Spectroscopic Properties Of Ions-Activated Broadband-Emitting Germanate Glasses

Luminescence materials have been widely used in optical communication,optical information processing,laser sources,lighting sources and so on.In the field of transportation,the application of luminescence materials is necessary for the equipment such as tunnel lighting,beacon lighthouses,airport signs and indicators.In recent years,with the rapid development of science and technology,higher requirements have been put forward for the performance of devices based on luminescent materials in the field of transportation.To achieve higher quality lighting for transport vehicles,white light diodes（w-LED）with higher color rendering performance is being expected.However,the spectral range of luminescence materials used in commercial w-LED is relatively narrow at present,resulting in a low color rendering index of white light.Meanwhile,the spectral broadening and supplementation achieved by the combination of different luminescence materials inevitably leads to a decrease in the luminescence efficiency of w-LED.Using the single-component luminescence materials to achieve ultra-broadband emission,can not only effectively improve the color rendering index,but also avoid the decrease in luminescence efficiency.In addition,the demand for high-speed information transmission and tunable laser source is also increasing with the rapid development of the shipping industry.Consequently,the research on ions-activated broadband-emitting glass materials is of great significance for high-quality white light illumination and tunable solid-state laser.In summary,the research on new ions-activated broadband-emitting glass materials is carried out in response to the current problem of spectral component loss of polycrystalline phosphor conversion materials in w-LED and the urgent demand for new laser media in broadband tunable solid-state lasers.Based on this,a series of ions-activated broadband-emitting germanate glass materials have been designed and fabricated in this work.And,the luminescence and chromaticity properties,optical gain characteristics,and temperature sensing properties of the prepared ions-activated broadband-emitting germanate glasses have been deeply studied,and their potential applications in w-LED and tunable solid-state lasers have been explored.The main achievements of the study are as follows:（1）A series of germanate glasses with composed of 55K₂O-12Na₂O-3Zn O-5Mg O-17Al₂O₃-58Ge O₂-x Cu（NO₃）₂-y Tm₂O₃ were designed and synthesized.With the addition of graphite powder,Cu²⁺in germanate glass was successfully reduced to Cu⁺.Based on the characterization of the luminescence spectra,it was found that the Cu⁺doped germanate glass shows broadband luminescence emission covering almost the entire visible region.However,the relatively lack of blue spectral component ratios in the emission spectrum leads to poor colorimetric performance.Therefore,it was proposed to introduce Tm³⁺with blue emission into the glass system.With the introduction of Tm³⁺,Cu⁺/Tm³⁺co-doped germanate glass realized a series of full-spectrum white light emission,and the blue spectral component was effectively supplemented.Furthermore,the color coordinates,color temperature and color rendering index of full-spectrum white light can be effectively adjusted by the change of excitation wavelength and Tm³⁺codoping concentration.Through the measurement of temperature-dependent emission spectra,it was found that Cu⁺/Tm³⁺co-doped germanate glass has excellent thermochromic properties,and the emission of Cu⁺and Tm³⁺follows different temperature quenching laws.Based on this,a temperature sensing technology based on fluorescence intensity ratio（FIR）of dual center emission was proposed,and the temperature sensing characteristics were analyzed.（2）The broadband optical gain of Cu⁺/Tm³⁺single-doped and co-doped germanate glass was studied by amplified spontaneous emission（ASE）technique.It was found that the optical gain coefficient of Tm³⁺single-doped glass is much greater than that of Cu⁺single-doped glass.Meanwhile,the optical gain coefficients at Tm³⁺and Cu⁺emissions in Cu⁺/Tm³⁺co-doped germanate glass are greater than those of Tm³⁺and Cu⁺single-doped germanate glasses at the same wavelength.In addition,the optical gain coefficients of Cu⁺/Tm³⁺co-doped germanate glasses are of the same order of magnitude,and are maintained in a stable range at different wavelengths,which means that broadband gain has been flatted.All results confirmed that Cu⁺/Tm³⁺co-doped germanate glasses have potential applications in broadband tunable solid-state lasers.（3）Ag aggregate/Sm³⁺doped germanate glasses were prepared by high temperature melting method.Under different excitation wavelengths,the tunable luminescence emission of glass containing Ag-aggregate was observed,which confirmed the existence of different Ag-aggregate luminescence centers.With the codoping of Sm³⁺,a series of tunable full-spectrum white light with color coordinates ranging from（0.26,0.25）to（0.30,0.32）was achieved in the Ag aggregate/Sm³⁺co-doped germanate glass by changing the excitation wavelengths,and the color rendering index is up to 97.6.In the test of temperature-dependent emission spectra,the calculation of colorimetric parameters shows that the luminescence color coordinate of Ag aggregate/Sm³⁺co-doped germanate glass always lie in the white light region when the sample temperature increases from 301-693 K.In addition,a temperature sensing model was established based on the FIR between Ag aggregates and Sm³⁺.The spectroscopic,colorimetric,and thermal results suggest that Ag aggregate/Sm³⁺co-doped germanate glasses have broad application prospects in carrier lighting as w-LED materials.（4）A series of Ag aggregate/Mn²⁺doped germanate glasses was synthesized by high temperature melting method,and their spectroscopic and colorimetric properties and optical gain characteristics were investigated,respectively.It was found that Ag aggregates/Mn²⁺co-doped germanate glasses can generate ultra-broadband luminescence emissions that cover the entire visible region.Moreover,the interaction between Ag aggregates and Mn²⁺was studied through spectroscopic and luminescence dynamics measurements,confirming the existence of energy transfer from Ag aggregates to Mn²⁺.And,the colorimetric characteristics of luminescence emission from Ag aggregates/Mn²⁺co-doped germanate glasses were analyzed.Besides,the optical gain characteristics of Ag aggregate/Mn²⁺co-doped germanate glass were characterized by ASE technology.It was found that Ag aggregate/Mn²⁺co-doped germanate glass has high optical gain coefficients in the full visible range.The result indicates that Ag aggregate/Mn²⁺co-doped germanate glass material is a new type of broadband tunable visible laser working medium.（5）A series of Sn²⁺/Mn²⁺single-doped and co-doped germanate glasses were synthesized by high temperature melting method.A broadband luminescence emission with half-peak width（FWHM）of 142 nm was observed in Sn²⁺doped germanate glasses.By using the Van Uitert model,the influence of Sn²⁺concentration on luminescence properties was studied,and the optimal doping concentration of Sn O₂ was determined to be 1.0 mol%.When Mn²⁺was co-doped into Sn²⁺doped germanate glass,Sn²⁺/Mn²⁺co-doped germanate glasses realized ultra-broadband white light emission covering the entire visible light region.In addition,the temperature quenching of the Sn²⁺/Mn²⁺co-doped glass sample was analyzed by Arrhenius formula.Moreover,a prototype w-LED device was fabricated using Sn²⁺/Mn²⁺co-doped germanate glass and a 310 nm chip,and the spectral testing and colorimetric parameter calculation of the fabricated device were carried out.It was found that Sn²⁺/Mn²⁺co-doped germanate glass is an excellent candidate material for achieving light-conversion w-LED with high chromaticity performance.