Abstract
An optical sensor based on the coupling between the plasmonic and photonic resonance modes in metallic photonic crystals is investigated. Large-area metallic photonic crystals consisting of periodically arranged gold nanostructures with dimensions down to sub-100 nm are fabricated using solution-processible gold nanoparticles in combination with interference lithography or interference ablation, which introduces a variety of fabrication techniques for the construction of this kind of sensor device. Sensitivity of the plasmonic response of the gold nanostructures to the changes in the environmental refractive index is enhanced through the coupling between the narrow-band photonic resonance mode and the relatively broad-band plasmon resonance, which is recognized as a Fano-like effect and is utilized to explore sensors. Theoretical modeling shows the characterization and the optimization of the sensitivity of this kind of sensor device. Theoretical and experimental results are demonstrated for the approaches to improve the sensitivity of the sensor device.
Highlights
Localized surface plasmon resonance (LSPR) or particle plasmon resonance (PPR) results from a kind of collective oscillation of the free electrons in metallic nanostructures, which leads to strong scattering and absorption of light and is generally characterized by optical extinction spectroscopy
Waveguided metallic photonic crystals consist of periodically arranged metallic nanostructures on top of a transparent waveguide layer, where gold is usually employed to construct the metallic nanograting structures and inorganic thin films are usually used as the waveguide
Very clean gold nanostructure can be obtained after the annealing process, as can be seen in Figure 4(b) and no additional materials like the remaining substance from the master grating will disturb the interaction between bio-molecules and the gold nanostructures
Summary
Localized surface plasmon resonance (LSPR) or particle plasmon resonance (PPR) results from a kind of collective oscillation of the free electrons in metallic nanostructures, which leads to strong scattering and absorption of light and is generally characterized by optical extinction spectroscopy. The narrow-band WGS resonance mode cuts into the broad-band PPR mode, leaving steep falling and rising edges on both sides of the WGS resonance mode This Fano-like effect [19] in the photonic-plasmonic coupling amplifies the spectroscopic response of PPR to the environmental change in refractive index and enhances the sensitivity of the sensor device. This has been verified experimentally in the detection of specific bioreactions [20]. We introduce new mechanisms that may be utilized to further enhance the sensitivity of the sensor by narrowing the spectrum of the coupled mode through thinning the waveguide layer or by steepening the spectral edge of the coupled mode through optimizing the angle of incidence
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