Enhancement of light-matter interaction using surface states in photonic crystal structures

Bloch Surface Waves (BSWs) are propagation modes that exist at the interface between a homogeneous medium and a photonic crystal (PhC). The confinement at the interface of the media relies on total internal reflection in the homogeneous medium and on the photonic band gap in the PhC. The dispersion relation of BSWs can be easily tailored through the design of the PhC. This makes BSWs extremely flexible and suitable for applications in the field of optical sensors, light emitters, and photovoltaic devices, where the capability to confine and amplify the electromagnetic field in micro-and nano-structures allows for the enhancement of the light-matter interaction. In particular, we present two different configurations for the detection of Bloch surface waves in silicon nitride multilayers: attenuated total reflectance and photoluminescence measurements. In the first, we measured a 50-fold enhancement of the diffraction signal by a protein grating printed on the multilayer when the incident light beam is coupled to the surface waves. In the second, we observe a significant modification of the spontaneous emission by a monolayer of rhodamine molecules bonded to the photonic crystal surface. These results may found application in the field of optical sensors, particularly for biosensing.