Effect of polarization on dual-band infrared metamaterial emitters or absorbers

• Magnetic polaritons and polarization effect for two metamaterial designs were studied.
• Both designs contain a dielectric film sandwiched between a periodic nanostructure and a ground plane.
• It was found that the absorptance of the double-rectangle pattern is independent of polarization but the local field does.
• The polarization-dependence for the L-shape pattern was elucidated by near-field coupling.
• FDTD was used to perform rigorous simulations and LC circuit models were developed to explain magnetic resonances

This work deals with the spectral radiative properties of metamaterials made of a 2D metallic pattern on a dielectric thin film that separates the top periodic structure from a metal ground plane. Two distinct patterns are considered: one consists of disconnected double-rectangle gold pattern and the other is made of L-shape pattern. Both structures exhibit dual-band emission or absorption peaks in the infrared region. Unlike the disconnected rectangular pattern for which the normal emittance is independent of the polarization angle, the L-shape structure shows strong polarization dependent due to near-field coupling. The electromagnetic fields at the resonant frequencies are analyzed using the finite-difference time-domain technique to elucidate the physical mechanisms accounting for the different behaviors. For both structures, the resonance mechanisms can be explained by magnetic polaritons. Inductor–capacitor circuit models are developed to quantitatively predict the resonance frequencies. This work helps the understanding of polarization dependence in metamaterials and may facilitate their applications in biosensing and infrared spectroscopic system.