Contactless functional testing of grating-coupled evanescent wave (bio)chemical sensors

The contactless measurement of the sole modulus of the reflection coefficient of a grating-coupled slab waveguide sensor at three definite points of the reflection spectrum gives all necessary information for the determination of the complete set of phenomenological parameters of a waveguide grating (bio)chemical sensor thanks to a physically meaningful representation of the resonant reflection of a free space wave in the form of a circle in the complex plane. This property leads to a simple, non-destructive, wafer-scale functional testing methodology for grating-coupled (bio)chemical sensor chips.