Spectral and Laser Properties of Er3+-Doped CaYAlO4 Crystals
Er3+-doped CaYAlO4 crystals with the doping concentration(atomic fraction)of 15％and 30％were successfully grown by Czochralski method.The polarized spectral and laser properties of Er∶CaYAlO4 crystals were studied.The polarized absorption spectra,polarized emission spectra and fluorescence decay curves were measured at room temperature.The disorder of CaYAlO4 crystal results in broadband characteristics of absorption and emission spectra.The emission cross section of 15％Er∶CaYAlO4 is determined to be 1.22 x 10-20 cm2 at 2 712 nm for σ polarization and 0.71 x10-20 cm2 at 2 754 nm for πpolarization,with a full width at half maximum(FWHM)of 152 and 167 nm,respectively.As Er3+concentration increases,fluorescence lifetime of 4I11/2 and 4I13/2 energy levels decreases in different degrees,and lifetime ratio(τlower/τupper)greatly reduces.The energy transfer upconversion ETU1 not only suppresses self-termination effect but also improves quantum efficiency of 2.7 μm radiative transition.Under 974 nm LD excitation,laser property for output couple mirror with a transmittance of 1.5％is best.The maximum output power is 358 mW at 2 720 nm with a slope efficiency of 15.4％in c-cut 15％Er∶CaYAlO4 crystal.
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