| 초록 |
Photonic crystals or photonic band gap materials (PBG) have been the subjects of intensive theoretical and experimental researches. Their periodic dielectric structures that are designed to control the propagation of electromagnetic (EM) waves by defining allowed and forbidden energy gaps in the photon dispersion spectrum. The absence of propagation EM modes inside the structures gives rise to distinct optical phenomena such as inhibition of spontaneous emission. Synthetic opals have been studied as pseudo photonic crystals to establish the growth techniques for the three-dimensional periodic structure. Previously, there have been many demonstrations that various materials can be infiltrated into interconnected nanosize voids of opals. Based on this fabrication technique, the concept of tunable photonic crystals are proposed, in which the photonic bandgap can be tuned as desired by controlling parameters such as the refractive index, periodicity, or space-filling factor. In this presentation, we proposed a novel photonic crystal in which the background index of colloidal opal crystal is gradually changed to specific direction of the crystal. This was achieved by infiltrating polymers using the interfacial-gel polymerization with relatively high refractive-index organic dopants. This method results in a novel infiltrated colloidal crystal that has graded refractive index distribution. Therefore, this device has gradually varying stop gap on the different position of the crystal. This could be a kind of tunable optical band-pass filter based on the positional variations. The optical properties and potentials for other optical applications were investigated. |
