Sensing concept based on Bloch surface waves and wavelength interrogation.

We report on a new, to the best of our knowledge, sensing concept based on Bloch surface waves (BSWs) and wavelength interrogation that utilizes the interference of $ s $s- and $ p $p-polarized waves from a one-dimensional photonic crystal (1DPhC), represented by a multilayer structure comprising a glass substrate and four bilayers of $ {{\rm TiO}_2}/{{\rm SiO}_2} $TiO/SiO with a termination layer of $ {{\rm TiO}_2} $TiO. We show that when a standard approach based on measurement of the reflectance of a $ p $p- or $ s $s-polarized wave in the Kretschmann configuration fails to confirm the excitation of the BSW, a new approach is successful. We demonstrate that the BSW excitation shows up as a dip with maximum depth, and resonance thus obtained is comparable in magnitude with resonance commonly exhibited by surface plasmon resonance (SPR). The new sensing concept is verified experimentally for ethanol vapors. The BSW resonances are resolved within two band gaps of the 1DPhC with sensitivities of 3272 nm/RIU and 1403 nm/RIU, and figures of merit of $ 43.7 ;{{\rm RIU}^{ - 1}} $43.7RIU and $ 173.2 ;{{\rm RIU}^{ - 1}} $173.2RIU, respectively. This research, to the best of the authors' knowledge, is the first demonstration of a new SPR-like response that can be utilized in a wide range of sensing applications.