2016 Fiscal Year Research-status Report
Development of three-dimensional terahertz photonic chip for molecular sensing
| Project/Area Number |
16K17525
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| Research Institution | University of Tsukuba |
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Principal Investigator |
You Borwen (游博文) 筑波大学, 数理物質系, 助教 (90760736)
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| Project Period (FY) |
2016-04-01 – 2019-03-31
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| Keywords | Sensors / Metamaterials / Waveguides / Terahertz waves / Spectroscopy |
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| Outline of Annual Research Achievements |
The research applies terahertz (THz) photon to sense the molecules because of the energy matching to the intermolecular attraction energy. Based on the designed 3D microstructures, interaction of THz photons and analyte molecules can be realized on a miniaturized chip with high sensitivity. The research purpose is to explore one 3D microstructure, possessing multiple functions of a low-loss waveguide. In the first year of the project, we investigate the THz artificial material based on integrated metal-rod-array (MRA) for phase sensitive fluid detection. The MRA structural period is 0.62 mm, where the diameter and interspace of metal rods are approximately 0.16 and 0.46 mm, respectively. The length of each rod is almost consistent (approximately 1 mm), and the structural total width along the x-axis is 12 periods. Such uniform MRA structure is originally prepared from the rectangular array of polymer rods via microstereolithography, and then the polymer rods are deposited with a 100 nm-thick aluminum metal film via a sputter coating process. We have experimentally demonstrated a MRA-based THz artificial material to transport the TE waves resulted from the resonance among rod slits. The three-layered MRA is suggested as the optimal waveguide sensing length because of the sufficiently long OPL, adequate transmission power and high overlapping field to enhance the wave-analyte interaction.
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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
A terahertz artificial material composed of metal rod array is experimentally investigated on its transmission spectral property and successfully incorporated into microfluidics as a miniaturized terahertz waveguide with an extended optical-path-length for label-free fluidic sensing. Theoretical and experimental characterizations of terahertz transmission spectra show that the wave guidance along the metal rod array originates from the resonance of transverse-electric-polarized waves within the metal rod slits. The extended optical path length along three layers of metal-rod-array enables terahertz waves sufficiently overlapping the fluid molecules embedded among the rods, leading to strongly enhanced phase change by approximately one order of magnitude compared with the blank metal-parallel-plate waveguide. Based on the enhanced phase sensitivity, three kinds of colorless liquid analytes, namely, acetone, methanol, and ethanol, with different dipole moments are identified in situ using the metal-rod-array-based microfluidic sensor. The detection limit in molecular amounts of a liquid analyte is experimentally demonstrated to be less than 0.1 mmol, corresponding to 2.7 μmol per millimeter square area. The phase sensitive terahertz metal-rod-array-based sensor potentially has good adaptability in lab-chip technology for various practical applications, such as industrial toxic fluid detection and medical breath inspection.
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| Strategy for Future Research Activity |
Terahertz waveguiding mechanism of the metal rod array, used as a plasmonic metamaterial, is studied in the 1st year of the project. To further perform the fundamental of the metal rod array to guide terahertz waves, we will continuously discuss its photonic crystal waveguide properties in the 2nd year, including the transmission spectrum, attenuation, and the evanescent field confinement. To completely investigate this 3D-microsctructural metal rod array, its complementary structure, i.e., a metal hole array, is additionally studied.
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