High-performance dual-wavelength polarization optical switch based on a quasi-rectangular octamer meta-structure comprised of Ag@Au nanorods

Using plasmonic metamaterials in all-optical switches has emerged as a desirable method due to its benefits of having a small footprint and impressive electric field tunability. Herein, a novel, to the best of our knowledge, quasi-rectangular nano-octamer structure comprising eight Ag@Au nanorods is proposed as a dual-wavelength polarization-sensitive all-optical switch with high-modulation depth, excellent extinction ratio, and low insertion loss. The finite element method is employed to investigate the switch performance. Initially, the feasibility of the optical switch is validated by the transmittance spectra. Subsequently, the influence of the structural parameters of the quasi-rectangular nanorod array on transmission spectra and electric field is studied. The working principle of the optical switch is to localize the incident light via horizontal and vertical pairs of nanorods, based on surface plasmon polaritons. Ultimately, the performance of the optical switch is investigated. The relationship between the transmittance of the switch and the polarization angle of the incident light conforms to Malus’s Law. After structure optimization, the optical switch shows extinction ratios of 18.68 and 23.46 dB, insertion losses of 0.16 and 0.67 dB, and modulation depths of 98.645% and 99.550% at 1.42 µm and 1.55 µm, respectively. This study provides a theoretical foundation for the design of tunable dual-wavelength polarization optical switches, which are essential to ultra-compact, ultrafast, and high-capacity all-optical information processing.