Study Of The Structure And Mid-infrared Emission Properties In Rare-earth Ions Doped Tellurite Glasses

In recent years,the mid-infrared fiber has been reseached extensively and deeply,and this is because the band of optical materials have been widely used both in the field of civilian and military applications.In order to obtain a cheap,practical and efficient medium-infrared laser source,a large number of studies have been carried out on the crystal,ceramic,glass and optical fiber doped with rare earth ion.This paper is to research the gain medium glass material which can be applied to the mid-infrared laser output.Through the double rare earth doped tellurite glass sub strate ion,the mid-infrared fluorescence spectra and energy transfer mechanism between the doped rare earth ions have been studied.Compared to the traditional laser glasses,tellurite glass as heavy metal oxide glass has a lower phonon energy and high index.Besides,it has a lower melting temperature and a better chemical stability.Thus,in this paper,TeO₂-WO₃-ZnO-La₂O₃ tellurite glass system is selected as the matrix.The glass sample is tested by Raman spectroscopy,and it is found to have low phonon energy(the maximum phonon energy is 750 cm^-1).At the same time,through the differential thermal analysis?DTA?,and found that it has a lower energy transition temperature T_g?345??and a larger?35?T?163??.The absorption spectra of doped Dy³⁺and Er³⁺glass samples are further studied,the J-O parameters and radiation properties are discussed respectively.Under the excited by 808 nm laser diode,the fluorescence output of 2.8?m is obtained from Dy³⁺doped glass sample.In addition,under the excited by 808and 980 nm LD,both of the 2.7?m fluorescence output are obtained from Er³⁺doped glass sample.Base on the research,we have further studied the fluorescence spectra properties of 2.7?m and 2.8?m in Dy³⁺/Er³⁺co-doped tellurite glasses under 808 or 980 nm LD.It is found that the broadband mid-infrared emissions are obtained from Dy³⁺/Er³⁺co-doped tellurite whether at an excitation of808 or 980 nm LD.Under 808 nm excitation,the energy transfer efficiency from Er³⁺:⁴I_13/2 to Dy³⁺:⁶H_11/2 level is 73.1%and the energy transfer coefficient of Er³⁺:⁴I_11/2?Dy³⁺:⁶H_5/2 and Er³⁺:⁴I_13/2?Dy³⁺:⁶H_11/2 are6.89×10^-38 and 0.01×10^-38 cm⁶/s,respectively.Under 980 nm excitation,the energy transfer efficiency from Er³⁺:⁴I_13/2 to Dy³⁺:⁶H_11/2 level can reach as high as 80%.In order to further study the³?m luminescence properties of the glass material,the fluorescence spectra of Dy³⁺/Tm³⁺co-doped tellurite glasses with different Tm₂O₃ content under the 808 nm LD excitation have been studied.As the content of Tm₂O₃ increased,the fluorescence intensity of 1.8and 2.3?m decreased continuously in Dy³⁺/Tm³⁺co-doped samples,while the fluorescence intensity of 2.8?m is continuously enhanced.Among them,the stimulated emission cross section of 2.8?m can reach as high as 2.82×10^-20cm² in 0.5mol%Dy³⁺/1.5mol%Tm³⁺co-doped sample.The energy of Tm³⁺:³H₄level can be efficiently transferred to the Dy³⁺:⁶H_11/2 level through energy transfer ET2,the energy transfer rate efficiency is as high as 86.80%.At the same time,the enhancement mechanism of 2.8?m fluorescence has also been discussed.Radiation around²?m is deemed to be safe for the eyes,which can be used for various useful applications including infrared laser guidance and detection,heterodyne coherent detection and high resolution spectral analysis of pressure gas.Therefore,²?m fluorescence properties of Tm³⁺and Tm³⁺/Ho³⁺co-doped tellurite glasses have been investigated.It is found that when the concentration of Tm³⁺ion is 0.5mol%and the concentration of Ho³⁺ion is 1.5mol%,the fluorescence intensity of 2?m is the strongest.Under common 808 nm LD excitation,the maximum emission cross section of0.5Tm³⁺/1Ho³⁺co-doped sample near 2?m is 3.10×10^-21 cm² at 2048 nm.The extended overlap integral method is used to calculate the micro-parameters of the energy transfer from Tm³⁺to Ho³⁺,and the energy transfer coefficient is3.625×10^-40cm⁶/s.In the end of the paper,²?m fluorescence properties and the energy transfer between Tm³⁺/Er³⁺co-doped tellurite glasses under 808/980 nm LD excitation have been investigated.The mid-infrared fluorescence spectra show that when the doped Tm³⁺and Er³⁺concentration is 0.5mol%,the fluorescence intensity of 1.8 and 2.7?m is the strongest.Under the 980 nm LD excitation,the fluorescence intensity of 2.7?m is the strongest when the concentration of Er³⁺is 0.5mol%.The maximum emission cross section of0.5Tm³⁺/0.5Er³⁺co-doped sample can reach 4.68×10^-21 cm² at 1886 nm.When P is 0.4,the gain of Tm³⁺:³F₄?³H₆ transition at 1825-2100 nm starts to be positive.The maximum gain coefficient is 0.91 cm^-11 at 1887 nm.