Azimuthal illumination enabled ultra-high polar angle sensitivity by a Bloch surface wave resonance refractive index sensor

The scheme of a polar angle space refractive index (RI) sensor based on grating-coupled Bloch surface wave (BSW) resonance excited by azimuthal illuminations is studied. It is shown that, for any polar angle, one can always find a case of BSW resonance with the tangential wave vector of the BSW mode perpendicular to that of the incident electromagnetic wave. When the sensor is designed to work around this BSW resonance, ultra-high polar angle sensitivity can be expected. The numerical simulated polar angle sensitivity reaches as large as 1786 degrees per RI unit (Deg/RIU), which is almost one order higher than that found in the literature. (paper)