Plasmonic Interference in Superstructured Metal Photonic Crystals

Surface plasma waves (SPWs) excited by illumination of 2-dimensional superstructured metal photonic crystals (SMPCs) are investigated with extraordinary optical transmission (EOT). An m × m lattice of holes ( m = 3 with the period p of 3 μm) fabricated in an Au film atop a GaAs substrate (refractive index n d ), referred to as a basis plasmonic antenna (BPA), forms an SMPC that consists of 24 × 24 BPAs with varying spacing between BPAs, d . Two categories of d are examined: κ = d / p = i ( i an integer), where SPWs generated at each BPA interfere constructively and κ ≠ i (<1), where the interference leads to drastic changes in the EOT. In the first category, the EOT associated with the fundamental SPW wavelength, T 1, decreases with increasing κ, but has an almost invariant peak wavelength, λ 1, at ∼10.1 μm (≅ n d p ), as expected. In the second category, however, the λ 1 for the dominant EOT peak clearly shows a red-shift to ∼12 μm with T 1 reduced to ∼0 at κ = 0.5, and T 1 has a damped oscillatory dependence on κ. The shift implies strong plasmonic interference between BPAs that follows ∼ n d p ( m + κ)/ H with the integral harmonic order of the Fourier transform of the SMPC, H . This rescaling of the geometric pattern, incommensurate to the BPA period, accompanies the EOT degraded with the dipole deviation from individual holes that provides important relations for the crosstalk among antennas in plasmonic circuits.