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Dynamically Tunable Asymmetric Transmission in PT-Symmetric Phase Gradient Metasurface
ACS Photonics ( IF 6.5 ) Pub Date : 2021-11-07 , DOI: 10.1021/acsphotonics.1c01178 Jinal Tapar 1 , Saurabh Kishen 1 , Naresh Kumar Emani 1
ACS Photonics ( IF 6.5 ) Pub Date : 2021-11-07 , DOI: 10.1021/acsphotonics.1c01178 Jinal Tapar 1 , Saurabh Kishen 1 , Naresh Kumar Emani 1
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Active optical metasurfaces have attracted significant research attention in recent times. The conventional thermal and free-carrier induced index-tuning mechanisms have been widely explored to realize dynamic modulation of the optical properties. However, their modulation efficiency is limited by the intrinsic response of functional materials. The recent advances in the concept of PT (parity-time) symmetry and spatiotemporal modulation of permittivity have opened new avenues to realize dynamic tunability. In this work, we propose an all-dielectric PT-symmetric metasurface to tune the intensity and angular response of light through dynamic gain–loss modulation. Our approach shows tunable asymmetric transmission in a vertically stacked Ga0.5In0.5P phased-array metasurface. The overall metasurface is optimized for operation at a wavelength of 655 nm (typical PL emission peak of Ga0.5In0.5P). The transmission is predominantly in the zeroth diffraction order (η0 ∼ 0.80, η1 ∼ 0.18) for loss side normal incidence, and an amplified transmission is observed in the first diffraction order (η0 ∼ 0.04, η1 ∼ 0.79) for gain side incidence. In addition to the asymmetric transmission for normal incidence, the proposed metasurface also exhibits asymmetric amplification in transmission for oblique incidence. An optimal arrangement of gain–loss resonators combined with tunable pumping (either optical or electrical) can pave the way toward on-chip reconfigurable nanophotonic devices.
中文翻译：
PT-对称相位梯度超表面中的动态可调非对称传输
近年来，有源光学超表面引起了广泛的研究关注。传统的热和自由载流子诱导的折射率调节机制已被广泛探索以实现光学特性的动态调制。然而，它们的调制效率受到功能材料固有响应的限制。PT（奇偶时间）对称性和介电常数时空调制概念的最新进展为实现动态可调性开辟了新途径。在这项工作中，我们提出了一种全介电 PT 对称超表面，通过动态增益损耗调制来调整光的强度和角响应。我们的方法显示了垂直堆叠的 Ga 0.5 In 0.5 中的可调非对称传输P 相控阵超表面。整个超表面针对在 655 nm 的波长（Ga 0.5 In 0.5 P 的典型 PL 发射峰）下运行进行了优化。透射主要在损耗侧垂直入射的第零衍射级（η 0 ∼ 0.80, η 1 ∼ 0.18）中，并且在第一衍射级（η 0 ∼ 0.04, η 1∼ 0.79) 增益侧入射。除了垂直入射的非对称透射外，所提出的超表面还表现出斜入射透射的非对称放大。增益损耗谐振器的最佳布置与可调谐泵浦（光学或电学）相结合，可以为片上可重构纳米光子器件铺平道路。
更新日期：2021-11-17
中文翻译：
PT-对称相位梯度超表面中的动态可调非对称传输
近年来，有源光学超表面引起了广泛的研究关注。传统的热和自由载流子诱导的折射率调节机制已被广泛探索以实现光学特性的动态调制。然而，它们的调制效率受到功能材料固有响应的限制。PT（奇偶时间）对称性和介电常数时空调制概念的最新进展为实现动态可调性开辟了新途径。在这项工作中，我们提出了一种全介电 PT 对称超表面，通过动态增益损耗调制来调整光的强度和角响应。我们的方法显示了垂直堆叠的 Ga 0.5 In 0.5 中的可调非对称传输P 相控阵超表面。整个超表面针对在 655 nm 的波长（Ga 0.5 In 0.5 P 的典型 PL 发射峰）下运行进行了优化。透射主要在损耗侧垂直入射的第零衍射级（η 0 ∼ 0.80, η 1 ∼ 0.18）中，并且在第一衍射级（η 0 ∼ 0.04, η 1∼ 0.79) 增益侧入射。除了垂直入射的非对称透射外，所提出的超表面还表现出斜入射透射的非对称放大。增益损耗谐振器的最佳布置与可调谐泵浦（光学或电学）相结合，可以为片上可重构纳米光子器件铺平道路。
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