Guided Bloch surface wave resonance by near normal and near in-plane illuminations: the hyper azimuthal sensitivity

Refractive index sensors based on the interrogation of guided Bloch surface wave resonance (GBR) in the azimuthal angle domain are studied both theoretically and numerically. The azimuthal sensitivity of the sensors is shown to be inversely proportional to the sines of both the azimuthal angle and the polar angle of the detecting electromagnetic signals. Extremely large azimuthal sensitivity is then achieved when the GBR sensor is designed to work near a small azimuthal angle and the polar angle is also fixed to a small one (For the azimuthal angle domain near φ = 5° and a fixed polar angle of θ = 5°, the azimuthal sensitivity gets larger than 5000 degrees per refractive index unit (Deg/RIU)).