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We investigate the mechanical, thermal properties, and refractive index of (Er0.66Gd1.17)(Pr0.003Y1.167)Sc2Ga3O12 (Er,Pr:GYSGG) crystal with excellent radiation-resistant ability grown by the Czochralski method. The X-ray rocking curve and the optical homogeneity reveal that the Er,Pr:GYSGG crystal possesses high crystalline and optical quality. The crystal density is measured to be 6.03 g cm−3 by the Archimedes method. The Mohr's hardness is obtained to be 6.42, indicating that the Er,Pr:GYSGG crystal is more conducive to being processed compared with Er:YSGG crystal. The thermal specific, thermal conductivity, and thermal expansion coefficient are determined to be 0.52 J g−1 K−1, 5.35 W m−1 K−1, and 8.50 × 10–6 K−1, respectively. The refractive indices corresponding to a few distinct wavelengths are determined by the minimum deviation angle method, which is used to fit the refractive index curve in the range of 320–3000 nm through the Sellmeier dispersion equation. All these results are of great significance for the further research and laser application of the Er,Pr:GYSGG crystal. [ABSTRACT FROM AUTHOR]

Tm3+ doped YAlO3 (Tm:YAP) crystals with different concentrations were grown successfully by Czochralski method. The full width at half maximum of 0.007–0.008° shows high crystalline quality. The shape of dislocation etching pit is consistent with its crystal structure. The absorption spectra show an intensive peak located at 794 nm. The fluorescence lifetimes of 6.06, 4.68, 4.22, 4.01, and 1.93 ms decrease monotonically with the increase of Tm3+ concentration in the range of 2–7.5 at%. The fluorescence spectra exhibit two strong peaks appeared near 1775 and 1853 nm, respectively. Among them, the 4 at.% Tm:YAP crystal possesses the largest fluorescence intensity at 1853 nm, indicating that it is a promising gain material operated at ~ 1.9 μm for the development of diode-pumped solid-state lasers and the dopant concentration larger than 4 at.% may cause decline in laser performance owing to larger reabsorption loss and higher nonradiative decay rate. [ABSTRACT FROM AUTHOR]

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]

A novel Yb,Ho,Pr:LuYAG laser crystal was successfully grown and investigated in detail, which belongs to the cubic system with a space group of I a-3d. The X-ray rocking curve of the as-grown crystal implied high crystalline quality. The dislocation defects were revealed by the chemical method. Moreover, the density, thermal expansion coefficient and thermal conductivity were determined. The absorption coefficient at 935 nm and the emission cross-section at 2.911 μm were obtained to be about 15.18 cm−1 and 2.23 × 10−21 cm2, respectively. The lifetime of the lower laser level 5I 7 was shown to decrease from 7.58 to 5.88 ms, while that of the upper laser level 5I 6 basically remained unchanged, suggesting that the co-doped Pr3+ possessed an efficient deactivation effect and was beneficial in attaining population inversions of Ho3+. The corresponding findings illustrate that the Yb,Ho,Pr:LuYAG crystal can serve as a novel promising gain medium for realizing the 2.911 μm laser pumped by ~ 940 nm high-power InGaAs laser diode. • A novel Yb,Ho,Pr:LuYAG laser crystal was successfully grown by Czochralski method. • The crystal possesses a high thermal conductivity, which is helpful in dissipating heat during laser action. • Yb3+ makes the crystal suitable for 935 nm LD pumping and Pr3+ can inhibit self-termination phenomenon. • High absorption coefficient at 935 nm and large emission cross-section at 2911 nm are beneficial in realizing ∼2.9 μm laser. • The Yb,Ho,Pr:LuYAG crystal is a new promising gain medium for realizing 2.911 μm laser. [ABSTRACT FROM AUTHOR]

We demonstrate the performance of a 968-nm laser-diode (LD) side-pumped Er,Pr:YAP laser in free-running and electro-optical (EO) Q-switched modes with emission at 2.7 μm, respectively. In the free-running mode, a maximum power of 11 W is achieved at a working frequency of 150 Hz and a pulse width of 200 μs, corresponding to the single pulse output energy of 73.3 mJ and slope efficiency of 13.3%. In the EO Q-switching mode, a giant pulse laser is obtained with pulse energy of 20.5 mJ, pulse width of 61.4 ns, and peak power of 0.33 MW at the highest working frequency of 150 Hz, corresponding to the energy extraction efficiency of 71.4%. In addition, dual-wavelength laser at 2713 and 2732 nm and beam quality factors Mx2/My2 of 6.62/6.66 are measured, respectively. The results indicate that a 2.7-μm laser with a high repetition rate and high peak power can be realized through LD side-pumped and EO Q-switched Er,Pr:YAP crystal. [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]

We demonstrate the influence of gamma-ray irradiation on the propagation loss and laser performance of an Er,Pr:GYSGG single crystal fiber (SCF). The size of SCF is Φ 0.75 mm × 70 mm and the diameter fluctuation is less than ±3.5%. The propagation loss coefficients of the samples are 0.07 and 0.09 dB cm−1 before and after irradiation, respectively, which is almost unaffected. The maximum output powers of 197 and 192 mW on the SCFs before and after irradiation are obtained under a 969 nm laser diode (LD) end-pumping, corresponding to the slope efficiencies of 8.1% and 7.9%, respectively. A very good beam quality factor M x 2 / M y 2 of 1.11/1.13 is achieved. These results imply that the Er,Pr:GYSGG SCF laser can be used as a potential seed source for mid-infrared (MIR) multi-stage amplification laser apparatus applied in radiation environment. • Er,Pr:GYSGG single crystal fiber (SCF) with a diameter of Ф 0.75 mm is prepared. • Effect of 100 Mrad 60Co gamma-ray irradiation on Er,Pr:GYSGG SCF is demonstrated. • Output power of 192 mW and M x 2 / M y 2 of 1.11/1.13 are achieved after irradiation. • Both maximum output power and slope efficiency are reduced by only 2.5%. • Er,Pr:GYSGG SCF laser is a potential seed light source applied in radiation environment. [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]

We investigate the defect, mechanical, thermal properties, and refractive index of Er:LuYSGG mixed crystal grown by the Czochralski method. The chemical etching pit patterns present a regular tetrahedron, which consists well with the corresponding atomic arrangement schematics. The Mohs hardness is obtained to be 6.60. The thermal expansion coefficient and the thermal conductivity along <111> crystallographic orientation are achieved to be 7.91 × 10−6 K−1 and 3.423 W m−1 K−1, respectively, indicating the Er:LuYSGG has a relatively high damage threshold. Based on the measured values of refractive index, the Sellmeier equation is fitted and the refractive index curve in the range of 400–3000 nm is displayed. All these results are of great significance for the further research and laser application of Er:LuYSGG crystal. • Physical and chemical properties of Er:LuYSGG laser crystal are investigated in detail. • Mohs hardness and thermal expansion coefficient are obtained to be 6.60 and 7.91 × 10−6 K−1. • A high thermal conductivity of 3.423 W m−1 K−1 is conducive to heat dissipation. • Sellmeier equation and refractive index curve are fitted using the measured values. • Results can provide useful parameters for laser application of Er:LuYSGG crystal. [ABSTRACT FROM AUTHOR]

Highlights • Four Cr,Er:YSGG crystal were processed with the size of Ø 3–6 mm × 105 mm. • A maximum pulse energy 1261 mJ operated at 5 Hz and 2.79 μm. • The formula of the thermal focal length is modified further. • Simulation results of the thermal focal lengths consist with the experiments well. Abstract We demonstrate the laser and thermal properties on the four Cr,Er:YSGG crystal rods with different diameters from 3 to 6 mm. A maximum pulse energy 1261 mJ operated at 5 Hz and 2.79 μm is obtained on the rod of 4 mm diameter, corresponding to electrical-to-optical efficiency of 1.53% and slope efficiency 1.82%, respectively. Combining with the electrical-to-optical efficiency and thermal distribution, the formula of the thermal focal length is modified further. The simulation results of the thermal focal length for four crystals with different diameters are in good consistence with the measurement values, suggesting the revised formula is accurate and effective to calculate the thermal focal length. [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]