Preparation, Characterization And Raman Scattering Properties Of Fluorotellurite Glass

Raman fiber lasers and Raman fiber amplifiers have the advantages of flexible output wavelengths and good beam quality,which meet the demand of a wide range of applications in optical communications,environmental monitoring,medical and health care,and defense and security.The advantages of tellurite glass are its high non-linear refractive index,wide infrared transmission window（0.4～6.5μm）,large Raman shift(660～790 cm^-1)and large Raman gain coefficient.The peak Raman gain coefficient is two orders of magnitude larger than that of silica glass.Recently,our group has explored fluorotellurite glass systems with a wide optical transmission window,high chemical and thermal stability,which have been proven to be a promising fiber laser material in the near and mid-infrared.However,the influence of the variation of the material components on the Raman scattering properties of this glass system has not been systematically investigated.Therefore,during the Master’s study,the authors focused on the preparation and characterization of the new fluorotellurite glass and the influence of different components on the Raman gain coefficient and Raman gain bandwidth,and achieved the following results:（1）Fluorotellurite glass samples were prepared by the melt-quenching method and subsequently tested by Raman scattering spectroscopy for different components of fluorotellurite glass.The peak Raman gain coefficient of 70Te O₂-20Ba F₂-10Y₂O₃ glass sample was calculated to be 2.48×10^-12 m/W,which is about 26.7 times of the peak Raman gain coefficient of silica glass material,and the Raman gain bandwidth was 4.65THz,using a 633 nm laser as the pumping source.（2）The modulation of the Raman gain spectrum shape and Raman gain coefficient was achieved by changing the components of the fluorotellurite glass sample.The largest Raman shift in the fluorotellurite glass system is located at～785 cm^-1,which is mainly attributed to the vibrations of the non-bridging oxygen bonds in the[Te O₃₊₁]and[Te O₃]units（Te-O^-and Te=O bonds）.In particular,the addition of Ba F₂ causes a gradual stretching or breaking of the Te-O bonds within the fluorotellurate glass atmosphere,a gradual conversion of the stretched Te-O bonds in the[Te O₃₊₁]group to Te-O^-and Te=O in the[Te O₃]units,that means increased content of non-bridging oxygen bonds,an increase in the Raman gain coefficient from 2.21×10^-12 m/W to2.82×10^-12 m/W,and the Raman gain bandwidth decreases from 5.91 THz to 2.55 THz.The addition of Y₂O₃ leads to an increase in[Te O₄]units within the fluorotellurite glass atmosphere,followed by stretching,lengthening and breaking of the Te-O bonds in the[Te O₄]units to form[Te O₃₊₁]units and[Te O₃]units,that means promoting the conversion of[Te O₄]units to[Te O₃₊₁]units and[Te O₃]units conversion,the content of non-bridging oxygen bonds increases,its Raman gain coefficient increases from1.76×10^-12 m/W to 2.48×10^-12 m/W,and the Raman gain bandwidth decreases from 6.21THz to 4.65 THz.