Abstract
We report a coherent terahertz (THz) imaging system that utilises a quantum cascade laser (QCL) operating in pulsed-mode as both the source and detector. The realisation of a short-pulsed THz QCL feedback interferometer permits both high peak powers and improved thermal efficiency, which enables the cryogen-free operation of the system. In this work, we demonstrated pulsed-mode swept-frequency laser feedback interferometry experimentally. Our interferometric detection scheme not only permits the simultaneous creation of both amplitude and phase images, but inherently suppresses unwanted background radiation. We demonstrate that the proposed system utilising microsecond pulses has the potential to achieve 0.25 mega-pixel per second acquisition rates, paving the pathway to video frame rate THz imaging.
Highlights
Terahertz (THz) frequency (∼ 0.1–10 THz) radiation is attractive for a diverse range of imaging and sensing applications due to the unique properties of THz waves
In this article we demonstrate a pulsed-mode Laser feedback interferometry (LFI) imaging system built around a THz quantum cascade laser (QCL) operating as a homodyning transceiver in a compact mechanical cryogen-free Stirling cooler
We have demonstrated the feasibility of a high-speed pulsed-mode LFI imaging system based on a THz QCL operating as a single pixel coherent detector — a necessary prerequisite for video frame rate image formation
Summary
Terahertz (THz) frequency (∼ 0.1–10 THz) radiation is attractive for a diverse range of imaging and sensing applications due to the unique properties of THz waves. Using a THz QCL as an illumination source allows for higher resolution imaging than sub-THz systems (due to the shorter wavelength) and many orders of magnitude more power (> 100 mW) than typical time-domain systems [26]. The most direct approach is to use an external single-pixel detector in a scanning configuration (see [21] and references therein) Such systems require relatively complicated optical setup and careful alignment of the QCL source and the detector
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