Propagation Properties Of Optical Nanowires With Thin Dielectric Coatings

Subwavelength-diameter optical devices are widely applied in opticalcommunication, optical fiber sensing, optical power delivery system and so on.Nanowire is the main component of the subwavelength-diameter optical device. It isthe hot point of the photonics research realm recently. Micro/nano fiber is the typicalkind of nanowire. It attracts more and more attention because of its low loss, andsimple preparation.Strong evanescent field is its outstanding advantage. This wire exhibits greatpotential for a variety of applications, such as optical fiber sensing, optical coupling.Previous work has shown that micro/nano fiber provides the opportunity for obtainingwaveguide dispersion one or more magnitudes larger than those of conventionalwaveguides. Based on reasonable design, the micro/nano fiber of high dispersionshows great potential application in optical communication and so on. Minimumregulation and optimization of its parameters may lead to the tuning for dispersionand modal field.At first, the thesis presents the background in studying the micro/nano fiber andthe structure of the thesis. Next, it summarizes the basic theories and methods of theresearch. Finally, the thesis focuses on the electromagnetic wave propagationcharacteristics of both isotropic and uniaxial thin index dielectric coated micro/nanofiber, the modal field and waveguide dispersion have been discussed. The mainachievements of this work consist of following aspects:(1)Based on exact solutions of Maxwell’s equations of a3-layer structuredcylindrical waveguide, the electromagnetic wave propagation characteristics of theisotropic fiber with thin index dielectric layer have been studied. The influences ofthickness and refractive index on the modal characteristics and energy flow densityhave been discussed in detail. Numerical simulations show that the modalcharacteristics vary little in the fiber core and thin dielectric regions, while vary muchin the fiber outer cladding. The research of propagation properties of opticalnanowires with thin dielectric coatings may provide useful guidelines for bothpreparation and taloring the nanowires.(2)Using exact solutions of Maxwell’s equations, the modal characteristics andwaveguide dispersion of the uniaxial thin index dielectric coated micro/nano fiberhave been studied, too. The thin dielectric layer has an obvious effect on the modalcharacteristics and the waveguide dispersion. Investigation of energy flow along the propagation direction shows that the higher the film thickness, the lower the energyflow density in the film. The refractive index of the core plays an important role forthe waveguide dispersion compared with the thickness of the dielectric layer. It isshown that the thin dielectric layer imposes redshift effect on the waveguidedispersion. Compared with the isotropic thin index dielectric coated micro/nano fiber,it shows different characteristics in dispersion.