Ultrafast terahertz transmission/group delay switching in photoactive WSe2-functionalized metaphotonic devices

The emergence of larger-scaled two-dimensional (2D) layered materials has attracted intense research efforts and significant progress in the area of photonics and optoelectronics recently. As a remarkable representative of 2D materials, transition metal dichalcogenides (TMDCs) have demonstrated an astonishing photoconductivity and the ultrafast charge carrier dynamics, which provides excellent potentials for ultrafast optical modulators. Herein, by simply transferring a high-quality CVD-grown WSe2 multilayer on plasmon-induced transparency (PIT) metasurfaces, we demonstrate that the transmission amplitude modulation is as high as 43% and the slow light switching is up to 6 ps in the THz regime. Under photoexcitation, both functionalities are dynamically controlled within ~8 ps owing to a merit of ultrafast free carriers’ relaxation in the WSe2 multilayer. Moreover, a theoretical model consisting of two coupled harmonic oscillators and the near-field distributions are simultaneously employed to verify the strong dependence of the active PIT switching behavior on the suppression of the bright mode of split ring resonators. Our proposed versatile active WSe2-functionalized metasurface with a low cost and simple manufacturing will give researchers new insights into the ultrafast switchable metaphotonic devices. A novel WSe2-functionalized metaphotonic device has been explored as an ultrafast terahertz modulator, which processes transmission modulation and slow light switching. A large-scale WSe2 multilayer with sub-picosecond effective photocarriers lifetime is transferred on our proposed plasmon-induced transparency metasurface. The high transmission modulation is as high as 43% and an extraordinary group delay tuning is up to 6 ps. The whole switching-off and -on process of both functionalities is controlled within ~8 ps, allowing for ultrafast modulation speed up to hundreds GHz. This work provides a new path to enrich active tunable metaphotonic devices and the strategy is applicable to other photoactive 2D materials to ignite more innovations across ultrafast optically switching platforms. [Display omitted]