The Investigations On Bi-doped Glasses And Fibers With Broad Emission Covering S+C+L+U Band

Bi-activated laser glass and fiber have been evolving into a new generation of laser media,presenting great potential in the field of ultra-wideband optical amplifiers and tunable lasers.However,the near-infrared luminescence of traditional Bi glass and fiber can only cover a part of the communication window.And their emission is mostly located in the O-band(1260-1360 nm).It is tricky and difficult to further extend it to the important optical communication bands,including S(1460-1530 nm),C(1530-1565 nm),L(1565-1625 nm)and U(1625-1675 nm)bands.Broadening the Bi near-infrared(NIR)emission contributes to achieving optical amplification of the entire optical communication window by single element doping and single wavelength excitation.The implementation of such ultra-wideband optical amplifiers is likely to fundamentally break through the bottlenecks of modern communication system.In addition,Bidoped glass and optical fibers face problems such as low efficiency,inhomogenity,and severe thermal degradation.Achieving efficient,ultra-wide and stable Bi NIR emission will help to fundamentally solve the bottleneck of Bi-laser media,including gain and bandwidth,which will surely contribute to the realization of tunable lasers covering the entire near-infrared region.To deal these problems,a series of Bi-doped multi-component glasses were designed,fabricated and studied.The research results obtained and highlights are as follows:(a)We have fundamentally improved the luminescence efficiency of Bi-doped glass.We proposed a new strategy to enhance and stabilize Bi NIR emission at low Bi doping concentration by doping nitride and tailoring glass local structure.Bi NIR emission is enhanced by 1000 times by addition of nitride.In addition,the typical absorption of Bi is also enhanced.By this method,Bi-doped glasses with low Bi concentration presents highly efficient NIR emission with long decay lifetime,whose emission intensity is comparable to that of glass sample with optimum concentration The decay lifetime of Bi-doped glasses is twice of that from sample with optimum concentration.And,we have confirm the conclusions by adding nitride to other typical glass systems.This method,which optimizes the NIR emission properties of Bi-doped glass without significantly changing the structure of the glass network,solves the problem of luminous efficiency of low-concentration Bi doping and could contribute to the design and preparation of Bi-doped multi-component glasses with high gain.(b)We have highly broadened the NIR bandwidth of Bi-doped glasses.For the first time,we have achieved an ultra-wideband,tunable and long-life NIR emission through reduction and addition of nitride into glass composition.This NIR emission,with FWHM of 650 nm,covers 750-1900 nm region and presents high-efficiency and long-life of Bi NIR emission.It covers bio-imaging window and optical communication window(O-U band).In addition,we verified the universality of this strategy in silicate-germanate,boro-germanate and phosphate-germanate glasses.The significant enhancement and broadening of Bi NIR emission in Bi-doped glasses could contribute to the development and application of novel Bi-doped luminescent materials and devices with super-broad band NIR emission,which will lay the foundation for the realization of new Bi-doped multi-component optical fibers and fiber lasers.(c)We have solved the problem of thermal degradation and inhomogeneity of Bi-doped glasses.Via doping nitride and tailoring local glass structure.We have prepared a series of Bidoped multi-component glass without thermal degradation.The results indiate that the addition of nitride helps to increase the local rigidity of the glasses,making the glass structure more compact,which is conducive to the stable and efficient illumination of Bi NIR centers.The Bidoped multicomponent silicate glass presents no thermal degration when heated to 450 K.The Bi NIR emission in this new type of Bi-doped glass is still able to restore the original luminescence intensity under multiple cycles of heating.And the Bi-doped multi-component glass presents good uniformity.These results will pave the way for the performance optimization of Bi-doped multi-component glass and fiber.(d)We have revealed the relationship between the novel Bi near-infrared luminescence behavior and the glass structure.We realized Bi-activated ultra-wideband NIR emission in Bidoped borogermanate and fluorogermanate glass by doping nitride,and explored the dependence of Bi ultra-wideband NIR luminescence on local glass structure in detail.The experimental results show that the luminescence properties of the novel Bi NIR centers are not only affected by aluminum coordination,but also by the phonon energy of the glass.And different Bi NIR centers present diverse dependence on the glass structure.These results could help identify the origin of Bi NIR luminescence and deepen our understanding of Bi NIR luminescence behavior,which provides a reference for the regulation of Bi NIR luminescence.(e)For the first time,we have successfully prepared a new Bi-doped multi-component fiber with superbroad band NIR emission.We found that Bi-doped multicomponent germinate fibers also exhibit a similar ultra-wideband NIR luminescence with that of core glass.The NIR emission in new Bi fiber also cover the entire NIR region including the important optical communication window(O-U band).The results obtained indicate that the new Bi NIR center in glass can survive the secondary heating process of fiber drawing.These results contribute to the development of Bi-doped multi-component glass fiber with high gain and high bandwidth(>650 nm)for ultrabroad band amplifier and tunable lasers.