A Surface Plasmon Resonance (SPR) biosensor that operates deep into the infrared (3-11 μm wavelengths) is potentially
capable of biomolecule recognition based both on selective binding and on characteristic vibrational modes. A goal is to
operate specifically at wavelengths where biological analytes are strongly differentiated by their IR absorption spectra
and where the refractive index is increased by dispersion. This will provide enhanced sensitivity and selectivity, when
biological analytes bind reversibly to biomolecular recognition elements attached to the sensor surface. This paper
describes work on the optical and materials aspects of IR surface plasmon resonances. First, three possible coupling
schemes are considered: hemicylindrical prisms, triangular prisms, and gratings. Second, materials with plasma
frequencies one order of magnitude smaller than for noble metals are considered, including doped semiconductors and
semimetals.
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