Study On The Electirc Ifeld And Energy Distirbution Of Micro/nano Optical Fibers

In recent years, photonic devices are rapidly developing in the direction of micromation,and many micro/nano photonic devices with high integration, small size and excellentperformance have appeared. As an important part of micro/nano photonic devices, micro/nanooptical fibers have many excellent properties such as large evanescent field, strongconfinement, low bending loss, good flexibility and high mechanical strength. Therefore,more and more researchers have focused on the study of micro/nano optical fibers.Firstly, the electric field and energy distribution of the single straight micro/nano opticalfiber were studied. Core diameter and incident wavelength both have an influence on electricfield and energy distribution for the single straight micro/nano optical fiber. As themicro/nano optical fiber’s core diameter increasing, electric field norm and energy densitytime average of its core center will increase at first, then decrease, and the maximum ofelectric field norm and energy density time average are obtained when core diameter is closedto incident wavelength. The larger incident wavelength is, the smaller electric field norm andenergy density time average of micro/nano optical fiber are. When the core diameterincreases, the energy restrained in the core always increases when incident wavelength isconstant. And the smaller incident wavelength is, the more the energy restrains in the corewhen the optical fiber’s diameter is constant.Then, the electric field and energy distribution of the bent micro/nano optical fiber werestudied. The micro/nano optical fiber bending usually can be divided into same and differentdirection bending, both of which make electric field and energy distribution moves from thecenter. The more significant displacement can be observed for the smaller bending radius.Besides, the research about the influence of core diameter, core material, bending radius andincident light on the bending loss of micro/nano optical fiber was also carried out. The resultsindicated that the bending loss reduces gradually when the core diameter increases, moreover,bending loss increases more rapidly for the optical fiber with a smaller core diameter. Thebending loss tends to steady when the core diameter increases to a certain value, and a verysmall bending loss can be observed. Similarity, it can be concluded that the increase of coreindex and bending radius both reduce the bending loss. The influence of polarization state onthe bending loss is ignorable if the index difference between core and cladding or bendingradius is large. However, for the optical fiber with small index difference or bending radius,bending loss is related with polarization state of incident light, and it is larger for the incidentlight with longer wavelength. Meanwhile, for the optical fiber with different and samebending direction, the former has a larger bending loss than the latter. Finally, the U-typemicro/nano optical fiber sensor was designed to measure the refractive index, which is basedon the above mentioned bending loss research. It has a number of ways to measure therefractive index of external environment.Finally, the coupling characteristics of three parallel micro/nano optical fibers werestudied. The results showed that the coupling energy distribution are approximation as thetransmission distance changing when the distance between parallel micro/nano optical fibersor polarization state of incident light is changed. The distribution are periodical and coupling periods increase when the distances increase. The polarization state of incident light has aslight influence on coupling periods. And by utilizing the coupling characteristics amongthree parallel micro/nano optical fibers, a3x1micro/nano optical fiber coupler is designed.The length of this coupler is only a dozen micros and much smaller than the ordinary fibercoupler. And this coupler realizes that three beams are synthesized into one beam and itscoupling efficiency is greater than90%.