The early programme, which ran from years 1 – 3, was comprised of three interrelated projects, with a technological core comprising the development of high-precision spectroscopy (Project 1), coherent source control (Project 1), and near-field microscopy techniques and instrumentation (Project 2), directed towards application-driven instrumentation (Project 3).
Project 1: High-Precision THz Spectrometers was aimed at developing four instruments: a tuneable optical comb source operating up to 5 THz, with a target linewidth <30 Hz and frequency accuracy referenced to primary frequency standards; a UTC-based spectrometer for frequencies up to 3 THz and a QCL-based spectrometer for frequencies up to 5 THz, and including multimode phase control, both with a target linewidth <30 Hz, frequency resolution <1 Hz determined by the microwave reference resolution and frequency accuracy referenced to primary frequency standards, in compact and portable instruments; and, a high-power THz QCL spectrometer (>100 mW, ~2–5 THz) delivering transform-limited pulses from 10 ps to >1 ns, and electrically controlled arbitrary pulse sequences.
“The development of high precision spectrometers, and intense pulsed QCL-based sources, will enable new understanding and manipulation of quantum-confined systems that collectively have relevance to future quantum information processing, optical fibre amplifiers, new laser gain media, photon-assisted tunnelling, single-photon sources, and in fundamental physics and chemistry studies of nonlinear phenomena, coherent control and non- equilibrium systems.”
Project 2: Coherent Terahertz Microscopes explored: the first THz scattering-type scanning near-field optical microscope (THz-s-SNOM), providing 10 nm spatial resolution, based on antenna-enhanced scattering probes and exploiting coherent self-mixing detection; the first THz-s-SNOM operating at cryogenic temperatures, providing sub-30-nm spatial resolution at kHz scanning rates, exploiting a tuning fork probe and fast detection schemes; and, the first THz aperture-type scanning near-field optical microscope (THz-a-SNOM) exploiting probes with embedded nanoscale detectors operating at room and cryogenic temperatures, enabling high-resolution (<1 μm) microscopy and coherent spectroscopy, with 10–100 μm/s scanning speeds for large-area (~mm) imaging.
“Our robust frequency-locked QCL spectroscopy systems will find applications as local oscillators in satellite instrumentation for Earth-observation and planetary science, and in high-precision gas spectroscopy, and will be of interest to chemists, atmospheric chemists, astronomers, and electronic engineers.”
Project 3: Translation and Applications applied and developed the Project 1 and Project 2 technology in proof-of-concept studies. For example, we developed new understanding of quantum confined systems at mK temperatures including: rare earth ion-in-solid materials, of importance for optical fibre amplifiers, new laser gain media, and quantum information applications; isolated impurities in semiconductors demonstrating coherent manipulation of electronic states; and, one- and zero-dimensional semiconductor systems, formed by electrostatic confinement, etching, and self-organized growth. The manipulation and control of self-assembled InAs dots will lead to quantum information applications. We developed robust THz spectroscopy systems, exploiting frequency-locked QCLs as local oscillators in compact mixer blocks for use in satellite instrumentation for Earth-observation and planetary science, of importance for understanding, e.g., climate change processes. We also built on our THz waveguide technology and develop a toolkit of components to couple radiation into cryostats and other difficult-to-access environments.
“Our development of room temperature and cryogenic microscopes, with ultimately sub-10-nm spatial resolution, will allow the sub-wavelength probing of condensed matter systems, relevant to material scientists and condensed matter physicists.”
