Imaging biosensor based on planar optical waveguide

A biosensing technique with a two-dimensional spatial resolution based on a planar optical waveguide is presented. The thickness of the waveguide is chosen such that the wavelength of the waveguide mode is located between the maxima of the blue and green pixels of a color camera. A prism based Kretschmann-like configuration is used for waveguide excitation. The prism is placed between crossed polarizers to obtain the waveguide resonance peak. The spectral shift of the resonance peak is determined through the normalized differences in intensities of the blue and green pixels at each point of the color camera. The spatial distribution of resonance wavelength shifts across the camera reflects the spatial distribution of changes in the thickness of the adsorbate over the sample. The sensitivity, dynamic range, and simplicity of practical implementation of this biosensor are compared with those of an imaging biosensor based on photonic crystal surface mode.