Harnessing anti-parity-time phase transition in coupled topological photonic valley waveguides

Topological and non-Hermitian physics provide powerful tools for manipulating light in different ways. Recently, intense studies have converged on the interplay between topology and non-Hermiticity, and have produced fruitful results in various photonic settings. Currently, the realization of this interplay falls under the paradigm of enabling energy exchange between topological systems and the environment. Beyond this paradigm, it is revealed that a non-Hermitian phenomenon, i.e., the anti-parity-time phase transition, naturally emerges from a Hermitian system realized by coupled topological valley waveguides. Such phase transition gives two exotic topological superstates in the spectral domain. By further combining the two phases with topological robustness, a photonic topological bi-functional device is realized on a silicon-on-insulator platform at telecommunications frequencies. The results provide a new perspective on light manipulation and integrated device applications.This work was supported by the National Key Research and Development Program of China under Grants no. 2022YFA1404902, 2022YFA1404704, 2022YFA1405200 and 2019YFB2203002, the National Natural Science Foundation of China (NNSFC) under grant no. 62171406, 11961141010, 61975176, 91950204, 61975177, and U20A20164, the Zhejiang Provincial Natural Science Foundation under grants no. Z20F010018, the Key Research and Development Program of Zhejiang Province under grant no. 2022C01036, and the Fundamental Research Funds for the Central Universities

High-Speed Compact Plasmonic-PdSe₂ Waveguide-Integrated Photodetector

Waveguide-integrated photodetectors are essential components in integrated photonic circuits since they facilitate light conversion into electrical signals. Nonetheless, optical absorption and carrier collection can significantly affect the device performance. As a solution to this issue, plasmonic slot waveguides confine optical energy within a subwavelength scale in a photoconductive detector, enhancing optical absorption and providing extremely short channels to collect carriers. Two-dimensional van der Waals layered palladium selenide (PdSe2) exhibits the merits of a narrow bandgap and high carrier mobility, thus positioning it as a favorable candidate material for photodetectors operating at the telecommunication band. In this study, we propose and experimentally verify a high-speed PdSe2-plasmonic waveguide-integrated photodetector with a dark current of 4.5 μA and an intrinsic responsivity of 560.1 mA·W−1 at 3 V. Additionally, it has an internal quantum efficiency of 32.3%, and the measured 3 dB bandwidth is 17.5 GHz. This integrated photodetector fulfills the requirements of various critical applications in optical communication, microwave photonics, sensing, and imaging