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A Janus layered metamaterial (JLM) operating in the terahertz (THz) region is proposed, which increases the direction dimension to manipulate the propagation of electromagnetic waves (EWs) through the introduction of nonlinear Kerr media. It achieves multi-scale multitasking with different logic gates and mode-switching biosensing, making a breakthrough on traditional single-function and single-scale THz devices. Due to the electro-optical effect, the liquid crystal (LC) is adjusted by the electric field, and the sharp transmission peak generated by the located defect mode resonance can be used to realize the forward scale logic product gate and the backward scale exclusive NOR gate. In addition, by locking the sharp transmission peak, the biosensing can have different detection ranges under the LC modulation. Therefore, when EWs propagate forward and backward, the mode switching of different biosensing categories with a glucose concentration of 300–550 g/l, creatinine concentration of 80.9–85.28 μmol/l, and the blood component in refractive index of 1.33–1.38 can be realized. The JLM proposed provides a possibility for the design of the chip-level compact optical integrated circuit and offers a new idea for multi-purpose biomedical detection, owning certain research value. [ABSTRACT FROM AUTHOR]

Photonic spin Hall effect (PSHE) is an effective metrological tool to characterize the variation in weak refractive index (RI) and nanostructure parameters. In this Letter, a highly sensitive terahertz Janus sensor (JS) based on PSHE is proposed. Through the asymmetric arrangement of different dielectrics, the sensor has a Janus feature, realizing the multitasking of thickness and RI detection on multiple scales. When electromagnetic waves (EWs) are incident into the JS from the forward scale, the number of graphene layers (1–7 layers) can be exactly identified by thickness detection. Enhancing the PSHE by the property of graphene, the JS can extend the thickness change of the graphene layer at the nanometer level by 106 times to the millimeter level with a sensitivity of 3.02 × 10−3 m/nm. In the case of EWs backward scale propagation, based on the sensitivity of 6.244 × 10−3 m/RIU, the JS can identify different kinds of waterborne bacterium such as Vibrio cholerae, Escherichia coli, and Shigella flexneri, in the RI range of 1.355–1.43 with high precision. The design of the multiscale and multitasking JS with high sensitivity is of great significance for accelerating the research and exploration of graphene materials. In addition, it provides an idea for real-time, no-label, and low-cost detection in the biomedical field. [ABSTRACT FROM AUTHOR]