Subwavelength focusing in the infrared range using different metasurfaces

Author's Department

Electronics & Communications Engineering Department

Second Author's Department

Physics Department

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https://iopscience.iop.org/article/10.1088/1402-4896/ab2eb2

All Authors

Manar Abdel-Galil; Yehea Ismail; Mohamed Swillam

Document Type

Research Article

Publication Title

Physica Scripta

Publication Date

1-1-2019

doi

10.1088/1402-4896/ab2eb2

Abstract

In this paper, we introduce three different metasurfaces that can achieve subwavelength focusing of the radiation in the infrared domain. The structures presented achieve high focusing resolution, high transmission efficiency or high mid-infrared bandwidth so they can satisfy the different critical requirements of different infrared applications. We chose the wavelength of 9 μm in the mid-infrared as an example in our designs, yet we showed how the performance of our structures varies across other infrared wavelengths. In building our metasurfaces in the infrared range, we used the phase modulation techniques that proved to be useful in the visible domain. We showed that by choosing the suitable materials and design parameters, the same phase modulation concepts that were useful in the visible range can also be used to achieve focusing in the infrared range. In our infrared designs and for the wavelength of 9 μm, the best focusing resolution achieved is 0.5λ in the first introduced metasurface while the best transmission efficiency achieved exceeds 60% in the third metasurface. The highest bandwidth attained among the introduced metasurfaces is 7-20 μm in case of the second structure. For infrared wavelengths other than 9 μm, the focusing resolution could reach down to 0.49λ at the wavelength of 20 μm in case of the second structure and the transmission efficiency could reach up to roughly 74% at all wavelengths between 17 μm and 20 μm in case of the third structure. The used materials are copper and silicon, which are specifically suitable for the infrared range besides being CMOS compatible and relatively inexpensive. The proposed metasurfaces can be integrated in infrared applications such as biosensors, infrared miniaturized spectrometers, thermal photovoltaic cells, and heat harvesting. Each proposed metasurface can serve in a different infrared application according to the critical requirement of the application itself whether it is a better focusing performance or a high transmission efficiency or even a wider mid-infrared bandwidth.

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