Ultrafast optical techniques provide powerful probes of different states of matter, using light pulses that have femtosecond duration. In Warwick our activities span a number of areas:
studying the dynamics of the light-matter interaction in novel compounds and nanomaterials via terahertz spectroscopy and pump-probe methods,
performing terahertz medical imaging and spectroscopy,
developing methods and components for terahertz imaging and terahertz spectroscopy.
Group facilities
The Group has labs across the campus, in the main Physics building, Materials and Analytical Sciences, and Millburn House. Read more about our experimental capabilities in terahertz science and technology. We also run the Research Technology Platform.
We make use of a wide range of Warwick's excellent materials analysis equipment, including , Raman spectroscopy, and .
Join the group!
PhD positions are available for UK students and potentially for exceptional international students. Please get in touch if you are interested in PhD or MSc by Research topics in the group. We also support postdoctoral researchers to apply for independent fellowship schemes - let us know if that appeals.
Group, Theses & Photos
Contact details for our current and our photo gallery. For recent theses from the group, please see here.
Research areas
Nanomaterials
We use pump/probe spectroscopy to study how light and matter interact on femtosecond to nanosecond timescales. Using visible probes we can track electronic processes, while infrared radiation lets us study vibrational states of molecules and atomic-scale defects in semiconductors.
Performing in vivo studies of the THz properties of skin is a major initiative in the group, supported by the EPSRC Terabotics Programme GrantLink opens in a new window. We develop robust measurement protocols and test them on a statistically significant number of patients, cross-checking with other methods.
A major strand of our research is to improve our knowledge of the fundamental science underpinning new semiconductor materials, such as metal-halide perovskites, which are often attractive for photovoltaic applications.
We develop new THz devices and integrate them into novel systems designs that can perform THz imaging and THz spectroscopy faster, and with increased capabilities (e.g. polarisation control; robot-controlled probes).
T.J. Keat , D. J. L. Coxon, M. Staniforth, M. W. Dale, V. G. Stavros, M. E. Newton, and J. Lloyd-Hughes Phys. Rev. Lett. 129237401 (Nov 2022)
The perturbed free induction decay (PFID) observed in ultrafast infrared spectroscopy was used to unveil the rates at which different vibrational modes of the same atomic-scale defect can interact with their environment. The N3VH0 defect in diamond provided a model system, allowing a comparison of stretch and bend vibrational modes within different crystal lattice environments. The observed bend mode (first overtone) exhibited dephasing times T2=2.8(1) ps, while the fundamental stretch mode had surprisingly faster dynamics T2<1.7 ps driven by its more direct perturbation of the crystal lattice, with increased phonon coupling. Further, at high defect concentrations the stretch mode鈥檚 dephasing rate was enhanced. The ability to reliably measure T2 via PFID provides vital insights into how vibrational systems interact with their local environment.
J. Deveikis and J. Lloyd-Hughes Optics Express 3043293 (Nov 2022)
A multi-pixel photoconductive emitter is reported that generates THz beams with either azimuthal, radial or linear polarization states. Switching between the different polarization states was purely electrical, via the bias voltage applied, circumventing the need for mechanical polarization optics or different THz emitters to change the polarization. Dipole array modelling was performed to validate emitter array designs, and to explore their optimal bias configuration, while spatially-resolved electro-optic detection of the generated beams confirmed that cylindrical-vector beams were produced. We further demonstrate that the spatial beam profile was optimized by adjusting the bias level on particular pixels, improving the polarization purity of the beam.
X. Chen, H. Lindley-Hatcher, R. I. Stantchev, J. Wang, K. Li, A. I. Hernandez-Serrano, Z. D. Taylor, E. Castro-Camus and E. Pickwell-MacPherson Chem. Phys. Rev. 3, 011311 (June 2022)
Terahertz (THz) technology has experienced rapid development in the past two decades. Growing numbers of interdisciplinary applications are emerging, including materials science, physics, communications, and security as well as biomedicine. THz biophotonics involves studies applying THz photonic technology in biomedicine, which has attracted attention due to the unique features of THz waves, such as the high sensitivity to water, resonance with biomolecules, favorable spatial resolution, capacity to probe the water–biomolecule interactions, and nonionizing photon energy. Despite the great potential, THz biophotonics is still at an early stage of development. There is a lack of standards for instrumentation, measurement protocols, and data analysis, which makes it difficult to make comparisons among all the work published. In this article, we give a comprehensive review of the key findings that have underpinned research into biomedical applications of THz technology. In particular, we will focus on the advances made in general THz instrumentation and specific THz-based instruments for biomedical applications. We will also discuss the theories describing the interaction between THz light and biomedical samples. We aim to provide an overview of both basic biomedical research as well as pre-clinical and clinical applications under investigation. The paper aims to provide a clear picture of the achievements, challenges, and future perspectives of THz biophotonics.
X. Ding, A. I. Hernandez-Serrano, H. Lindley-Hatcher, R. I. Stantchev, J. Zhou and E. Pickwell-MacPherson Optics Express 30, 18079 (May 2022)
Terahertz time-domain spectroscopy (THz-TDS) has shown promise in biomedical sample characterization and high characterization sensitivity is in demand due to the thin-film (TF) feature of the sample. This paper proposes an optimized multilayer structure for sensitive characterization of TF aqueous solutions in reflection THz-TDS. Theoretical simulations are conducted for structural optimization and the 75 渭m window-sample-mirror structure displays the best sensitivity compared to other sandwich structures and traditional THz measurement geometries. 0-20% TF glucose solutions are then measured; and a spectral peak introduced by the proposed structure is observed to result in the high sensitivity. Our work provides a new way of customizing multilayer structure for THz thin-film characterization.
