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Dynamically tunable asymmetric transmission in PT-symmetric metasurfaces
J. Tapar, S. Kishen,
Published in SPIE
2021
Volume: 11796
   
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 0th diffraction order (ηl0∼ 0:80, ηl1∼ 0:18), while for gain side normal incidence, an amplified transmission is in the 1st order (ηg0∼ 0:02, ηg1∼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. © 2021 SPIE.
About the journal
JournalData powered by TypesetProceedings of SPIE - The International Society for Optical Engineering
PublisherData powered by TypesetSPIE
ISSN0277786X