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Figure 3: Optically tuned THz modulator based on semiconductor materials and metamaterials. Panel . (a) SEM images of the fabricated InSb grating. (b) Normalized THz signals as a function of delay time measured by OPTP under different pump laser fluences and the exponential curve fittings. Reproduced from [42]. Panel . (a) Schematic view of THz wave transmission measurement for bilayer samples. (b) Dielectric functions obtained from pentacene/Si thermally annealed at various temperatures. Reproduced from [43]. Panel . (a) Prototype and spatial configuration of the Si-nanotip-based spatial THz modulator. (b) THz transmission amplitude (left) and the modulation depth (right) of different modulators as a function of the laser pumping power. Reproduced from [44].