Research On The Condensing Characteristics Of High-intensity LED Light Source Based On Tapered Fiber

As the fourth-generation lighting source,LED has many advantages such as energy sav-ing,long service life,green environmental protection,and fast response speed,and is widely used in various fields.However,LEDs cannot be used alone as high-illuminance light sources due to its large divergence angle,heat dissipation problems and size limitations of optical modules also affect the development of high-illuminance light sources in the microscopic area.Tapered fiber is a special fiber with tapered processing,and its axial gradient structure makes it have good light-gathering properties.A method of obtaining high-illuminance LED light sources is proposed by combining LED light sources with tapered optical fibers.Using the Monte Carlo method to explore the condensing characteristics of LED light source based on tapered fiber.The main content of the thesis includes the following aspects:Firstly,the optical characteristics of LED light sources and the transmission character-istics of tapered optical fibers are introduced,and the Monte Carlo method and the basic idea of using this method to study the light-guiding properties of tapered fibers are intro-duced.These lays the theoretical foundation for the research of transmission characteristics of high-intensity LED light sources based on tapered fibers.Secondly,based on the concentrating properties of tapered optical fibers,a method to obtain high-intensity LED light sources in a microscopic environment is proposed.Through the adjustment and optimization of the structural parameters of the step-index tapered fiber and the tapered helical bent fiber,the best spot performance is obtained,including the light spot illumination and divergence angle at the output end of the fiber.The numerical simula-tion results show that the step-index tapered fiber can focus the LED divergent light on a tiny plane.When the fiber length is 75 mm,the cladding radius of the small end is 0.2 mm,and the cladding radius of the big end is 0.5 mm,the spot illumination reaches 0.9925 lm/mm~2,and the divergence angle is 62.76 degrees.For the tapered helical bent fiber,the optical loss in the cladding area will increase with the increase of the transmission distance,and the core part becomes the main area of light transmission,causing the spot energy to gradually decrease outward from the center of the core.Finally,to consider the influence of the cladding structure,the light-gathering effect of the tapered microstructured fiber and the tapered coreless fiber is further explored.There is a photonic band gap in the tapered microstructured fiber,and the phenomenon becomes more obvious as the fiber length increases,and the photonic band gap coincides with the cladding air hole region.When the fiber length reaches a certain threshold,the spot shape,energy and divergence angle tend to be consistent.Compared with other types of tapered fibers,the tapered coreless fiber has the most obvious light-concentrating effect,the spot size is the same as the output end of the fiber,and the spot energy is evenly distributed.When the length of the coreless fiber is 200 mm,the radii of the small end and the big end are 62.5μm and 125μm,respectively,the spot illumination can reach 1.98 lm/mm~2,and the divergence angle is 68 degrees.