The Terahertz Physics Group at the University of Manchester is led by Dr Darren Graham and is focused primarily on the exploitation of ultrafast laser-based terahertz radiation sources and terahertz time-domain spectroscopy. We address challenges both within the fields of photon physics and accelerator physics. Within the field of photon physics, we use terahertz spectroscopy to probe the fundamental properties of materials being developed for the next generation of photonic and electronic devices. Our work within the field of accelerator physics is focused on using sub-picosecond terahertz radiation pulses to manipulate electron beams and ultimately shrink the size of particle accelerators. This work involves utilising the state-of-the-art laser facilities at the Photon Science Institute (PSI) and the accelerator facilities at STFC Daresbury Laboratory.

 

 

Latest News

 

Two presentations were given at the 43rd International Conference IRMMW-THz in Nagoya, Japan in September. Morgan Hibberd gave a talk on “Magnetic-field patterning of a spintronic source for arbitrary terahertz polarization control” and Darren Graham a keynote talk on “Developing a terahertz-driven dielectric-lined waveguide for electron beam manipulation”, which described recent work in collaboration with the Cockcroft Institute.

PhD student Vasileios Georgiadis also recently gave a talk his work on “Characterizing a dielectric-lined waveguide” at the Photon 2018 conference, Aston University.

Other News

Demonstration of Slow Light Published in Nature Communications – Sept. 2017
Asylum seeker becomes a PhD student in the group – July 2016
Researchers create innovative instrument - May 2016
Springer Thesis Prize Awarded to Matthew Cliffe - March 2016
RS grant awarded to Darren Graham - March 2016
Terahertz driven particle accelerators - Feb. 2016
New Grant – Breaking the frequency barrier - 2015
Longitudinally polarized terahertz pulses: paper by Matthew Cliffe  - Nov. 2014
Importance of good alignment in THz systems: paper by Matthew Cliffe – June 2014

 

 

 

PhD Projects

The PhD project descriptions listed below are provided to give applicants a flavour of what research study is available. For further information contact Darren Graham.

·         Terahertz driven linac: Shrinking the size and cost of particle accelerators

·         Gallium Nitride: A miracle material for exploiting the full spectrum of light

·         Terahertz spintronics: Enabling the exploitation of electron spin

Group Members

Group Leader
Darren Graham, MPhys (Hons), Ph.D., MInstP 
Lecturer in Physics
School of Physics and Astronomy, The University of Manchester
E-mail: Darren.Graham@manchester.ac.uk
Google Scholar - https://scholar.google.co.uk/citations?user=SO6OV-cAAAAJ&hl=en
The University of Manchester staff profile

Morgan Hibberd, MPhys (Hons), Ph.D.
Post-doctoral Research Associate
School of Physics and Astronomy, The University of Manchester
E-mail: Morgan.Hibberd@manchester.ac.uk

PhD Students

Image result for Abbas Roble MAnchester

Daniel Lake

Adam Shorrock

Abbas Roble

Vasileios Georgiadis

 

Selected Publications

 

Magnetic-field tailoring of the terahertz polarization emitted from a spintronic source
Hibberd, M. T., Lake, D. S., Johansson, N. A. B., Thomson, T., Jamison, S. P.,  and Graham, D. M.,
Applied Physics Letters 114, 031101 (2019), DOI: 10.1063/1.5055736

We demonstrate a method to create arbitrary terahertz (THz) polarization profiles by exploiting the magnetic field-dependent emission process of a spintronic source. As a proof-of-concept, we show that by applying a specific magnetic field pattern to the source, it is possible to generate a quadrupole-like THz polarization profile. This unique ability to generate any desired THz polarization profile opens up possibilities for schemes such as rotatable polarization spectroscopy and for efficient mode coupling in various waveguide designs.

 

 

Demonstration of sub-luminal propagation of single-cycle terahertz pulses for particle acceleration,
Walsh, D. A., Lake, D. S., Snedden, E. W., Cliffe, M. J., Graham, D. M. & Jamison, S. P.,
Nature Communications. 8, 421 (2017),
DOI: 10.1038/s41467-017-00490-y

We describe and demonstrate a method for generating single-cycle terahertz pulses that propagate with an effective sub-luminal phase velocity, and without distortion during propagation.  This novel travelling source approach fulfils the requirement for a sub-luminal phase velocity in laser-driven particle acceleration schemes without the need for dispersive structures or waveguides to extend the field-particle interaction.

 

 

Dielectric response of wurtzite gallium nitride in the terahertz frequency range, Hibberd, M., Frey, V., Spencer, B., Mitchell, P., Dawson, P., Kappers, M. J., Oliver, R. A., Humphreys, C. J. & Graham, D. M., Solid State Communications. 247, 68-71 (2016), DOI: 10.1016/j.ssc.2016.08.017

In this work the intrinsic, anisotropic, dielectric properties of wurtzite gallium nitride in the spectral range of 0.511 THz are determined from a semi-insulating m-plane gallium nitride single crystal, providing measurements of the refractive indices and absorption coefficients. These results will provide the essential material parameters to assist in the future design of terahertz devices based on wurtzite GaN.

 

 

 

Terahertz cyclotron resonance spectroscopy of an AlGaN/GaN heterostructure using a high-field pulsed magnet and an asynchronous optical sampling technique, Spencer, B. F., Smith, W. F., Hibberd, M. T., Dawson, P., Beck, M., Bartels, A., Guiney, I., Humphreys, C. J. & Graham, D. M., Applied Physics Letters. 108, 212101 (2016),
DOI: 10.1063/1.4948582

We have shown that by modifying an asynchronous optical sampling detection scheme THz cyclotron resonance spectroscopy may be performed with a high-field pulsed magnet in a laboratory environment. The development of this instrument has allowed us to determine the fundamental properties of a two-dimensional electron gas in an AlGaN/GaN heterostructure.

 

 

 

Longitudinally polarized single-cycle terahertz pulses generated with high electric field strengths, Cliffe, M. J., Graham, D. M. & Jamison, S. P., Applied Physics Letters. 108, 221102 (2016), DOI: 10.1063/1.4953024

By using a matched pair of polarity inverted MgO:SLN crystals as an optical rectification source, we demonstrate the generation of strong on-axis longitudinally polarized single-cycle terahertz radiation, with electric field amplitudes in excess of 11 kV/cm. In contrast to segmented waveplate sources, the single-cycle terahertz temporal profile is maintained hence maximizing the attainable electric field strength.

 

 

Generation of longitudinally polarized terahertz pulses with field amplitudes exceeding 2 kV/cm, Cliffe, M. J., Rodak, A., Graham, D. M. & Jamison, S. P., Applied Physics Letters. 105, 191112 (2014), DOI: 10.1063/1.4901904

We demonstrate the generation of near-single cycle longitudinally polarized terahertz radiation using a large-area radially biased photoconductive antenna with a longitudinal field amplitude in excess of 2 kV/cm. The 76 mm diameter antenna was biased with a voltage of up to 100 kV applied over concentric electrodes. By tightly focusing the radiation emitted from the antenna, we obtained a longitudinal field amplitude of 2.22 kV/cm.