Optically Tunable All-Dielectric Broadband Terahertz Metamaterial Perfect Absorber

We present a single-layer H-shaped all-silicon array exhibiting 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 upon the penetration depth of the pump beam in silicon, as demonstrated from simulation taking into account the depth dependence of the carrier concentration in the all-silicon metamaterial perfect absorber. The results unveil the tuning mechanisms in optically tunable all-silicon metamaterials and metasurfaces, guiding the development of functional all-dielectric functional terahertz devices, such as switches and modulators.