Estimation of beads distribution inside an electroactive photonic crystal system

Abstract

Electroactive soft photonic devi ces such a s an opal photonic crystal in gel shown in Fig. 1 (a) reflect light. The o pal photonic crystal consist s of beads array in a continuous medium and the reflection characteristics vary according to the inter p article distance of the beads . When an external voltage is applied to the V e r y H igh B ond ( tape layer , the area of the VHB expands while the thickness s hrinks in accordance with phenomena related to Maxwell stress As a result the inter particle dista nce can be adjust ed by an external voltage and if the more precise ly the beads structure is controlled, the more quan ti tative ly accurate color control and consequently improve d color characteristics can be expected . it has been hard to know how th ose beads are distributed exactly . In this paper, the authors estimate the structural a rrangement of the beads through Finite Difference T ime domain ( method and experimentally evaluate properties of the relfected light Photonic crystal samples are m ade by a gelation process that alters the arrangement of the beads. By controlling the gelation conditions continuous color shift of reflected light is observed. The beads distribution was known as FCC (111), however the arrangement after gelation may be different . Hence , we simulate reflection spectrum of the beads alignments in Fig. 1 (b) and measure reflected light from samples under various voltage applic ation According to the previous studies , isotropic 3 ]], vertical (layer to 4 or core sh el l 5 alignment may be assumed a s an initial state The i nitial condition s of each types are designed to reflect red light , and the reflect ed light spectrum s for various thickness are calculated by using FDTD method In FCC structure, where the beads stack layer by layer, t he distance between layers affects the wavelength of a reflection peak an d the distance between beads in a layer is related to the inten sity of the reflection Considering t hese structure dependent characteristic s , we estimate beads arran gement T he FCC structure was used as a template for the series of simulations. For various thickness conditions of the photonic crystal layer, the peak wavelength and intensity of reflected light a re computed. Through the compar i s on of the simulations and experimental measurements, authors estimate photonic crystal structure and the method will be applied for photonic crystal media to control color more accurately.