One-dimensional photonic crystals containing memory-

enabling liquid-crystal defect layers

Prof. Wei Lee ( б)

Abstract

    Incorporating liquid crystal (LC) as a defect layer in a photonic crystal (PC) leads to the electrically tunable optical spectrum in defect modes within the photonic band gap. Such a superior feature makes the hybrid structure potential for designing various types of optical devices. Recently, we have demonstrated several types of photonic structures based on one-dimensional (1-D) PC containing memory-enabling LC (MELC) as a defect layer. The optical state remains unchanged after removal of applied voltage in the memory state. The defect modes of a PC/MELC cell can be switched to not only the dynamic or voltage-sustained states but the memory or optically stable states as well. Owing to the fact that the spectral properties of defect modes in a memory state persist without applied voltage, the device will support the green society of tomorrow. The wavelength tunability, amplitude tunability and optical multistability of the defect modes permit the 1-D PC/MELC cell to be alluring for photonic device applications such as low-power-consumption multichannel filters, light shutters or electrically controllable intensity modulators without any polarizers.

    In this colloquium, I shall report on our recent development of various one-dimensional PC/LC hybrid cells for photonic applications. Special attention will be paid to the optical and spectral properties of multilayer PC structures containing a bistable chiral-tilted homeotropic nematic (BHN) layer, a bistable chiral-splay nematic (BCSN), a bistable dual- frequency cholesteric LC (DF-CLC) layer, a tristable polymer-stabilized cholesteric texture (PSCT), and a tristable smectic-A liquid crystal as a defect layer

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