Floquet parity-time symmetry in integrated photonics

• Published in: Nature communications Vol. 15; no. 1; pp. 946 - 7
• Main Authors: Liu, Weijie, Liu, Quancheng, Ni, Xiang, Jia, Yuechen, Ziegler, Klaus, Alù, Andrea, Chen, Feng
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 31.01.2024; Nature Publishing Group; Nature Portfolio
• Subjects: 639/624/1075/1080; 639/624/400/1021; 639/766/1130/2799; Amplification; Broken symmetry; Gain-Loss; Humanities and Social Sciences; multidisciplinary; Parity; Photonics; Science; Science (multidisciplinary); Symmetry; Waveguides
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-45226-x

Parity-time (PT) symmetry has been unveiling new photonic regimes in non-Hermitian systems, with opportunities for lasing, sensing and enhanced light-matter interactions. The most exotic responses emerge at the exceptional point (EP) and in the broken PT-symmetry phase, yet in conventional PT-symmetric systems these regimes require large levels of gain and loss, posing remarkable challenges in practical settings. Floquet PT-symmetry, which may be realized by periodically flipping the effective gain/loss distribution in time, can relax these requirements and tailor the EP and PT-symmetry phases through the modulation period. Here, we explore Floquet PT-symmetry in an integrated photonic waveguide platform, in which the role of time is replaced by the propagation direction. We experimentally demonstrate spontaneous PT-symmetry breaking at small gain/loss levels and efficient control of amplification and suppression through the excitation ports. Our work introduces the advantages of Floquet PT-symmetry in a practical integrated photonic setting, enabling a powerful platform to observe PT-symmetric phenomena and leverage their extreme features, with applications in nanophotonics, coherent control of nanoscale light amplification and routing. Here the authors unveil an approach rooted in non-Hermitian physics to precisely control light amplification in an integrated photonic platform, paving the way for innovative on-chip functionalities, like coherent control of light amplification and routing.