Anapole-state-enhanced 2D chiral photodetector operating in the near-infrared second window.

Abstract

Two-dimensional (2D) materials hold promise for miniaturized photodetectors. With ample exciton resonances, the photodetection range of transition metal dichalcogenides (TMDCs) can be further extended to long wavelengths on a large scale by two-photon absorption (TPA), breaking the limit of their bandgaps. However, the conversion efficiency of TPA usually remains low despite resonant nonlinear optical effects. Here, we present a plasmonic metasurface-enhanced 2D TMDC photodetector by means of high-order multipoles with anapole states, as well as quasi-bound states in the continuum, operating efficiently in the near-infrared second (NIR-Ⅱ) window at room temperature. The optical response of the MoS₂/WSe₂ heterostructure is simultaneously enhanced by the interlayer exciton resonances and by the hot carrier injection from the plasmonic metasurface. By optimizing the metasurface design, the responsivity can reach 1.35 A/W at 1550 nm, which is ~5 × 10⁴ times larger than that of a MoS₂/WSe₂ heterostructure on SiO₂/Si substrate. Furthermore, the broken mirror symmetry of the structure enables a chiral photoelectric response with discrimination ratios up to 7.2. Our study offers a promising platform for applications in NIR-Ⅱ bio-imaging, telecommunication, and on-chip spectroscopic sensing.