| 研究実績の概要 |
The project purpose is to demonstrate a small-size and low-cost sensor for biomarkers using confined surface plasmons in nano-cavities.
We clarified the mechanism of light confinement in the nano-cavities and applied this knowledge to the nano-cavity design for biomaterial sensing. The mechanism of light trapping in the nano-cavities was described in Advanced Optical Materials, 2, 522, 2014. We show that light is confined in the nano-cavities by coupling plasmonic modes to scalable cavity modes and, therefore, the resonance of the nano-cavites can be controlled by varying the geometrical parameters of the cavities. This property enables tuning of the nano-cavity resonance wavelength in the near infrared region in which detection of biomaterials is most efficient. We fabricated the designed nanocavities and obtained a good agreement between the simulated and the fabricated nano-cavities. The sensitivity of the proposed U-shaped nano-cavities was quantified in terms of the shift in the resonance wavelength. The change in the wavelength of the resonance reflectance dip of the nano-cavities was first investigated by varying the refractive index of the cavity surrounding. Moreover, the ability of the nano-cavities to detect biomarkers was tested using a protein ligand scheme by observing the change in the resonance wavelength upon the selective attachment of proteins on the cavity surfaces. Finally a design enabling low-cost fabrication of the sensitive cavity structure was proposed, tested and published in Applied Physics Letters, 105, 061112, 2014.
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