Optical properties and enhanced Faraday rotation in three-layer hybrid magneto-plasma crystals with C4h symmetry

Abstract

We investigate the optical properties and magneto-optical (MO) Faraday effect of a type of hybrid magneto-plasma crystal (HMPC) that is composed of a magnetic layer sandwiched between two Ag layers containing an array of holes. It is found that the Faraday rotation is effectively enhanced due to Fabry-Perot resonance and waveguide surface-plasmon (WSP) hybrid mode coupling, respectively, and their peaks are always consistency with the corresponding transmittance peak in position if this structure possesses with C4h symmetry. Moreover, we take the square hole array structure as an example to investigate the characteristics of the transmission and Faraday rotation spectra, and present the dependences of the transmittance, Faraday rotation angle, and figure of merit on structure parameters, such as the size of the square hole, period, and the thickness of the Ag layer. In order to understand the underlying physical mechanism of significantly enhanced Faraday rotation, we analyze the distribution of electric and magnetic fields at the two resonance wavelengths. The results indicate that the enhanced MO Faraday rotation, whose resonant wavelength is almost insensitive to the size of the square hole, is primarily caused by the Fabry-Perot resonance; the other enhanced Faraday rotation, whose resonant wavelength is almost linearly related with the size of the square hole, arises from the coupling effect between WSP hybrid mode existing in square holes of two Ag layers. The results hold significant importance for the development and application of MO devices, and provide valuable insights into the design and optimization of novel MO systems.

Keywords

• Enhanced Faraday rotation
• Fabry-Perot resonance
• Localized surface-plasmon
• Waveguide surface-plasmon
• The finite difference time domain method