Terahertz chiral metasurface based on Cu-decorated laser-induced graphene

Terahertz (THz) chiral metasurfaces are crucial for advanced applications in biochemical sensing and communications. Nevertheless, the performance of multi-layered metallic metasurfaces is restricted by their limited chirality and challenges in alignment. This work reports a high-performance bilayer chiral metasurface based on copper-decorated laser-induced graphene (Cu-decorated LIG). By incorporating anhydrous copper chloride CuCl₂ into the polyimide precursor, the conductivity and electromagnetic loss of the decorated LIG is significantly enhanced. To construct the multilayer architecture, a novel mask-free and transparency-independent alignment strategy was developed, utilizing UV-curable adhesive as a bonding medium. This approach successfully overcomes the alignment bottleneck associated with opaque flexible substrates in traditional photolithography. The geometric design consists of an “S”-shaped unit cell comprising two “C” rings with a 180°opening angle. Experimental results demonstrate that the LIG/Cu-0.4 configuration achieves a giant CD of 98% at 0.95 THz. Furthermore, the developed metasurface was successfully employed for the high-sensitivity sensing of lactose. This study provides a facile, low-cost, and universal approach for constructing high-performance multilayer THz chiroptical platforms, offering broad potential for label-free biochemical detection.