Professor John Cunningham

Professor John Cunningham

Responsibilities

  • Deputy Head of School
  • Director of Teranet

Research interests

My work chiefly concerns the development of high frequency (megahertz to terahertz) electronic and photonic techniques for the interrogation and manipulation of a wide range of systems, with particular emphasis on semiconductor nanostructures.

A major theme of my work has been the development of on-chip terahertz systems, which provide a versatile way to confine THz radiation to length-scales far below the diffraction limit of freely propagating THz radiation.  In these systems, pulses of THz radiation are generated using an ultrafast laser, and are then guided through lithographically defined waveguides, where they interact with either samples or devices, before being detected.  We have used this technique to develop many spectroscopy, imaging, and sensing applications.  Since the size of these systems is limited only by lithographic considerations, they are ideally suited to study the THz response of individual mesoscopic systems and nanostructures.  

A second theme of my work is the development of new applications for high frequency (MHz to 10's GHz) surface acoustic waves (SAWs).  SAW filters find commercial application as delay lines in mobile phones, but we use SAWs as a way to provide a high frequency perturbations to micro- and nano-structures.  The piezoelectric potential which accompanies the mechanical movement of a SAW can be used to push charge through semiconducting materials - the so-called acoustoelectric transport.  We demonstrated this effect in graphene for the first time. We have also demonstrated the meschanical alignment and transport of micron scale particles in microfluidic systems mediated by SAWs.

Another, more recent application for high frequency acoustic waves has been our demonstration of modulation of the light output of terahertz quantum cascade lasers.   THz QCLs offer the potential for high data rate communications in both terrestrial and satellite communications, with the picosecond relaxation times in principle enabling modulation rates exceeding 100 GHz.  However, in practice, electrical modulation frequencies are usually limited to 10s of GHz, owing to parasitic inductance/resistance of the circuits in which they are embedded.  We recently showed that acoustic waves could be used to overcome these limits.  The results were published in Nature Communications in early 2020 and went to be widely reported internationally (see https://tinyurl.com/rltx6lm).

Much of the above work makes use of our School’s extensive cleanroom fabrication facilities, which include electron beam lithography, while experiments are undertaken in our world-class THz photonics laboratory.  Our facilities include Ti:sapphire lasers, and a range of cryostats, including the world’s first 12T, 8mK base temperature cryogen-free dilution refrigerator.  

I am always interested in hearing from potential collaborators and PhD students.  If you have ideas for new collaborative projects, or would like to discuss potential PhD topics in related areas, please send me an email.

Research groups and institutes

  • Pollard Institute
<h4>Postgraduate research opportunities</h4> <p>We welcome enquiries from motivated and qualified applicants from all around the world who are interested in PhD study. Our <a href="https://phd.leeds.ac.uk">research opportunities</a> allow you to search for projects and scholarships.</p>