Growth And Characterization Of Thulium Doped LGSO Crystals

With the rapid development of laser technology,laser is widely used in many fields,such as communication,remote sensing,military affairs,measurement laser microsurgery and precision manufacturing.The performance on laser and ultrafast laser put forward to higher requirements,especially in terms of special bandwidths lasers and ultrafast lasers.Therefore,it is important to research new wavelength and highly efficient ultrafast laser materials for the applications of laser.Based on this background,this paper aims to further broaden the S-band signal optical communication bandwidth and produce 2?m ultrafast lasers,then investigates the spectroscopic properties around 1.4?m and 2?m emissions of thulium ions(Tm³⁺)doped silicate crystal that is suitable for S-band signal and 2?m ultrafast lasers crystal materials and to provide theoretical basis and experimental evidence for 1.4?m and 2?m lasers materials.This paper includes the following five chapters.The first chapter and the second chapter expound the literature review,experimental methods and theoretical basis.The third chapter and fourth chapter are core parts of the paper.The last chapter is the conclusion and outlook.The main contents and achievements of this paper are as follows:1.The research of growth technology of LuGdSiO₅(LGSO),Tm³⁺:LGSO,Tm³⁺/Tb³⁺:LGSO,and Tm³⁺:Lu_0.25Y_0.25Gd_0.5SiO₅(Tm³⁺:LGYSO)crystals.The growth technology of the rare earth ions doped LGSO and LGYSO crystals by the Czochralski method have been systematically researched,including the design of temperature gradient,the selection of growth rate,rotation rate and so on.At last,we have mastered the growth technology of rare earth ions doped LGSO and LGYSO crystals.2.The research of crystal structure,physical and chemical properties.The structures of LGSO and LGYSO crystals were investigated using X-ray diffraction technique,and investigated the change rule of structure in many LGSO micro-crystal with different proportions of lutecium(Lu)and gadolinium(Gd).It's found that as the Lu content is larger than or equal to 30%,the crystal structure of the alloy is C2/c,otherwise it is P2₁/c.3.The research of spectroscopic properties of Tm³⁺:LGSO,and Tm³⁺/Tb³⁺:LGSO crystals.The crystal growth,structure,absorption spectra,Judd-Ofelt parameters,emission spectra and fluorescence lifetime were discussed in details.The results showed that compared with the Tm³⁺-doped LGSO crystal,the Tm³⁺,Tb³⁺-codoped LGSO crystal has a higher fluorescence branching ratio(10.3%),and stronger fluorescence emission intensity corresponding to the 1.4?m emission from Tm³⁺:³F₄?³H₆ transition.It's found that the codoped of Tb³⁺ion in Tm³⁺/Tb³⁺:LGSO crystal greatly depopulates the lower laser level of Tm³⁺:³F₄(from 1.66 ms to 0.38 ms)and has little effect on the upper laser level of Tm³⁺:³H₄ at the same time.The energy transfer efficiency from the Tm³⁺:³F₄ level to the Tb³⁺:⁷F₀level is as high as 77%,indicating that the Tb³⁺ion is an effective deactivation ion for enhancing the 1.4?m emission in Tm³⁺/Tb³⁺:LGSO crystal.These results suggest that Tm³⁺/Tb³⁺:LGSO crystal may be a promising material for 1.4?m laser.4.The research of spectroscopic properties of Tm³⁺:LGSO,and Tm³⁺:LGYSO crystals.The crystal growth,structure,absorption spectra,Judd-Ofelt parameters,emission spectra and fluorescence lifetime were discussed in details.It's found that the absorption cross-section of Tm³⁺:LGYSO is 1.604×10^-20 cm² at 790 nm,which is bigger than other common Tm³⁺doped crystals.The results showed that codoped of Y³⁺ion in Tm³⁺:LGYSO crystal greatly increase the degree of disorder in crystal and broaden emission bandwidth.The results above indicate that Tm³⁺:LGYSO crystal is a promising laser crystal for tunable and ultrafast laser output around the 2?m wavelength.