Numerical and experimental analysis of optical response of sub-wavelength period structure in carbonaceous film for refractive index sensing.

The resonance structure coupling the light into the leaky guided modes, which are visible in the reflection spectra as sharp peaks (Wood's anomalies), is analyzed experimentally and numerically. The guided mode resonance structure of 428 nm period patterned in a carbonaceous film demonstrated sensitivity of 70 nm/RIU. The calculated mode diagram explained the nature and positions of the peaks registered experimentally. The reflection spectra, near/far field distributions and field penetration depth for the analyzed structure were simulated employing three numerical solvers. The set of weak Rayleigh's anomalies was indentified from the simulations and the experimental data.