Dynamically tunable asymmetric transmission in PT-symmetric metasurfaces

Tapar, J. and Kishen, S. and Emani, N.K. (2021) Dynamically tunable asymmetric transmission in PT-symmetric metasurfaces. In: Active Photonic Platforms XIII, 1 August 2021 through 5 August 2021, San Diego.

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Abstract

The concept of parity-time (PT) symmetry has recently expanded the toolbox to achieve active tunability in metasurfaces by modulating the imaginary part of the refractive index. In this work, we propose a hybridized static-active platform to dynamically tune the intensity and angular response of light by varying the non- Hermiticity factor in an all-dielectric metasurface. We numerically demonstrate tunable asymmetric transmission with respect to gain or loss side incidence in a vertically stacked Mie-resonant GaInP phased-array metasurface. It should be noted that the proposed system is reciprocal despite asymmetric transmission as the materials considered are in a linear regime. The primary building block consists of four PT-symmetric nanopillars of varying radii to achieve sufficient phase sampling. The overall design parameters are optimized for operation at a wavelength of 655 \textitnm (typical PL emission peak of GaInP). For loss side normal incidence, the transmission is predominantly in the 0\textrmth diffraction order (\textitη\textrml\textrm0~ 0:80, \textitη\textrml\textrm1~ 0:18), while for gain side normal incidence, an amplified transmission is in the 1\textrmst order (\textitη\textrmg \textrm0~ 0:02, \textitη\textrmg \textrm1~0:78). The observed asymmetric transmission is due to the near-field coupling between different Mie multipoles, broken in-plane mirror symmetry (meta-atoms with increasing radii along the x-axis), and the broken PT-phase along the propagation direction. An asymmetry factor, ~0:9, is observed at λ = 655 \textitnm. The symmetry in transmission can be restored by reducing the gain-loss contrast. We believe an optimal arrangement of gain-loss resonators combined with tunable pumping (either optically or electrically) could pave the way towards practical reconfigurable metasurfaces.

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IITH Creators:

IITH Creators	ORCiD
Emani, Naresh Kumar	https://orcid.org/0000-0002-0488-921X

Item Type:

Conference or Workshop Item (Paper)

Uncontrolled Keywords:

Active metasurface, Asymmetric transmissions, Dynamic tunability, Metasurface, Paritytime symmetries, Phase gradient, Phase gradient metasurface, Spectral singularities, Tunables

Subjects:

Electrical Engineering

Divisions:

Department of Electrical Engineering

Depositing User:

Mrs Haseena VKKM

Date Deposited:

23 Dec 2021 06:35

Last Modified:

09 Mar 2022 10:41

URI:

http://raiithold.iith.ac.in/id/eprint/9080