 7 energy levels, which can eventually attenuate effect of self-termination phenomenon on the 2.9 μm emission. • A series of Ho and Pr doped LuYSGG mixed laser crystals are prepared. • Microscopic and bandgap structure of LuYSGG are investigated in detail. • LuYSGG is more suitable for achieving Ho:2.9 μm emission than YSGG. • Pr can effectively attenuate the 2.9 μm self-termination phenomenon. [ABSTRACT FROM AUTHOR]

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 4I 13/2 and 4I 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. • High-quality Er:YAP crystals with four concentrations were grown by the Cz method. • Influences of Er3+ concentrations on the performance of Er:YAP crystals were studied. • Energy transfer and luminescence mechanism in the Er:YAP crystals were analyzed. • LD side-pumped high-power and high-frequency Er:YAP laser is demonstrated. • Maximum average power of 23.52 W was obtained on the 15 at% Er:YAP crystal. [ABSTRACT FROM AUTHOR]