The Czochalski Growth Of Yb-doped New Laser Crystal

Yb3+ ion-doped laser crystals have aroused much interest with the development of high-power laser diode pump source whose emission wavelength is between 0.9-1.1μm. As the activation ion with the simplest energy levels, Yb3+ has some superior characters over Nd3+, which make it more beneficial to the miniaturization of solid laser devices. This thesis reports the growth, spectroscopic and lasing properties of Yb3+: (Sr1-xCax)3Gd(BO3)3 and Er3+/Yb3+: Sr3Gd(BO3)3 crystal.The Yb3+: (Sr0.9Ca0.1)3Gd(BO3)3, Yb3+: (Sr0.8Ca0.2)3Gd(BO3)3, Yb3+: (Sr0.7Ca0.3)3Gd(BO3)3, Er3+/Yb3+: Sr3Gd(BO3)3 crystals were grown by Czochalski Growth. The Yb3+: (Sr0.9Ca0.1)3Gd(BO3)3, Yb3+: (Sr0.8Ca0.2)3Gd(BO3)3, Yb3+: (Sr0.7Ca0.3)3Gd(BO3)3 crystals are crack, because of the faster cooling rate.The pink Er3+/Yb3+: Sr3Gd(BO3)3 crystal is crack free. The concentration of Yb ion in Yb3+: (Sr0.9Ca0.1)3Gd(BO3)3 crystal and the concentration of Yb and Er ions in Er3+/Yb3+: Sr3Gd(BO3)3 crystal were measured using ICP-AES means. The segregation coefficient of Yb ion in Yb3+: (Sr0.9Ca0.1)3Gd(BO3)3 crystal is 0.951. The segregation coefficient of Yb ion and Er ion in Yb3+: (Sr0.9Ca0.1)3Gd(BO3)3 crystal are 0.977, 0.99, respectively. The absorption spectra, fluorescence spectra and fluorescence lifetime of Yb3+: (Sr0.9Ca0.1)3 Gd(BO3)3, Yb3+: (Sr0.8Ca0.2)3Gd(BO3)3, Yb3+: (Sr0.7Ca0.3)3Gd(BO3)3 crystals were measured at room temperature. The spectroscopic and lasing properties of Yb3+: (Sr0.8Ca0.2)3Gd(BO3)3 crystal are best. The strongest absorption is centered at 975nm wavelength. Theσ-polarized andπ-polarized absorption cross-section are equal to 2.53×10-21cm2, 3.55×10-21cm2 at 975nm, respectively. Theπ-polarized absorption transition at 975nm has an FWHM of 9nm. Theπ-polarized emission cross-section is equal to 2.30×10-21cm2 at 1012nm. Fluorescence lifetime is 2.12ms. The minimum inversion fractionβmin, the pump saturation intensity Isat and the minimum pump intensity Imin are equal to 4.5%, 27.2kW/cm2, 1.22kW/cm2, respectively.The absorption spectra, fluorescence spectra and fluorescence lifetime of Er3+/Yb3+: Sr3Gd(BO3)3 crystal were measured at room temperature. The absorption band observed in the 850-1050nm is due to both Er3+ and Yb3+, where the absorption band due to the transition 4I15/2 - 4I11/2 in Er3+ overlaps with the absorption band due to the transition 2F7/2-2F5/2 in Yb3+. The absorption cross sectionσa is 4.85×10-21cm2 at 975nm for theσ-polarization and 4.34×10-21cm2 at 975nm for theπ-polarization, respectively. The FWHM ofσ-polarized andπ-polarized absorption transitions at 975nm are 14nm and 12nm, which are suitable for diode pumping, respectively. The strong emission band was observed at 1500-1600nm, which corresponding to 4I13/2-4I15/2 transition of Er3+.