Study On Wave-guide Theory Of Tapered Optic Fiber

As the development of photoelectron technology, Tapered Optic Fiber (TOF) is widely used in medicine, near-field optical microscope, soliton communication, moreover, it can be as imaging device by fusing to Fiber Optic Tapers (FOT). Currently, there are still some questions unsolved in the ray transmission and the energy distribution of TOF whether in the theory or in the experiment.In this paper, the problems of light-wave propagation in TOF are analyzed by employing the geometry theory and wave-guide theory, respectively. Monte Carlo method is mainly adopted to model and simulate light-wave transmission of TOF. The photon distribution and the intensity distribution after many photons transmitting TOF can be acquired. According to the result of the simulation experiment, the most photons transmitting TOF concentrate in the center of detector, the number of photons in the position decreased by increasing the distance between the position and the center of detector. Under the condition of certain taper ratio, the intensity reduced by increasing the length of TOF, the distribution of photons is invariable. When the refractive index of the external medium is in a certain area, the TOF in large taper ratio can transmit light without wastage. When the refractive index of the external medium falls in the range between the refractive index of the cladding and core, light output will be stable. When the refractive index of the external medium n_ex is close to the refractive index of the core n_co, the light output will approach zero. For the TOF in a certain taper ration, the absorbance will increase linearly with increasing the taper length. The absorbance of the cladding depends strongly on the refractive index of the external medium. The absorbance of the cladding will increase with increasing the refractive index of the external medium. However, if the refractive index of the external medium is close to the index of the cladding or the core, the absorbance will drop. The study results provide the important evidence for optimize design and application of TOF.