High-Q guided mode resonances in terahertz all-silicon metasurfaces

Abstract We proposed and experimentally demonstrate the realization of high-Q guided mode resonances (GMRs) in an all-silicon terahertz (THz) metasurface. The metasurface consists of an array of rectangular air slots within a silicon wafer. Multiple low-order TE and TM GMRs in the frequency range of 0.40–0.75 THz are considered in the investigation. The results show that the Q-factors of the GMRs can be easily tuned at very large range by varying the length of the slots, and increase remarkably when the length approaches the period of metasurface. The metasurfaces were prepared using the deep reactive ion etching (DRIE) technique, and subsequently measured using a THz frequency-domain spectroscopy system that features high spectral resolution. The experimental results are in good agreement with the simulations, and the largest measured Q factor of GMRs reaches up to 591. The proposed all-silicon metasurface with high Q-factor is ease of fabrication and has great potential for application in THz sensing, filtering and modulation.