Development of Surface Plasmon Resonance Immuno-Sensors at Mid-Infrared Range

This paper reports the design analysis of a novel doped-silicon infrared-surface plasmon resonance (IR-SPR) platform. The structure combines the advantages of both conventional grating and prism surface plasmon couplers while providing several intrinsic beneficial aspects. In combination with a Fourier transform infrared spectrometer, the biosensor is shown to compare favorably in trace analyte detection with visible range SPR devices while still maintaining the advantageous characteristics of IR-SPR. A numeric analysis of the structure was completed using a rigorous coupled wave analysis method to determine the geometric parameters of the diffraction grating as well as assess the sensor’s performance. Finite element analysis simulations were used to model the electromagnetic field distributions during the plasmon resonance. The results demonstrate that surface binding concentrations of biochemical species as small as 70 pg/mm² can be measured. The large probing depth resulting from the IR spectrum facilitates the study of larger analyte (e.g. living cells). Additionally, the structure offers unequaled adaptability for a user’s specific biosensing needs while remaining inexpensive owing to the microelectromechanical systems (MEMS) batch protocols used in fabrication.