Leaky Radiation And Scattering On Microfiber Surface

As an important optical waveguide, microfiber has a lot of applications in information transmission and processing. Since eighties of last century, a special optical waveguide-micro optical waveguide gains many applications in optical coupler, optical sensor and supercontinuum generation. The micro/nano fiber is in a few or a wavelength scale, so it can provide a micrometer scale platform for fundamental research and technical application. Although micro fibers have many applications, the microfiber refractive index is lower than the environment medium refractive index in most applications up to now. The light can well be confined in the fiber. But when the medium refractive index is larger than the microfiber refractive index, the light can’t be confined in the waveguide well. The light will leak from the microfiber into the environment. This phenomenon gives a lot of disadvantage for microfiber applications. So this phenomenon should be avoided. In this thesis, we investigate the leaky radiation of microfiber, light scattering of microfiber and their possible applications.Firstly, we fabricate a new kind of optical fiber sensor based on microfiber leaky radiation. When the medium refractive index is larger than the refractive index of microfiber, the light will leak from the microfiber. Different radiation pattern will be observed in different refractive index medium. The microfiber leaky radiation simulation shows that the radiation angle agrees with theory. In experiment, clear radiation cone is observed. We have researched the dependence of radiation angle on medium refractive index.0.0013 refractive index change is detected in the experiment. The leaky radiations in different wavelengths show that this kind of sensor can be used in broadband and it has great sensitivity.Then, we researched the whispering gallery mode and scattering on microfiber surface. The experiment and simulation demonstrate that the scattering in microfiber will bring in obvious whispering gallery mode. The whispering gallery mode is dependent on the microfiber radius and medium refractive index.Last, we use microfiber as a measurement platform to excite the florescent sphere, and the florescence can be coupled with whispering gallery mode of the microfiber. We observed the florescent spectrum with whispering gallery mode. The simulation result demonstrates that the dipole can couple with microfiber whispering gallery mode...