Enhanced Optical Bistability by Coupling Effects in Magnetic Metamaterials

Abstract

Magnetic resonance (MR) based on the metal-insulator-metal (MIM) metamaterial is suitable for optical bistability, since its configuration forms an efficient feedback system. However, the local electric field of MR is too weak to support an intensive optical nonlinearity. In this work, coupling effects between the MR and the propagating surface plasmon resonance (PSPR) are introduced. By manipulating the period p , PSPR approaches and couples to MR, leading to a factor of average electric field enhancement $\vert$ E $_{\rm {avg}}$ /E $_{\rm {inc}}$ $\vert$ $^2$ for MR to be 554.5 at p = 900 nm. Moreover, this period optimizes the reflectance to be nearly zero, and the full-width-half-maximum (FWHM) to be among the narrowest. The optical bistability of the proposed magnetic metamaterial is thus numerically investigated by both its frequency domain response and time domain response. Switch thresholds of I $_{\text{ON-OFF}}$ and I $_{\text{OFF-ON}}$ are 95.8 kW/cm $^2$ and 66.9 kW/cm $^2$ , respectively, which are more than one order of magnitude lower than those without coupling. The on/off ratios are $>$ 4.7. The influence of the incident angle is studied as well. Our proposed concept paves the way for future engineering of miniaturized all-optical switches and modulators, which are core components in optical communication.