Strong Light Confinement in Novel Compact Pseudo-Random Structures Designed via Evolutionary Algorithms

Abstract: High optical confinement of 1.55,um light is shown in a 5 Am sized high-index-contrast pseudo-random distribution of dielectric rods. This structure, designed using Evolutionary Algo-rithms, utilizes Anderson Localization to achieve confinement. © 2005 Optical Society of America OCIS codes: (230.5750) Resonators; (030.0030)Coherence and statistical optics In random media, when the separation distance between high-index contrast scattering sites is on the order of the wavelength, interference from multiple scattering events can result in a wave propagation phase transition [1]. Media satisfying this condition is referred to as strongly scattering. Depending on the size and arrangement of the strongly scattering media, light can cease classical diffusive propagation and form localized stationary eigenstates (Anderson Localization) [2]. For waves confined to one or two dimensions localization always occurs in the limit that the size of the disordered media reaches infinity [2]. In contrast, for finite size media, light leakage results in finite lifetimes of the eigenstates and consequently a broadening of eigenstate energy levels. According to the Thouless criterion, a localized eigenstate persists as long as the spacing between the energy levels of different eigenstates is larger than the spectral width of the state [3]. Mathematically this can be represented as a Thouless number ('yT) less than 1 where W = Y5T- '5w, Sw is the full width at half maximum (FWHM) spectral width of the eigenstate and Aw is th