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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]

Structure, defects, and spectroscopic properties of a Yb,Ho,Pr:YAlO 3 (Yb,Ho,Pr:YAP) single crystal grown by the Czochralski method were investigated. The effective segregation coefficients of the Yb 3+ , Ho 3+ , and Pr 3+ ions are 1.06, 1.32, and 0.90 in YAP host, respectively. The structural parameters are obtained by the X-ray Rietveld refinement method. A high crystalline quality of the Yb,Ho,Pr:YAP is determined by the X-ray rocking curve. The dislocations of (100), (010), and (001) faces are studied using the chemical etching with the phosphoric acid etchant. The absorption spectra show that there exists strong absorption in the wavelength range of 900–1000 nm, and the fluorescence spectrum excited by 970 nm LD presents that the strongest emission is located at 2853 nm, indicating the Yb 3+ ions can be acted as the sensitizer for the Ho 3+ ions. The level lifetimes indicate that the Pr 3+ ions can play a deactivator role for the Ho 3+ ions. All these results imply that the Yb,Ho,Pr:YAP crystal can be regarded as a promising candidate for realizing 2.8–3.1 μm laser output. [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]

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 Nd3+-doped Y 2.8 ScAl 4.2 O 12 (Nd:YSAG) single crystal was grown successfully via the Czochralski technology. The crystal structure and crystalline quality of the as-grown Nd:YSAG crystal were determined by the X-ray powder diffraction and X-ray rocking curve, respectively. By X-ray fluorescence analysis, the effective segregation coefficient of Nd3+ is calculated to be 0.33 in the YSAG crystal. Using the chemical etching method, the dislocation density on the (111)-crystalline face is obtained to be about 3.45 × 102 cm−2. The large absorption cross-section (2.95 × 10−20 cm2) and wide FWHM (9.8 nm) around 808.8 nm imply a high LD pumping efficiency. The high emission cross-section (3.53 × 10−20 cm2) at 1336.3 nm and long fluorescence lifetime of Nd3+ ions (286.20 μs) are beneficial to realize laser output. Thereby, all the results indicate that the Nd:YSAG crystal is a potentially new gain material pumped by a LD for near-infrared laser at 1336.3 nm. • A Nd3+:Y 2.8 ScAl 4.2 O 12 crystal was grown successfully by the Czochralski method. • Dislocation density on the (111)-crystalline face is obtained to be 3.45 × 102 cm−2. • A large absorption cross-section (2.95 × 10−20 cm2) implies high pumping efficiency. • High emission cross-section (3.53 × 10−20 cm2) is beneficial to realize 1336.3 nm laser. • All results indicate this crystal is a potential gain material for 1336.3 nm laser. [ABSTRACT FROM AUTHOR]

Highlights: [•] The THz absorption spectra of piracetam and its pharmaceutical cocrystals are reported. [•] The cocrystal formation is monitored from both time and frequency-domain THz spectra. [•] THz-TDS is potential to directly characterize the pharmaceutical solid-state reactions. [Copyright &y& Elsevier]

Single crystals of Dy:GdScO3 and Dy,Tb:GdScO3 have been successfully grown by the Czochralski method. High crystalline quality of both crystals was determined via X-ray rocking curves. Effective segregation coefficients of Dy3+ and Tb3+ ions in GdScO3 host were calculated to be ∼0.7 and 1.03, respectively. The large FWHMs and absorption cross-sections of Dy:GdScO3 and Dy,Tb:GdScO3 crystals at 452 nm indicate that they can be efficiently pumped by the commercial blue GaN laser diodes. Both Dy:GdScO3 and Dy,Tb:GdScO3 exhibit relatively large stimulated emission cross-sections at 578 nm and relatively long fluorescence lifetimes. In particular, Dy,Tb:GdScO3 shows an enhanced yellow emission at around 578 nm. The energy transfer between Dy3+ and Tb3+ ions is beneficial for realizing population inversion by depopulating the population of the lower laser level of Dy3+ and has negligible influence on the upper laser level. Additionally, the defects and thermal properties of Dy:GdScO3 were investigated since they are very important for crystal growth and laser applications. Collectively, these results suggest that Dy:GdScO3 and Dy,Tb:GdScO3 can be regarded as promising candidates for realizing 578 nm laser output. [ABSTRACT FROM AUTHOR]