Abstract
A one-dimensional photonic crystal (PhC) with termination by a metal film—a plasmonic photonic-crystal slab—has been theoretically analyzed for its optical response at a variation of the dielectric permittivity of an analyte and at a condition simulating the molecular binding event. Visualization of the Bloch surface wave resonance (SWR) was done with the aid of plasmon absorption in a dielectric/metal/dielectric sandwich terminating a PhC. An SWR peak in spectra of such a plasmonic photonic crystal (PPhC) slab comprising a noble or base metal layer was shown to be sensitive to a negligible variation of refractive index of a medium adjoining to the slab. As a consequence, the considered PPhC-based optical sensors exhibited an enhanced sensitivity and a good robustness in comparison with the conventional surface-plasmon and Bloch surface wave sensors. The PPhC biosensors can be of practical importance because the metal layer is protected by a capping dielectric layer from contact with analytes and, consequently, from deterioration.
Highlights
It is noted that highly sensitive, reliable diagnostic approaches are necessary for probing lower abundance proteins in analytes, when detecting diseases at early stages [1,2]
We summarize theoretical results on analysis of the Bloch surface wave excited in plasmonic photonic crystal (PPhC) with termination by a single plasmonic layer of a noble or base metal
To compare performances of PPhC sensors with the surface plasmon resonance (SPR) and conventional surface wave resonance (SWR) counterparts, the maximum of reflectance ∆Rmax was evaluated when searching in a spectral range of 700–1500 nm through D, α and ε′′. (Evaluation for the SPR sensor was done in a spectral range of 700–3000 nm; calculations showed that the maximum response was at λ = 2642 nm and any further increase of the calculation range is not essential.) Figure 3 summarizes data on the performance of the sensors
Summary
It is noted that highly sensitive, reliable diagnostic approaches are necessary for probing lower abundance proteins in analytes, when detecting diseases at early stages [1,2]. Plasmonic photonic-crystals (PPhC) with termination by gold films have been theoretically analyzed for its optical response at a variation of the dielectric permittivity of an analyte [31] and in a situation modeling the event of biomolecular binding [32]. In these works, a sharp attenuation peak associated with SWR has been visualized in p-polarized reflection spectra due to plasmon absorption in gold (the situation where SPR and SWR are excited simultaneously).
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