Abstract
Electromagnetic radiation in the terahertz (THz) frequency band has
unique potential for future communication and imaging applications.
However, the adoption of THz technologies is hindered by the lack of
cost-effective THz sources. Here we demonstrate a way to generate and
control THz radiation, via spatio-temporal emissivity modulation. By
patterning the optical photoexcitation of a surface-passivated silicon
wafer, we locally control the free-electron density, and thereby
pattern the wafer’s emissivity in the THz part of the electromagnetic
spectrum. We show how this unconventional source of controllable THz
radiation enables a form of incoherent computational THz imaging. We
use it to image various concealed objects, demonstrating that this
scheme has the penetrating capability of other THz imaging approaches,
without the requirement of femtosecond pulsed laser sources.
Furthermore, the incoherent nature of thermal radiation also ensures
the obtained images are free of interference artifacts. Our
spatio-temporal emissivity control could enable a family of
long-wavelength structured illumination, imaging, and spectroscopy
systems.
Funder
Engineering and Physical Sciences
Research Council
European Research Council
Royal Academy of
Engineering
Subject
Atomic and Molecular Physics, and Optics,Electronic, Optical and Magnetic Materials