Sub-diffraction thin-film sensing with planar terahertz metamaterials

Withayachumnankul, W. and Lin, Hungyen and Serita, Kazunori and Shah, Charan M. and Sriram, Sharath and Bhaskaran, Madhu and Tonouchi, Masayoshi and Fumeaux, Christophe and Abbott, Derek (2012) Sub-diffraction thin-film sensing with planar terahertz metamaterials. Optics Express, 20 (3). pp. 3345-3352. ISSN 1094-4087

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Planar metamaterials consisting of subwavelength resonators have been recently proposed for thin dielectric film sensing in the terahertz frequency range. Although the thickness of the dielectric film can be very small compared with the wavelength, the required area of sensed material is still determined by the diffraction-limited spot size of the terahertz beam excitation. In this article, terahertz near-field sensing is utilized to reduce the spot size. By positioning the metamaterial sensing platform close to the sub-diffraction terahertz source, the number of excited resonators, and hence minimal film area, are significantly reduced. As an additional advantage, a reduction in the number of excited resonators decreases the inter-cell coupling strength, and consequently the resonance Q factor is remarkably increased. The experimental results show that the resonance Q factor is improved by more than a factor of two compared to the far-field measurement. Moreover, for a film with a thickness of λ/375 the minimal area can be as small as 0.2λ × 0.2λ. The success of this work provides a platform for future metamaterial-based sensors for biomolecular detection.

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Journal Article
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Optics Express
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24 Nov 2015 09:38
Last Modified:
18 Sep 2023 00:56