A narrowband guided-mode resonance filter (GMRF) incorporating polymer-dispersed liquid crystal (PDLC) is designed. Simulating the characteristics of the filter with rigorous coupled-wave analysis, we find that the resonance wavelength of the new kind of GMRF can be tuned from 672.4 to $698.4\mathrm{nm}$ by varying the refractive index of the PDLC layer with the applied voltage. Furthermore, the resonance wavelengths vary in a linear fashion with respect to the refractive index of the PDLC layer. Therefore, the desired resonance wavelength can be conveniently selected and tuned in a tuning range of $26\mathrm{nm}$ by using the applied voltage.

A theoretical study was conducted with the aim of improving the detection accuracy of graphene-based surface plasmon resonance (SPR) biosensors. We studied the effect of applying a bias voltage to the sensor surface on its detection accuracy. The optimum thicknesses of silver and gold layers in the biosensor of 47 nm and 3 nm, respectively, were determined. Graphene layers deposited on these thin silver and gold films formed a sensor surface system, on which the surface plasmons were excited. The real and imaginary parts of the refractive index of graphene were controlled by the bias voltage. When the chemical potential was increased from 36 meV to 8 eV, the detection accuracy of the sensor was correspondingly increased by 213%.

Advanced, predictive numerical tools for liquid crystalline polymers (LCPs) are well established. These tools yield descriptive features (steady and unsteady behavior, gradient morphology) of LCPs in the bulk and in confined geometries; some are applicable to LCP hydrodynamics. Our goal here is to expand the hydrodynamic toolkit (a predictive theory, algorithms, and simulations) to two-phase fluids consisting of an immiscible LCP phase (initialized as droplets) dispersed in a viscous or polymeric phase. To do so, we bridge the modeling and simulation gap between molecular dynamics and Monte Carlo discrete lattice models for polymer-dispersed liquid crystal (LC) droplets and continuum scale, diffuse interface methods for LC droplets in viscous fluids. We give a brief overview of molecular-to-continuum scales of modeling and simulations for single LCP phases, and of their relative benefits and limitations. We likewise recall the sharp versus diffuse interface methods for coupling of two immiscible fluid phases in a hydrodynamic theory. From this assessment, we present a kinetic scale, diffuse interface strategy for hydrodynamic simulations of LCP droplet dispersions. The Fokker–Planck or Smoluchowski equation due to Doi and Hess for the orientational distribution function of the LCP phase is generalized to a two-phase, energy-based theory. Although feasible for simulations by adaptation of existing kinetic solvers, we first put the two-phase kinetic model through analogous preliminary benchmarks that were applied to the Doi–Hess theory for LCPs. We project onto the scalar zeroth moment and tensorial second-moment of the rod number density function to achieve a generalized Landau-deGennes two-phase model for equilibria and imposed shear of LCP droplets in a viscous fluid. A numerical algorithm in two space dimensions is developed and implemented to study global droplet defect structure versus interfacial anchoring energy. Simulations reveal topological defects (surface boojums for tangential anchoring and interior degree 1/2 or radial defects for normal anchoring) and details of their respective cores. These predictions support the hypothesis in [I. Lin et al., Science, 2011, 332, 1297–1300] that anchoring boundary conditions between the LCP and surrounding fluid phase can be satisfied by the formation of extremely localized defect cores which self-organize the orientational order external to the cores, without the need for bend-splay-twist mediated, continuous elastic strain.

Sensitivity is a key factor in the performance of a sensor. To achieve maximum guided-mode resonant optical biosensor sensitivity, a comparison of biosensor sensitivity for Transverse Electric (TE) and Transverse Magnetic (TM) modes based on the distribution of electric fields is presented in this article. A label-free guided-mode resonant optical biosensor is designed using the quarter-wave anti-reflection method to reflect only a narrow band of wavelengths modulated by the adsorption of a biochemical material on the sensor surface at the reflected frequency. With the distribution of electric fields simulated according to the Rigorous Coupled Wave Analysis (RCWA) theory, it is found that the full width at half maximum of the TM mode is (~4 nm) narrower than that of the TE mode (~20 nm), and the surface sensitivity of the TE mode incident light is three times that of the TM mode. It is proposed in this article that the light mode plays an important role in the sensitivity of guided-mode resonant biosensors.

A tunable infrared optical switch based on a plasmonic structure consisting of aluminum nanoarrays with a thin film of vanadium dioxide is proposed. This optical switch can realize arbitrary wavelength-selective optical switching in the mid-infrared region by altering the radii of the aluminum nanoarrays. Furthermore, since vanadium dioxide transforms from its low-temperature insulator phase to a high-temperature metallic phase when heated or applied voltage, the optical switch can achieve two-way switching of its “ON” and “OFF” modes. Finite-difference time-domain software is used to simulate the performance of the proposed infrared optical switch. Simulation results show that the switch offers excellent optical performances, that the modulation depth can reach up to 99.4%, and that the extinction ratio exceeds −22.16 dB. In addition, the phase transition time of vanadium dioxide is on the femtosecond scale, which means that this optical switch based on a vanadium dioxide thin film can be used for ultrafast switching.