Imaging with a Terahertz quantum cascade laser

Abstract

We demonstrate bio-medical imaging using a Terahertz quantum cascade laser. This new optoelectronic source of coherent Terahertz radiation allows building a compact imaging system with a large dynamic range and high spatial resolution. We obtain images of a rat brain section at 3.4 THz. Distinct regions of brain tissue rich in fat, proteins, and fluid-filled cavities are resolved showing the high contrast of Terahertz radiation for biological tissue. These results suggest that continuous-wave Terahertz imaging with a carefully chosen wavelength can provide valuable data on samples of biological origin; these data appear complementary to those obtained from white-light images.

Nonlinear response of quantum cascade structures

“…Comparison with recent experimental data from time-domain-spectroscopy indicates that the experimental situation is beyond linear response. Possible coherent radiation in the terahertz range has been a very strong motivation for research in the field of terahertz quantum cascade lasers 1,2 (THz-QCLs), which would enable a wide range of applications such as imaging 3 and spectroscopy. 4 However, compact devices operating over cryogenic temperatures are a practical requirement for applications and currently the most promising designs are based on resonant phonon extraction, 5 achieving operating temperatures up to $200 K. 6 The key physical quantity in any QCL is the gain which describes the amplification of the optical field in the heterostructure material.…”

High-quality MBE growth of AlχGa1-χ As-based THz quantum cascade lasers

“…communications [1,2]. The production of THz waves by photonics or electronics have been tested using several approaches in this underdeveloped frequency range.…”

Temperature dependent nonlinear response of quantum cascade structures

“…Possible applications for sources in this frequency range are many, such as imaging [3] and spectroscopy [4]. In order to make these applications reality, compact and convenient systems operating over cryogenic temperatures are a necessity, and currently designs based on resonant phonon extraction [5] are the most promising.…”