Figure 4
From: Directly patterned substrate-free plasmonic “nanograter” structures with unusual Fano resonances
Fano resonances from MH-VSRRs in mid-infrared. (a, b), measured and calculated transmission spectra of the MH-VSRRs under normal - incidence with the electric field polarized along the y-direction and parameters of l = 0.9 µm, w = 250 nm, ax = ay = 2.0 µm and px = py = 3.0 µm. The gray spectral region at approximately 4.2 µm is a high-absorption region from CO2 in the FTIR chamber. (c) The wavelength of the low-order resonance dip as a function of the empirical length (EL, defined as EL = h + (ax-l)/ 2 + ay/ 2). (d, e), Simulated current distributions of the sample at the low-order and high-order resonance dips in b with h = 1.48 µm. The 3D current flow routes are schematically indicated by the arrows. The amplitude distributions of the electric field in the xz and xy planes are plotted below the corresponding plot of the current distributions. The monitored xz and xy planes are 5 nm away from the front surface of the MHs and the top surface of the VSRRs, respectively. The number in each figure indicates the maximum value of the electric field enhancement.
