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Highlights • High quality Cr,Er:YAG crystal was grown successfully by the Czochralski method. • Maximum single-pulse energies of 0.99 and 1.52 J are obtained on Er:YAG and Cr,Er:YAG. • Slope efficiencies are 1.31% and 1.80% for Er:YAG and Cr,Er:YAG, respectively. • Cr3+ can improve laser efficiency of Cr,Er:YAG without affecting beam quality. • Cr,Er:YAG may be a potentially mid-infrared radiation-resistant laser material. Abstract We demonstrated an improvement of laser performance by co-doping Cr3+ into Er:YAG crystal grown by the Czochralski method. The result of X-ray rocking curve suggested that the crystal had high crystalline quality. Two strong absorption bands centered at 450 and 596 nm indicated the Cr,Er:YAG crystal was more suitable for xenon lamp pumping. A maximum single pulse energy of 1.52 J was obtained on the Cr,Er:YAG crystal operated at 5 Hz and 2.94 μm, corresponding to the slope efficiency and electrical-to-optical efficiency of 1.80% and 1.28%, but those of the Er:YAG crystal were only 0.99 J, 1.31% and 0.83%, respectively. Therefore, the Cr,Er:YAG crystal may be a potentially mid-infrared radiation-resistant laser material with higher single pulse energy and efficiency. [ABSTRACT FROM AUTHOR]

• Er,Pr:YAP crystals with two different Pr3+ concentrations are grown by CZ method. • Influence of Pr3+ concentrations on the luminescence and laser properties are investigated contrastively. • Watt-level ∼2.7 μm laser is achieved on the Er,0.1Pr:YAP crystal by LD end-pumping. • ∼2.7 μm laser power can be improved by optimizing the concentrations of deactivating Pr3+. High-quality Er,Pr:YAP crystals with two different Pr3+ concentrations are grown successfully, and the spectra and laser performances are studied in contrast. Both two crystals exhibit a wide absorption band with a central wavelength at 972 nm and high transmittance of over 80% in the wavelength range of 2.5 to 5 μm. The luminescence and laser properties are improved when the concentration of Pr3+ decreased from 0.2 at% to 0.1 at%. The maximum powers of 1040 and 835 mW are achieved in the Er,0.1Pr:YAP, and Er,0.2Pr:YAP crystals, corresponding to slope efficiencies of 13.97% and 10.94%, respectively. All the results indicate that co-doping with an appropriate concentration of deactivating Pr3+ is an effective method to attenuate the self-termination effect of Er3+, and then further improve the laser performance. [ABSTRACT FROM AUTHOR]

• Cascade Er:YSGG crystal pulsed lasers near 1.6 and 2.8 μm are realized at room temperature. • The slope efficiency of MIR laser increases to 4.2 % from 1.9 % by cascade process. • Four laser wavelengths of 2.793, 2.821, ∼2.860, 2.917 μm in Er:YSGG laser are discovered. • The cascade process can improve the MIR laser performance based on the Er:YSGG crystal. We demonstrate a pulsed cascade laser on LD end-pumped Er:YSGG crystal near 1.6 and 2.8 μm at room temperature for the first time. The slope efficiency of mid-infrared laser with the assistance of cascade process is significantly improved. Under the working frequency of 100 Hz and pump pulse width of 6 ms, a maximum power of 243 mW centered at 2.79 μm is achieved with increasing slope efficiency of 4.2 %, while the slope efficiency of non-cascade is only 1.9 %. Under high pump power, four laser wavelengths of 2.793, 2.821, ∼2.860, and 2.918 μm are discovered and the phenomenon is explained according to the Boltzmann factors. This work would be conducive to the exploration of pulsed cascade laser based on the Er:YSGG crystal. [ABSTRACT FROM AUTHOR]

• Laser performance of LD side-pumped YSGG/Er:YSGG with concave end-faces is studied. • The laser rods with negative curvature radii of 250, 500 and 1000 mm are employed. • Highest power of 20.92 W with slope efficiency of 26.18% at 150 Hz is achieved. • 15.59 W at 500 Hz is obtained in rod with negative curvature radius of 500 mm. • Thermal bonding and concave end-faces can effectively improve laser performance. We demonstrate the laser performance of 970 nm LD side-pumped YSGG/Er:YSGG/YSGG thermal bonding crystal rods with negative curvature radii of 250, 500, and 1000 mm, respectively. The maximum average output powers of 20.04, 20.92, 17.02 W are achieved, corresponding to the slope efficiencies of 26.28%, 26.18%, 21.28%, and optical–optical efficiencies of 18.56%, 19.37%, 15.76%, respectively. The results of the laser performance and thermal focal length indicate that the negative curvature of 500 mm has an optimal effect on thermal lensing compensation. At the high repetition rate of 500 Hz, the average output power of 15.59 W is obtained. The beam quality factors of M x 2/M y 2 are calculated to be 3.37/3.34. These results can provide valuable references for promoting the development of 2.7–3 μm lasers. [ABSTRACT FROM AUTHOR]

• The 25 at. % Er:YSGG crystal with higher homogeneity was grown by Cz method. • A maximum power of 11.81 W with slope efficiency of 10.49% is realized at 500 Hz. • The laser center wavelength is located at 2794 nm and M2 x /M2 y are 7.01/7.10. • The Er:YSGG rod with concave end faces could be operated at high repetition rate. We demonstrate the laser performance of high repetition frequency on a 970 nm laser diode (LD) side-pumped Er:YSGG crystal rod with concave end faces. The laser performance under different repetition rates and pulse widths was studied with an optimal cavity length. The maximum average output power of 11.81 W operated at a repetition frequency of 500 Hz and 2.794 μm was achieved, corresponding to the slope efficiency of 10.49%. In addition, the beam quality factors M2 x /M2 y of 7.01/7.10 and far-field divergences Θ x /Θ y of 9.15/9.18 mrad were also obtained under the high repetition frequency of 500 Hz. These results show that the LD side-pumped Er:YSGG laser crystal rod with concave end faces has the potential of being operated under high repetition frequency. [ABSTRACT FROM AUTHOR]