Broadband near infrared all-dielectric metasurface absorber

•The absorber with asymmetric nanohole arrays gives rise to a broadband absorption.•Its all-dielectric structure is compatible with the standard CMOS techniques.•The design is suitable for the photodetectors from intraband & interband transitions.•Moreover, the underlying physical mechanisms are duly discussed. Here we present a broadband all-dielectric metasurface absorber, where elliptical nanohole arrays are entirely embedded into the doped device layer of silicon-on-insulator wafer. From the intraband carrier transitions, the device exhibits enhanced near infrared absorption with a 3-dB bandwidth ∼ 35.3 nm. By the method of detailed multipole decomposition, we find that magnetic dipole resonances predominantly contribute to the absorption enhancement; in addition, the large bandwidth is attributed to the superposition of multiple absorption peaks from the resonances. The absorber designed in this simple structure and compatible with the CMOS techniques is promising for the broadband photodetectors of Si and even Ge. Differently, for the Ge-based photodetectors, the photocarrier excitation originates from interband transitions.