2014 Fiscal Year Annual Research Report
高アスペクト比キャビティ内への閉じ込め効果を用いた高感度バイオマーカー検出手法
| Project/Area Number |
14J09884
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| Research Institution | The University of Tokyo |
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Principal Investigator |
何 亜倫 東京大学, 工学系研究科, 特別研究員(DC2)
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| Project Period (FY) |
2014-04-25 – 2016-03-31
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| Keywords | Plasmonics / Nanophotonics / Nanocavities / Nanofabrication / Optical vortices |
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| Outline of Annual Research Achievements |
Plasmonic structures have been used to manipulate light in the subwavelength regime and obtain strong confinement of electric fields in hot spots. The high sensitivity to minute change in the surroundings of these hot spots has led to many successful sensing applications. A major challenge remains in devising plasmonic structures supporting tunable, strong, and sharp resonances with extended surfaces. We report the coupling of ridge hot spots with a scalable resonant U-cavity, in which light is fully trapped in intense optical vortices and confined on the extended cavity surfaces, generating strong and sharp resonances with full width at half maximum as small as 14 nm. Tunable resonance wavelength over a wide range of wavelengths from visible to near-infrared is achieved by controlling the cavity dimensions. Sensing performance with a figure of merit of 136 is attained and biosensing in a protein-ligand scheme is demonstrated by the detection of avidin-biotin complex binding.The proposed U-cavity enables the systematic control of the resonance wavelength due to the property of the cavity, thus widening the range of applications from the visible to the NIR regions. Furthermore, the light trapping effect in U-cavities permits designs based on a finite number of cavities within a few micrometers instead of the conventional infinite arrays. Therefore, the U-cavity structure can be said offer new possibilities to integrate detectors in a variety of micro-systems.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
Plasmonic U-cavity structures formed by 3D nanofins have been developed and applied for chemical sensing and biosensing realizing high sensitivity and among largest figure of merit (FOM). The proposed plasmonic structures are different from the existing structures in that they are hollow and 3D structures, thus the standing-wave resonances in vertical (nanofin plane) and horizontal direction (the perpendicular plane to the nanofins) are exited and coupled. This coupling of surface plasmons and nanofin-cavities realizes new optical properties including loop optical flows for light reflectance and vortex optical flows for light trapping, which are reported for the first time in this research with superior performances.
The fabrication of high-aspect-ratio (height and period was about 850 nm, and width was 70 nm) vertical nanofin structure has been successfully demonstrated. In contrast to standard two-dimensional nanostructures patterned on a substrate, the three-dimensional nanostructures require well-designed and integrated fabrication process. The complete fabrication process includes electron beam lithography, reactive ion etching, inductively coupled plasma etching, ion milling etching, and conformal sputtering.
In this year, four papers have been published in well-known journals. One of the publications was accepted in Advanced Optical Materials, a leading journal in optical field. This publication in Advanced Optical Materials was selected as “Best of Advanced Optical Materials - 2014 edition” by the Journal Editors.
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| Strategy for Future Research Activity |
We are continuously working on a new nanofin cavity structures for different optical applications. A suspended nanofin-cavity structure consisting of metal-coated nanofins is designed. Due to the coupling of plasmonic hot spots to the nanofin cavities, light loop-turns with strong optical flows in the nanofin cavities and the optical properties of the nanofin-cavity structure change from being highly transparent to highly reflective at the resonance wavelength. Therefore, strong and tunable reflected resonance peaks are realized in a very wide range from the NIR to IR region optical filtering. This characteristic is different from most band-pass filters based on light transmission. When the nanofin-cavity is further coupled to the propagating surface plasmon resonance (SPR), a strong and narrow-band reflectance resonance due to the stringent condition of SPR arises with a bandwidth having a FWHM of 92 nm and a Q factor as large as 60 in the IR region. The tunability of the reflectance band is obtained by varying the period of the suspended nanofin cavities, thus tunability can be fully realized using MEMS technology. Furthermore, the high angle-dependence is realized due to coupling the nanofin-cavities to propagating SPR. Reflectance can be controlled from 55% to 9% by varying the incident angle within only 2°. The characteristics of the nanofin-cavity structure provide new solutions to design band-pass filters, optical switches, sensor, and applications in the molecular fingerprint region. The results of this work will also be published in the leading journals.
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Research Products
(7 results)
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[Patent(Industrial Property Rights)] 光学フィルタ2015
Inventor(s)
Y.-L. Ho, J.-J. Delaunay
Industrial Property Rights Holder
Y.-L. Ho, J.-J. Delaunay
Industrial Property Rights Type
特許
Industrial Property Number
2015-008719
Filing Date
2015-01-20
