High‐Performance Photo‐Induced Spatial Terahertz Modulator Based on Micropyramid Silicon Array

Abstract Reconfigurable conductive pattern created by photoexcitation of high‐resistivity semiconductor provides a powerful approach to realize broadband spatial terahertz modulators (STM), which are highly demanded for constructing cost‐effective and compact terahertz (THz) system. Here a high performance all‐optical STM is proposed and realized based on silicon micropyramid arrays (Si‐MPA), which not only enhances the light harvesting across a broad wavelength range, but also greatly increases the active area for THz modulation. Upon illuminating the Si‐MPA by light with various wavelengths, modulation depth (MD) of four times larger than that of bare silicon is achieved. A maximum MD of 93.8% is obtained under 638 nm laser with a low power density of 1 W cm −2 . Reconfigurable THz imaging system based on the Si‐MPA modulator and a single‐element detector is constructed, with which precise THz beam mapping and fast real‐time imaging with 225 pixels are demonstrated. This Si‐MPA‐based STM with large MD at low illumination power density is promising for many THz applications including imaging, beam shaping, holographic projection, etc.