Photomechanical meta-molecule array for real-time terahertz imaging

Real-time terahertz (THz) imaging offers remarkable application possibilities, especially in the security and medical fields. However, most THz detectors work with scanners, and a long image acquisition time is required. Some thermal detectors can achieve real-time imaging by using a focal plane array but have the drawbacks of low sensitivity due to a lack of suitable absorbing materials. In this study, we propose a novel photomechanical meta-molecule array by conveniently assembling THz meta-atom absorbers and bi-material cantilevers together, which can couple THz radiation to a mechanical deflection of the meta-molecules with high efficiency. By optically reading out the mechanical deflections of all of the meta-molecules simultaneously, real-time THz imaging can be achieved. A polyimide sacrificial layer technique was developed to fabricate the device on a glass wafer, which facilitates the transmission of a readout light while the THz wave radiates onto the meta-molecule array directly from the front side. THz images and video of various objects as well as infrared images of the human body were captured successfully with the fabricated meta-molecule array. The proposed photomechanical device holds promise in applications in single and broadband THz as well as infrared imaging.