Study On The Optical Eigenmodes In Nanostructures And Their Applications In Optoelectronic Devices

With the development of micro/nano fabrication technologies, the size ofoptoelectronic devices has been scaled down to the order of nanometers. These nanooptoelectronic devices have attracted much attention due to their intrinsic merits ofhigh-speed and low power consumption. However, the scaling down of the devicesize may weaken the light-matter interaction and then affect the device performance,such as the detecting sensitivity in sensors or the absorption efficiency in solar cells.We need to study how to manipulate the light propagation and distribution in the nanooptoelectronic devices. Nanostructures can support various optical eigenmodes, and atthe resonance of these optical eigenmodes, light-matter interactions can be enhanceddramatically, which will help to improve the device performance. In this thesis, wewill first study the characteristics and manipulations of the optical eigenmodessupported in the nanostructures, and then apply these modes to nano optoelectronicdevices for improving the device performance. The research results include thefollowing aspects:(1) Study on the dispersion of optical eigenmodes in nanostructures. Thedispersion in a metal-dielectric multi-layered nanostructure has been studied, with thefindings of the super-long range surface plasmons with ultra-small mode losses.Based on the mode, a sensor for detecting the refractive index of fluids has beendesigned. The dispersion in metal/DBR nanostructure has been studied, with thefindings of evanescent optical Tamm states. A design concept of eliminating theangular dispersion in microcavity has been proposed by employing anisotropicepsilon-near-zero metamaterials as reflectors. By exploiting optimal constitutiveparameters of the metamaterials, a microcavity without angular dispersion can beestablished.(2) Study on the light trapping schemes for thin-film solar cells. A concept ofintroducing optical Tamm states in thin-film solar cells for increasing the light absorption in active layers has been proposed. The conventional microcavityresonance based light trapping scheme has also been studied for comparison. Forplanar devices, both schemes based solar cells exhibit comparable absorptionperformance. While for corrugated devices, the proposed optical Tamm states basedscheme exhibits a higher performance. Thin-film solar cells with ultra-thinhighly-absorbing dielectric based anti-reflection resonances have also been proposed.(3) Study on the light outcoupling schemes for organic light-emitting devices.The grating amplitude effect in organic light-emitting devices has been studied, withthe findings of the optimal grating amplitude of~50-70nm. A strong couplinginduced hybrid modes based light outcoupling strategy has been proposed for thewhite top-emitting organic light-emitting devices, towards maintained high quality ofwhite color, improved viewing characteristics and electroluminescence efficiency.(4) Study on the optical eigenmodes from the viewpoint of multipoles. Opticalforce acting on toroidal objects has been studied with the help of multipoleexpansions. By introducing conceptions such as raw multipoles, irreduciblemultipoles and renormalized multipoles, the origin of optical forces has beeninterpreted from two viewpoints based on induced charge/current distributions andvector spherical functions, respectively.