Fabrication And Optical Fiber Fluorescence Temperature Sensing Property Of Er³⁺/Yb³⁺ Co-doped Fluorescent Materials

As a basic thermodynamic parameter,temperature is the expression of the kinetic energy of intermolecular thermal motion and an important indicator to characterize the progress of chemical reactions.It was used in industrial production,scientific research,medicinal chemistry,national defense construction and other fields.Therefore,improving the accuracy and precision of temperature measurement has great practical significance for the expansion of community.With the development of science and technology,fluorescent optical fiber temperature sensors have gradually attracted the attention of researchers due to their non-contact,high sensitivity,and anti-electromagnetic characteristics,and have become an important research object.The optical fiber temperature sensor based on fluorescence intensity ratio technology（FIR）uses the fluorescence intensity area ratio between the thermal coupling energy levels of rare earth ions to establish a corresponding relationship with temperature.System errors caused by power fluctuations can be reduced,and the temperature measurement resolution can be improved.In order to improve the temperature measurement efficiency,low-cost,high-sensitivity fluorescent materials are essential.Therefore,this paper takes the phosphor temperature-sensitive material as the research subject,designs and builds a set of optical fiber fluorescence temperature sensor based on the fluorescence intensity ratio technology,evaluates the temperature measurement capability of the system,and further explores its potential application prospects.Sm³⁺-doped and Er³⁺/Yb³⁺co-doped Li Gd（WO₄）₂（LGWO）phosphors were synthesized by traditional high-temperature solid-phase sintering method.The symmetry of the lattice occupied by Sm³⁺in Li Gd（WO₄）₂:Sm³⁺phosphors was analyzed.Bright green upconversion luminescence was detected in Li Gd（WO₄）₂:Er³⁺/Yb³⁺under 980nm laser excitation.By constructing an all-fiber temperaturesensor,thetemperaturesensingperformanceof LGWO:0.7%Er³⁺/5%Yb³⁺in the temperature range of 253～423K was studied,and the functional relationship between FIR and temperature was established.The highest absolute sensitivity reaches 0.0137K^-1at 423K,and the temperature measurement error is-0.7K⁰.4K,indicating that the optical fiber temperature sensor has good temperature reliability.Preliminary experimental results show that Er³⁺/Yb³⁺co-doped Li Gd（WO₄）₂phosphors have high up-conversion luminescence intensity and temperature sensitivity,and are expected to be used in fluorescence intensity ratio temperature sensors.Based on the fiber optic temperature sensor built in the previous section,a photothermal therapy platform based on fluorescence intensity ratio technology that can accurately feedback the temperature of deep tissue is optimized and demonstrated.The Li₂Zn₂（Mo O₄）₃:Er³⁺/Yb³⁺（LZMO）phosphors prepared by the high-temperature solid-phase method were excited by a laser with a wavelength of 980 nm,and a strong green up-conversion luminescence could be observed,and the thermal enhancement of the up-conversion luminescence reached 423K.The signal-to-noise ratio at high temperature is very,very favorable.And it shows excellent temperature sensing characteristics,the maximum absolute sensitivity reaches 89.9×10^-4at 423K,and the temperature measurement error is-0.4K～0.4K.Bright up-conversion luminescence and good temperature sensitivity can ensure its accuracy when measuring temperature.The integrated dual-function needle can realize temperature measurement and laser heating at the same time by using different laser powers,which is reflected in the egg white denaturation experiment and the pig liver laser thermal ablation experiment.The integrated platform can be further miniaturized by using customized needles and is expected to be applied to minimally invasive treatment of tumors,providing a new research direction for the development of fluorescent optical fiber temperature sensors in the medical field.