Spectroscopic Evidence of Bloch Surface Waves in the Mid Infrared

Bloch Surface Waves are surface electromagnetic waves with very low intrinsic losses, existing in both in-plane and out-of plane polarizations, supported by a one-dimensional photonic crystal with an in-gap defect. We have developed thin-film deposition technology on CaF prisms suitable for biosensing applications of BSWs in the mid-infrared. Here we report spectroscopic evidence of BSWs, in perfect agreement with theory, in the wavelength range from 4 to 6 micrometers.