Fabrication And Optical Signal Amplification Of Er³⁺/Yb³⁺ Ions Codoped Germanium Tellurite Glass Fiber

With the expansion of optical fiber communication capability and the rapid development of computer network functionalization,traditional erbium-doped fiber amplifier with the optical amplifier bandwidth of only 35 nm cannot satisfy the development of optical communication in the future.Therefore,seeking new type of optical fiber amplifier materials to achieve broadband gain-flatten fiber amplifiers and expand the operating wavelength to the area beyond C-band,has become the most urgent task.Based on this consideration,Er3+/Yb3+codoped heavy metal germanium tellurite glass fiber amplifier were designed and fabricated,and the optical and spectral properties of Er3+ were studied,which lays the foundation for Pr3+,Tm3+ and Ho3+-doped multicomponent heavy metal germanium tellurite glasses for special-band signal amplifier.The followings are results this work achieved:1.Er3+/Yb3+ co-doped heavy metal germanium tellurite glasses have been designed and fabricated.Based on optical absorption,Judd-Ofelt parameters ?2,?5 and ?6 have been derived to be 6.777×10-20,1.536×10-20 and 1.167×10-20cm2,respectively.Then the radiative transition probabilities,radiative lifetimes and fluorescence branch ratios of Er3+ in NZPGT glasses were calculated.The efficient infrared emission in Er3+/Yb3+ co-doped heavy metal germanium tellurite glass system has been recorded under the pumping of a 982nm diode laser and Yb3+ is considered to be a preferable sensitizer for catching remarkable pumping energy and transferring considerable energy to Er3+.The maximum absorption and calculated emission cross sections are 7.77×10-21cm2 and 7.53×10-21cm2 at 1.53?m,respectively.Low maximum phonon energy and high emission cross sections indicate that Er3+/Yb3+ co-doped heavy metal germanium tellurite glasses will be promising infrared laser materials.2.Optical fiber preform is composed of a core and a cladding,the refractive index of rare earth doped fiber core is greater than that of the cladding,which is in the required range of the relative refractive index.The temperature difference values of crystallization temperatures and transition temperatures in Er3+/Yb3+ co-doped heavy metal germanium tellurite core and cladding glasses are large than 100?,indicating that the heavy metal germanium tellurite glasses exhibit good stability against crystallization,and it can be considered a good candidate for fiber drawing.In addition,the transition temperatures of the core and the cladding glasses are similar,indicating that they can be melted under the identical condition of temperature in the fiber-drawing process.3.Er3+/Yb3+ co-doped heavy metal germanium tellurite glass fibers with good flexibility and excellent thermal stability were fabricated by rod-in-tube technique and their optical performance were characterized.The relative refractive index of the core and cladding glasses,the near-field pattern diameter and the numberical aperture were calculated to be 0.84%,5.56?m and 0.24.The optical gain and relative gain coefficient of a 5.3cm long fiber amplifier were measured to be 33.16dB and 6.26dB/cm at 1536nm wavelength,respectively,and after compensating both the propagation loss and the absorption loss,a positive maximum internal gain of 12.59dB at 1.536?m was obtained.The gain coefficient of the Er3+/Yb3+co-doped heavy metal germanium tellurite glass fiber is obtained to be 2.38dB/cm,which is higher than those of cesium-silicate and tellurite glass fibers.The promising signal amplification capacity of the Er3+/Yb3+ co-doped heavy metal germanium tellurite glass fiber demonstrates that NZPGT glass fibers have a promising potential for the development of rare-earth doped fiber amplifiers.The present research indicates that rare-earth doped heavy metal germanium tellurite glass fibers with excellent thermal stability is an attractive material in fabricating particular wavelength band glass fiber amplifier.Based on the successful preparation of Er3+/Yb3+co-doped heavy metal germanium tellurite glass fiber and its excellent properties of signal amplification,we believe that the Pr3+,Tm3+ and Ho3+ doped NZPGT glass fibers with medium-low phonon energy and UV sensitivity are expected to be used as potential and attractive candidates for developing efficient O-,S-,and U-band amplifiers and eye-safe medical lasers.