Year-end Sale % OFF 
Abstract
Plasmon-based devices are powerful for use in highly sensitive evanescent-field detection and analysis, but they exhibit the problem of limited frequency tunability for fixed structures. This feature causes problems in the multi-frequency investigations required for materials characterization, bio-related research, etc. Here, we propose and fabricate a spiral-shaped plasmonic structure that enables a continuous frequency-tuneable evanescent-field concentration in the terahertz (THz) region with simple operation. The device also increases the electric field intensity at the subwavelength aperture, thus significantly amplifying the transmission. Highly tuneable transmission bands are observed by simply rotating the spiral plasmonic structure, which are in good agreement with the behaviour expected from electromagnetic simulation. Medical examinations are performed by measuring the interactions between the frequency-tuneable plasmons and bio-samples, which enables observing distinct tissue-dependent transmission spectra and images. The developed device simultaneously offers the advantages of both plasmonic devices and frequency-tuneable devices, which can increase the availability and versatility of evanescent-field THz sensing and analysis. The mechanism presented will shed light on THz plasmonics and motivate the implementation of a variety of applications based on plasmon-mediated THz technologies.
Highlights
The use of subwavelength apertures together with surface modification to generate high electromagnetic wave transmission and an extraordinary electric field concentration provides one possible solution to these problems[8,9,10,11,12,13]
We demonstrated that in the spiral bull’s eye (SBE) structure, the frequency of the THz transmission peak can be tuned according to the angle of polarization (AoP) of the incident THz wave relative to the surface of the SBE structure
We expect that the developed spiral plasmonic structures can be applied to arbitrarily tuneable THz plasmonic devices and will promote applications that require multi-frequency investigations, such as medical examination, molecular research, and materials and device characterization
Summary
Plasmon-based devices are powerful for use in highly sensitive evanescent-field detection and analysis, but they exhibit the problem of limited frequency tunability for fixed structures. To further improve the surface electric field concentration at the aperture of the SBE structure and induce multi-frequency coupling, a Siemens-star aperture (Fig. 1(b)) was used instead of the conventional circular subwavelength aperture Special aperture shapes, such as a bow-tie aperture with sharp tips, have previously been shown to exhibit highly increased electric fields near the tips[20]. The THz mapping of mouse-tail transverse sections further verified that the SBE can be used to realize high-contrast, frequency-selective measurements with high THz field concentration This structure can be modified to fit most frequency ranges for SSP generation by changing the period and depth of the grooves[18], and is, potentially useful for future wide-band, frequency-selective THz applications including nanomaterials characterization, chemical spectroscopy, and biological analysis. The capability of circularly polarized THz field concentration and enhancement provides an interesting possibility of investigating spin dynamics of magnetic materials, chiralities of optical isomers, etc
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
