Optical transmission anomalies in a double-layered metallic slit array.

Area of Science:

• Optics and Photonics
• Metamaterials Science
• Condensed Matter Physics

Background:

• Metamaterials offer unique optical properties not found in natural materials.
• Optical transmittance dips are crucial phenomena for manipulating light.
• Rayleigh-Wood's (RW) anomaly is a known phenomenon in periodic structures.

Purpose of the Study:

• To theoretically predict and experimentally verify an anomalous optical transmittance dip in a double-layered metamaterial.
• To investigate the influence of relative lateral displacement between metallic slabs on the dip frequency.
• To elucidate the underlying mechanism of this anomaly and its relation to RW anomaly.

Main Methods:

• Theoretical prediction of optical transmittance using a double-layered metamaterial model with slit arrays.
• Numerical simulations to analyze the effect of varying lateral displacement (l) on transmittance.
• Experimental verification in the terahertz (THz) region.

Main Results:

• Observed an anomalous optical transmittance dip dependent on the lateral displacement (l) of metallic slabs.
• The dip frequency was tunable and related to the Rayleigh-Wood's (RW) anomaly frequency.
• Theoretical predictions showed good agreement with experimental results in the THz range.

Conclusions:

• The study confirms the existence of a novel anomalous optical transmittance dip in double-layered metamaterials.
• The mechanism involves interference between propagating and evanescent waves, distinct from the standard RW anomaly.
• The RW anomaly can be suppressed under specific displacement conditions (l=0 and l=d/2).