Terahertz imaging through emissivity control

TL;DR

This paper introduces a novel, cost-effective method for generating and controlling terahertz radiation through spatio-temporal emissivity modulation, enabling advanced imaging without expensive pulsed lasers.

Contribution

It presents a new approach to produce controllable THz radiation by patterning optical excitation on silicon, facilitating incoherent computational THz imaging with improved capabilities.

Findings

Successfully imaged concealed objects using the new THz source

Demonstrated penetration depth comparable to state-of-the-art methods

Images are free of interference artifacts due to thermal emission nature

Abstract

Adoption of terahertz technologies is hindered by the lack of cost-effective THz sources. Here we demonstrate a fundamentally new 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 new form of incoherent computational THz imaging. We use it to image various concealed objects, demonstrating this scheme has the penetrating capability of state-of-the-art THz imaging approaches, without the requirement of femto-second 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 paves the way towards a new family of long-wavelength structured illumination, imaging and spectroscopy systems.