(a) Scanning electron microscope (SEM) image of the all-silicon metamaterial absorber. Inset: false color SEM view of the unit cell. (b) optically pumped terahertz probe spectrum of the all-silicon metamaterial absorber for different pump fluences. Inset: incident direction of the beams; the optical pump beam is at normal incidence and the THz probe beam is at 30° angle of incidence. (c) The peak absorption frequency, bandwidth, peak absorbance amplitude and absorbance at 0.5 THz. (d) experimental and simulation results (e) Simulation results with layered carrier density distribution to match the measured spectrum for different pump fluences in (b). Insets: the power loss density distribution for each resonant mode. (f) The theoretically calculated carrier density distribution along the z-axis in the all-silicon metamaterial absorber for different pump fluences. The bar plot represents the carrier density for each slice used in the simulation to match the spectrum for the maximum pump fluence [24].