The modern THz field arguably began with the development of a pulsed terahertz (THz) emitter – the semiconductor photoconductive switch – and the subsequent development of THz time-domain spectroscopy (TDS). Since then, considerable success has been achieved in the further development of this and other THz sources, including the uni-travelling carrier (UTC) photodiode and the quantum cascade laser (QCL). However, notwithstanding this, it is only the THz-TDS technology that has been developed sufficiently for commercialization as a complete system, leaving other THz devices, components and techniques still restricted to the academic laboratory. This is unfortunate, since despite the success of THz-TDS, the technique has some disadvantages including its high fs-laser dominated cost, low power, and limited frequency and spatial resolution, which could be addressed by QCL and UTC technologies if they were to be engineered into appropriate instruments.
In this programme, we will create the first comprehensive instrumentation for precise THz frequency spectroscopy, microscopy, and coherent control. This will be based upon our unique and proprietary capabilities to generate, and manipulate photonically, THz signals of unprecedentedly narrow (Hz) linewidth and with sub-wavelength spatial resolution. The instrumentation will then be exploited to create new challenge-led applications in non-destructive testing and spectroscopic analysis for electronics and atmospheric sensing, inter alia, as well as discovery-led opportunities within physics, quantum technologies, materials science, atmospheric chemistry and astronomy. The new instruments will have wide-ranging application for both industrial and academic end-users.
Working with our project partners, our objectives are to:
- develop robust, frequency-locked THz spectrometers, operating between 100 GHz–5.5 THz with a <30 Hz target linewidth and frequency accuracy <1 Hz, referenced to primary frequency standards, in compact and portable instruments, suitable for easy transport between partner sites and to end-users;
- develop room temperature and cryogenic near-field scanning THz microscopes, exploiting both scattering- and aperture- approaches, providing coherent spectroscopy with ultimately sub-10-nm spatial resolution, and up to 10-100 µm/s scanning speeds;
- integrate our technology into a commercial AFM/SNOM platform with NeaSpec, develop low-temperature capability with Lake Shore, and prove instrument viability with TeraView on site in their R&D facilities and applied to samples of industrial relevance in the electronics sector;
- develop high power bench-top QCL-based instruments capable of producing synchronized intense, narrowband, transform-limited pulses from ~2–5 THz, with pulse lengths <10 ps–10 ns, and electrically controlled arbitrary pulse sequences with pulse separations to <50 ps;
- develop new understanding of quantum confined systems including entangled single-photon sources with Toshiba, rare earth ion-in-solid materials and Rydberg impurity systems with the EPSRC Quantum Technology Hub in sensors and metrology, and high frequency manipulation of quantum dots and wires, e.g. supporting the current standard communities including NPL;
- deliver precision THz heterodyne sounders for analysis of key species including O and OH at 4.7 THz and 3.5 THz, respectively, on aircraft with DLR in Germany, and satellite missions with RAL, for which there is no current technological solution;
- develop a toolkit of components to couple THz radiation into difficult to access environments.