Active optical control of the terahertz reflectivity of high-resistivity semiconductors

We study theoretically and demonstrate experimentally light-controllable terahertz reflectivity of highresistivity semiconductor wafers. Photocarriers created by interband light absorption form a thin conducting layer at the semiconductor surface, which allows the terahertz reflectivity of the element to be tuned between antireflective (R < 3 %) and highly reflective (R > 85 %) limits by means of the intensity and wavelength of the optical illumination. (c) 2005 Optical Society of America.