Ray Tracing Simulation Study Of Rare Earth Doped Upconversion Micro-nano Optical Waveguide

Micro-nano optical waveguide is a kind of dielectric waveguide which can limit and guide light propagation in the structure at micro-nano scale.With the rapid development of micro nano fabrication technology,in recent years,active optical waveguide devices based on silicon semiconductors,polymers and self-assembled organic molecules have been widely used in the field of integrated optical chips.The optical waveguide composed of rare earth upconversion luminescent materials can realize the waveguide transmission function of fluorescence under the excitation of near infrared light,and has the advantages of deep biological penetration and low toxicity.Therefore,it is expected to play an important role in the application of integrated optical chips in optical communication and biological imaging.Because the rare earth particles have many different morphologies and sizes,the corresponding transport modes are different.Due to the different morphology and size of rare earth particles,the corresponding transport modes are different.Therefore,in order to explore the detailed process of coupling and transmission of excited light and fluorescence in rare earth micron optical waveguides with different shapes and sizes,appropriate optical simulation methods and models need to be adopted.At present,there are two main methods for optical model simulation:one is the finite element method based on electromagnetic wave theory,which is characterized by accurate simulation results and not limited by diffraction limit,but with a large amount of calculation.Therefore,it is generally used to analyze the transmission modes of siliconbased optical waveguides and other devices whose size is less than the diffraction limit.The other is the ray tracing simulation method based on the principle of geometrical optics,which is characterized by fast calculation and more accurate simulation results on the optical model which is larger than the diffraction limit.For devices such as silicon-based optical waveguides whose size is less than the diffraction limit,the finite element method based on electromagnetic wave theory is generally used to analyze the transmission mode.However,at present,there are few literatures about the simulation of rare earth optical waveguides.Therefore,based on the non-sequential ray tracing simulation method,this thesis simulates the optical waveguides and emission phenomena of two kinds of rare earth doped upconversion luminescent micron particles with different morphologies and sizes larger than the diffraction limit.The main research contents are as follows:(1)The different transmission characteristics of excited light and fluorescence of oblique-cut microtubes at the end of NaYF₄:Yb³⁺/Er³⁺under different excitation conditions are simulated.Through the simulation,it is found that when the laser excites the middle part of the micron tube,only the fluorescence can be coupled into the waveguide transmission in the micron tube;under the condition of the excitation end,it can realize the waveguide transmission function of coupling excitation light and fluorescence at the same time;in addition,changing the angle between the end of the micron tube and the laser can adjust the coupling ability of the micron tube to the laser.Finally,compared with the actual experimental results,it is found that the simulation results are basically consistent with the actual phenomena.(2)On the basis of the above methods,the luminescence image of NaYF₄:Yb³⁺/Er³⁺crown micron waveguide and the spatial angular emission of fluorescence are simulated.By changing the size and position of the fluorescent light source model,the influence of the fluorescent light source model on the luminescence image of the particles is analyzed,and a more practical fluorescent light source model is selected to simulate the real fluorescent waveguide angular emission luminescence image in the experiment.Finally,the changing trend of the fluorescence spatial emission angle of the crown micron waveguide is studied by changing the position of the fluorescence light source,and it is found that the simulation results are the same as the experimental results.