Optically Modulated Ultra-Broadband All-Silicon Metamaterial Terahertz Absorbers

TLDR

Terahertz perfect absorbers are essential photonic components for detecting, modulating, and manipulating terahertz radiation. The study demonstrates tunable ultra‑broadband terahertz absorption using single‑layer H‑shaped all‑silicon arrays. The tunable response is governed by the pump‑beam penetration depth in silicon, modeled through simulations that account for depth‑dependent carrier concentration in the all‑silicon metamaterial. Experiment and simulation reveal near‑unity absorption at 1 THz with a ~913 GHz bandwidth for ≥90 % absorbance, a 420 GHz blueshift under optical tuning while maintaining >99 % peak absorbance, and CMOS compatibility enabling potential terahertz detectors and dynamic devices.

Abstract

Terahertz perfect absorbers represent an essential photonic component for detecting, modulating, and manipulating terahertz radiation. We utilize single-layer H-shaped all-silicon arrays to demonstrate tunable ultra-broadband terahertz wave absorption. Experiment and simulation reveal near unity absorption at 1 THz, with a bandwidth of ∼913 GHz for ≥90% absorbance. The absorption is optically tunable, exhibiting a resonance frequency blueshift by 420 GHz, while the peak absorbance remains over 99%. The dynamic response upon optical excitation depends on the penetration depth of the pump beam in silicon, as demonstrated through simulations that take into account the depth dependence of the carrier concentration in the all-silicon metamaterial perfect absorber. Notably, our all-silicon and ultrabroadband metamaterial perfect absorber is compatible with CMOS processing, potentially facilitating the development of terahertz detectors. Furthermore, the demonstrated tunable response may find potential applications toward creating dynamic functional terahertz devices, such as modulators and switches.