Digital imaging through terahertz multifrequency programmable metasurface based on BIC

Abstract

Due to its intense penetration and low photon energy, terahertz (THz) imaging has been widely applied in biomedical imaging, non-destructive testing, and digital holography. The traditional method of exciting THz is through plasmon polariton coupling, which faces low photon signal excitation sustainability and poor polarization coupling efficiency challenges. This paper proposes a multi-channel THz system based on a high Q-factor bound state in the continuum (BIC) cross-polarization. The system is composed of an Al-graphene programmable metasurface. As an application of this programmable metasurface, we manage a field-programmable gate array (FPGA) to independently adjust the transmission properties of sub-arrays by changing the graphene state on the programmable metasurface through computer control. This feature enables our metasurface, which dynamically display characters in multiple channels, and provide a platform for THz multi-band image encryption and transmission. Additionally, we offer a convenient and stable method to generate multi-frequency effects by coupling bright modes that can produce BIC effects with dark modes that are not excited in that polarization state. Compared with traditional excitation methods, this method is more accessible to process due to its simple device structure.