Growth And Porperties Characterization Of Cr⁴⁺:Ca₂GeO₄ Laser Crystal

The development of the Cr⁴⁺-doped crystals and successful working of pertinent lasersextend the tune of solid tunable lasers from 0.7μm～1.0μm generated by Cr³⁺ and Ti³⁺ ionsto 1.0μm～1.8μm ,and this includes many important wave range, such as eye-safe band,zero-loss and zero dispersion-band of optical fiber and optical communication bands,so thestudy of them has become the hot pot of the study of solid tunable lasers.In the paper, Cr⁴⁺:Ca₂GeO₄ crystal was grown the first successfully by spontaneouscrystallization and flow growth in the country. At the same time, in order to avoid the solutesegregation for the volatilization of GeO₂ and reduce the probability of Ca₃Ge₂O₇ impuritiesor other impurities in the crystal grown process, pollycrystallins were synthesized byhigh-temperature solid-phase. The formation mechanism of Cr⁴⁺ion was discussed in thepaper. TG-DSC, XRD, IR, XPS, Raman spectra, and spectral analysis have been used tostudy structureand spectral properties of pollycrstallins and crystal.The XRD results showed that Cr⁴⁺:Ca₂GeO₄ pollycrstallins was obtained at 1300℃by theHigh-temperture solid-phase method. The lattice parameters are a=5.2343(?), b=6.7901(?),c=11.3830(?) Crystal particle size was about 200nm-900nm, the degree of crystallinity was87.96%. Raman spectra demonstrated that polycrystalline induced (GeO₄)^4-. The IR and XPSanalysis results showed that polycrystalline contained Cr₂O₃. The XPS analysis results alsoshowed that polycrystallins had Cr⁴⁺ ions. The different concentration of Cr⁴⁺:Ca₂GeO₄pollycrstallins was synthesized. The Optimum doped -concentration of Cr⁴⁺ ions was 0.5wt%by fluorescence extraction spectra of Cr⁴⁺:Ca₂GeO₄ pollycrstallins.XRD, Absorption and fluorescence spectra of Cr⁴⁺:Ca₂GeO₄ crystal, which was grown bythe spontaneous crystallization and flux growth, were studied. The XRD results showed thatCr⁴⁺:Ca₂GeO₄ crystal was obtained, and lattice parameters were calculated. The absorptionbands between 600nm and 800nm attributed to the Cr⁴⁺: ³A₂→³T₁ level transition, the weaknear infrared absorption band of Cr⁴⁺:Ca₂GeO₄ crystal is due to Cr⁴⁺: ³A₂→³T₂ leveltransition. The strongest fluorescence emission peak of 0.5wt%Cr⁴⁺:Ca₂GeO₄ at the roomtemperature is at 1317nm, which due to Cr⁴⁺: ³T₂→³A₂ transition. The fluorescence lifetimeand emission cross-section of Cr⁴⁺:Ca₂GeO₄ crystal is 7.9μs and 4.61×10^-19cm², respectively.