Research On Bismuth Doped Glasses And Their Applications In Ultrabroadband Near Infrared Led Light Source

In recent years,due to the wide application of near infrared（NIR）spectroscopy technology in varieties of fields such as biomedicine,food industry,smart wearable devices and so forth,the development of novel broadband NIR light source based on light conversion technology has attracted extensive attentions,and become one of the popular research directions.Lots of progress has been made,however,several important problems remain unsolved.Firstly,most reported NIR phosphors only show a NIR emission in the region of 650-1000 nm with limited bandwidth.Secondly,numerous NIR phosphors suffer from serious thermal quenching and even change the emission profile upon heating.Thirdly,the packing steps of NIR phosphor-converted LED are complicated,and the organic resin packing materials with low thermal conductivity can easily cause heat accumulation,resulting unstable NIR emission.In order to solve these problems,in this work,we innovatively propose Bi-doped glasses with excellent spectral characteristics as the light convertor.By modular structure,a blue LED driven ultrabroadband NIR light source with a FWHM more than 500 nm is designed and realized.Using the ultrabroadband NIR light source,we developed a miniaturized and portable NIR absorption spectrum analysis system,which proves the application potential and prospects of the ultrabroadband NIR light source.The main research contents are as follows:1.By studying the common spectral characteristics of a series of Bi doped glasses（silicate,germanate,phosphate and borate matrix）,it is proved that Bi doped glasses are feasible and universal to be used as the light convertor.In order to further broaden the NIR luminescence of the Bi-doped glasses,we adopt two research ideas:Firstly,by codoping strategy,the Bi/Er codoped germanate glass was prepared.The energy transfer between Bi NIR emission center and Er³⁺was studied in detail.The quenching behavior of Bi NIR emission center and Er³⁺at different temperatures（10-393 K）was explored.It was found that the energy transfer from Bi NIR emission center to Er³⁺is temperature dependent,and the increase of temperature can promote the energy transfer from Bi NIR emission center to Er³⁺.The dependence of NIR emission intensity on excitation and emission wavelength in Bi/Er codoped glass is studied,which provides an optimizing scheme for the realizing ultrabroadband NIR emission.Secondly,by introducing Si C strategy,the Bi-doped germanate glass was prepared,which shows an ultrabroadband NIR emission with a FWHM more than 500 nm,covering the spectral range of800-1700 nm.The Bi-doped germanate glass shows good thermal stability,and the integral intensity of the NIR emission only decreases by 15.8%when the temperature is increased from303 to 423 K.The hardness,transmittance spectrum and integral intensity of the Bi-doped germanate glass only show slight changes after different duration time（0-12 days）in an environment with relative humidity of 90%and temperature of 393 K,indicating that it has good reliability in extreme environments.2.Using a Bi-doped germanate glass as the light convertor,we successfully construct a blue LED driven NIR light source in a modular way,which can provide ultrabroadband NIR emission covering the spectral range of 800-1700 nm with a FWHM of 530 nm.The spectral stability of the broadband light source has been studied,when the input current is 240 m A and the input power is 0.72 W,after continuous operation,the ultrabroadband light source can still sustain 95%of the initial intensity,showing excellent spectral stability.3.By using the ultrabroadband NIR light source,a homemade portable NIR absorption spectrum analysis system is constructed.We successfully obtained the transmittance spectra of water,ethanol and oleic acid.After comparing with the standard data,we find that the test results have good accuracy and reliability,which proves a broad application prospect of the ultrabroadband NIR light source in modern industry.