High-efficiency silicon THz modulator using optically injected carriers

A highly efficient and simply realizable method for broadband THz transmission modulation is demonstrated for pulsed THz TDS system using an optically switched B-doped silicon modulator. With 45 mW of absorbed 800 nm CW light, a maximum of 20.5 dB THz attenuation was achieved, with the technically important 3 dB loss reached at only 5 mW. These results show good agreement with the Drude-Lorentz model, whereby allowing the extraction of optically injected carrier damping rates, depicting a linear dependency of collision frequency on optically excited carrier density.