Showing posts with label J. Y. Park. Show all posts
Showing posts with label J. Y. Park. Show all posts

Wednesday, June 23, 2021

Abstract-Detection of microorganisms using terahertz metamaterials

 


S. J. Park, J. T. Hong, S. J. Choi, H. S. Kim, W. K. Park, S. T. Han, J. Y. Park, S. Lee, D. S. Kim, Y. H. Ahn 


https://www.nature.com/articles/srep04988?proof=t

Microorganisms such as fungi and bacteria cause many human diseases and therefore rapid and accurate identification of these substances is essential for effective treatment and prevention of further infections. In particular, contemporary microbial detection technique is limited by the low detection speed which usually extends over a couple of days. Here we demonstrate that metamaterials operating in the terahertz frequency range shows promising potential for use in fabricating the highly sensitive and selective microbial sensors that are capable of high-speed on-site detection of microorganisms in both ambient and aqueous environments. We were able to detect extremely small amounts of the microorganisms, because their sizes are on the same scale as the micro-gaps of the terahertz metamaterials. The resonant frequency shift of the metamaterials was investigated in terms of the number density and the dielectric constants of the microorganisms, which was successfully interpreted by the change in the effective dielectric constant of a gap area.

Sunday, November 10, 2019

Abstract-Tunable broadband terahertz polarizer using graphene-metal hybrid metasurface




K. Meng, S. J. Park, L. H. Li, D. R. Bacon, L. Chen, K. Chae, J. Y. Park, A. D. Burnett, E. H. Linfield, A. G. Davies, and J. E. Cunningham

 (a) Schematic diagram of the graphene-metal hybrid wire grid structure. Upper figure: cross-section of the array, lower figure: top view of the array. (b) Schematic diagram of the THz transmission experiment: the lower electrode was used for applying gate voltage and the upper two electrodes were connected to a source meter for measuring the conductivity (indicated by G) (c) DC conductivities of graphene in each device as a function of gate voltage. (d) SEM image of the graphene-metal hybrid wire grids with ΛM/G=30μm. (e) Raman spectrum of the graphene in a typical device.


https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-23-33768

We demonstrate an electrically tunable polarizer for terahertz (THz) frequency electromagnetic waves formed from a hybrid graphene-metal metasurface. Broadband (>3 THz) polarization-dependent modulation of THz transmission is demonstrated as a function of the graphene conductivity for various wire grid geometries, each tuned by gating using an overlaid ion gel. We show a strong enhancement of modulation (up to ∼17 times) compared to graphene wire grids in the frequency range of 0.2–2.5 THz upon introduction of the metallic elements. Theoretical calculations, considering both plasmonic coupling and Drude absorption, are in good agreement with our experimental findings.
Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Saturday, November 2, 2013

Abstract-Frequency downshift of Nd:YAG lasers and terahertz radiation






S. Son, Sung Joon Moon, and J. Y. Park  »View Author Affiliations

Optics Letters, Vol. 38, Issue 22, pp. 4578-4580 (2013)
http://dx.doi.org/10.1364/OL.38.004578




The interaction between an intense laser and a cotraveling relativistic dense electron beam could result in the downshifting of the laser frequency. It is theoretically analyzed that this process can generate a coherent terahertz radiation. The radiation energy could reach the order of 1 mJ per shot in the duration of 100 ps, or a temporal radiation power of 10 MW, with a set of practically relevant parameters.
© 2013 Optical Society of America