Manipulating Nematic Liquid Crystals-based Magnetophotonic Crystals

Abstract

Magnetic materials have attracted considerable attention for their applications in high density magneto-optical storage devices, which is not only appealing scientifically, but also makes the magnetic materials promising for a wide range of applications [1-11]. Due to their unique optical properties, magnetic materials have been introduced into the photonic crystals, forming magnetophotonic crystals (MPCs), i.e., the photonic crystals with at least one magnetic material component [2,3]. Now the optical properties can be mediated and controlled by the external electric or magnetic field due to the existence of magnetic materials. The special importance of MPCs can be ascribed to the existence of magneto-optical effects, for example, Kerr effect and Faraday rotation [12-28]. They were discovered by Kerr and Faraday, respectively, and are now widely used in integrated optics and magneto-optical devices for magnetic domain imaging, mapping of hysteresis loops and high density recording [6]. Magnetic materials with large magneto-optical responses are always the attractive ones used in magnetophotonic crystals. In contrast to the corresponding three-dimensional magnetic structures, magnetic materials exhibit a larger magneto-optical effects due to the light's confinement in the MPCs, offering a genuine chance to put their optical responses into applications. The optimized MPCs have been shown to behave like mixed systems, with a coexistence of high transmittance and large magneto-optical effects [12-28]. All possible configurations are proposed to achieve strong magneto-opitcal effects, including the ordinary cavity-based, multilayered periodic and aperiodic structures. Furthermore, the diffracted magneto-optical enhancement is also demonstrated in the grating structures theoretically and experimentally, which greatly reduces the thickness of the device contrary to multilayered structures and miniaturizes magneto-optical devices in integrated optics [29,30]. The ability to tune the otpical properties by an external stimulus is a key issue of modern optoelectronics. Although most attention has so far been focused on the magneto-optical properties of the given structures, tunable magneto-optical devices have important applications and will be respected in optical switches and displays. There are few reports concerning with the tunable magnetophotonic crystals [31-33]. For example, it is possible to manipulate the magnetic order of magnetic conducting spheres using the magnetic field, thus forming the tunable magnetophotonic crystals [31]. Semiconductor quantum well has