Dual-band terahertz biosensor based on metamaterial absorber

Traditional biological detection methods in practical applications, such as polymerase chain reaction, fluorescence microscopy, flow cytometry and so on, are commonly limited by label needed, high cost, complex operation, low sensitivity. Fortunately, metamaterial-based terahertz (THz) biosensors have shown great potential in label-free, integrated chip and ultra-sensitive sensing due to their advantages in light collection and miniaturization. However, most of THz metamaterial biosensors are based on transmission spectrum measurement, the one-way transmission will lead to the weak interactions between analyte and THz wave, so the sensitivity will be greatly reduced. Here, we proposed a label-free dual-band THz biosensor with ultra-high sensitivity based on metamaterial absorber. The device consists of the asymmetric cross shaped metal metasurface, hollow sensing channel and a back reflector. The simulation results show that the two resonance modes are excited at 0.626 THz and 1.504 THz and the absorptivity is higher than 95%. With the increasing the refractive index of the analyte, the two absorption peaks have obvious red shift. The maximum sensitivities for mode A and mode B are up to 250 GHz/RIU and 630 GHz/RIU, respectively. By simulating the electromagnetic field distribution of the structure, the absorption sensing mechanism is discussed in detail. The proposed THz metamaterial biosensor exhibits promising applications in chemical and biological detection.