Dynamically tunable asymmetric transmission in PT-symmetric metasurfaces

Jinal Tapar; Saurabh Kishen; Naresh Kumar Emani

doi:10.1117/12.2593585

1 August 2021 Dynamically tunable asymmetric transmission in PT-symmetric metasurfaces

Jinal Tapar, Saurabh Kishen, Naresh Kumar Emani

Proceedings Volume 11796, Active Photonic Platforms XIII; 1179617 (2021) https://doi.org/10.1117/12.2593585
Event: SPIE Nanoscience + Engineering, 2021, San Diego, California, United States

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 nm (typical PL emission peak of GaInP). For loss side normal incidence, the transmission is predominantly in the 0^th diffraction order (η^l₀~ 0:80, η^l₁~ 0:18), while for gain side normal incidence, an amplified transmission is in the 1^st order (η^g ₀~ 0:02, η^g ₁~0:78). 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 nm. 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.

Conference Presentation

Citation Download Citation

Jinal Tapar, Saurabh Kishen, and Naresh Kumar Emani "Dynamically tunable asymmetric transmission in PT-symmetric metasurfaces", Proc. SPIE 11796, Active Photonic Platforms XIII, 1179617 (1 August 2021); https://doi.org/10.1117/12.2593585

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