Giant Broadband Electric Field Enhancement Mediated by Ω–Shaped Antenna and Its Application on Ultrasensitive Terahertz Detectors

ABSTRACT Receiving antennas that concentrate the free–space electromagnetic energy into the deep sub–wavelength feed gaps can significantly improve the performance of terahertz (THz) detectors. However, narrow bandwidths of traditional resonant antennas limit the response bandwidth of THz detectors. Here, we propose Ω–shaped split ring (OSR) antennas and demonstrate their application in THz detectors. First, the inductive–capacitive and the fundamental dipole resonances of OSR antennas are systematically investigated. Owing to the shrinkage of frequency interval and the resultant synergistic effects between the two resonant modes, the OSR antenna demonstrates a high designed electric field enhancement factor of larger than 40 within a wide bandwidth of 0.4 THz. Subsequently, we design and realize an asymmetrically OSR–antenna–integrated THz photothermoelectric (PTE) graphene detector on a flexible polyimide substrate. The OSR–antenna–induced giant THz electric field enhancement greatly improves THz free–carrier absorption in the graphene channel and drives a fast and sensitive PTE response. In room temperature and zero–bias working conditions, the flexible THz detector demonstrates an excellent detection performance with a fast response (8 µs), a high responsivity (908 V/W), and a high sensitivity (5.8 pW/Hz 1/2 ). Our research shows that the OSR antennas have great potential to realize high–performance flexible THz sensing devices.