Passive THz Imager
Project Supervisors: Dr V Antonov
Terahertz radiation (also far infrared or submillimeter radiation) is naturally
emitted by all objects. It occupies frequency range from 0.1- to 5 THz. The
radiation emitted contains all information about constituency and internal
structure of the objects. As a result the terahertz range has potential
applications in many fields like Biochemical Analysis, Security Screening,
Biological Health Screening and Space/Earth observation. Operation in this
wavelength range has a number of advantages: (i) an imager can be a passive
device capturing pictures of the radiation naturally emitted, (ii) terahertz
rays can pass easily through many solid materials, (iii) the radiation can be
focused like light to create images of objects. Astrophysics already benefited
from studying Terahertz spectrum emitted by the cold objects/clouds in space. In
medicine the terahertz systems showed usefulness for early diag
nostics
of the diseases in live cells. However all advantages of the terahertz radiation
can be exploited only with a sensor of high sensitivity having a Noise
Equivalent Power (NEP) less than ~10-19
.
Modern detectors have an NEP two orders of magnitude larger. The photons
in this region are difficult to handle on an individual basis because a typical
photon energies are as small as a few meV. Therefore only a substantial flux of
photons can be detected by traditional devices. We design and study a new
Passive Terahertz imager,
which is sensitive enough to detect naturally emitted radiation. It
consists of a high sensitive Quantum Dot detector with an NEP better than
~10-19,
an advanced calibration source, and an optical system delivering radiation
emitted by the objects from room temperature to the detector kept in
refrigerator at 1K. On the way to the detector a high frequency radiation is
filtered and, if necessary, band pass filters rectify important spectral lines.
The radiation is then probed by the QD detector. Thus the terahertz image of the
object is taken. An outline of the research is as follows: the development and
optimisation of the QD detector; the development of the optical system and the
calibration source; imaging of the objects held at room temperature and analysis
of these images. The research would be undertaken in the Department of Physics,
Royal Holloway, University of London, where extensive facilities and
infrastructure for low temperature physics and nanotechnology already exist.
This multifaceted and challenging project involves collaboration of the
Nanophysics Group at Royal Holloway, National Physical Laboratory and Tokyo
University.
On-line application form for PhD programme can be loaded from university
website.