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Durham University

Research & business

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Dr Graham Cross, BSc., PhD., CPhys. MInst.Phys.

Senior Lecturer in the Department of Physics
Telephone: +44 (0) 191 33 43577
Room number: Ph323
Room number: 105

(email at


Teaching activity

Level 2 Laboratory Leader, L3 Team Projects

Research interests

I have a well established research history in the fields of light/matter interactions and development of optical waveguide photonic devices. Previous contributions have been to the area of nonlinear optical interactions in organic materials with the aim of finding materials and device solutions that would allow commercial application of polymers to photonics technologies.

My introduction of the biophysical characterisation method Dual Polarisation Interferometry (DPI) and its successful commercialisation is a highlight of my career to date.

The tool itself is now my focus of research into microscopic (linear) light/matter interactions. The current focus is on answering fundamental questions on the applicability of continuum models for the constitutive optical properties of matter when the evanescent light supplied by the DPI waveguide interacts with a highly dilute matter field.

Certain properties of materials such as the refractive index (or electrical conductivity) require energy transport models where the medium must be considered homogeneous on the relevant wavelength scales. But one could question the validity of effective medium models when permittivity discontinuities (e.g. 'refractive contrast' inclusions) are spaced beyond these scales. How can a conventional refractive index then be applied to explain the transport properties? In fact, to successfully use the concept of refractive index one has to assume that the incident electromagnetic field extends sufficiently across space to generate a notionally 'valid' statistical average of induced currents from all irradiated parts of the material. If this is not the case the refractive index loses its usual meaning and becomes irrelevant to the description of energy transport. One example of this reveals a fundamental limit to the use of continuum models of electromagnetism.

The DPI technique has the sensitivity and unique ability to record the quantitative and qualitative details of the phase paths taken by light propagating through such dilute discontinuous media. The experiments record data continuously during matter field (deposited layer) formation from dilute though to dense media and the complete phase path record reveals the matter field density point at which conventional homogeneous media assumptions can be safely applied. The technique has been dubbed a "Matter Field Microscope" where increasing the spatial frequency of the refractive discontinuities is akin to increasing the resolving power of a microscope. Light itself is the object of illumination in this inverted concept of microscopy.


Research Groups

Centre for Materials Physics

Department of Physics

Research Interests

  • Nonlinear optical materials
  • Optical waveguide devices
  • Optoelectronics

Indicators of Esteem

  • 2013: ERC reviewer: I continue to be an active member of the European Research Council's team of remote reviewers of research proposals.
  • 2008: IRCSET panel member:
  • 2007: Hosting FCO Visit From Korea: I was asked by the Foreign and Commonwealth Office in January 2007 to host a visit from the Director General of the Korea Science and Engineering Foundation, Hanjo Lim (similar to the Chief Executive of EPSRC) and a small party of senior Korean academics. Mr. Lim had identified my work on nanophotonics as typifying Durham's expertise in nanotechnology and I arranged for the party to visit a number of colleagues in Physics who also work on this topic.
  • 2007: IRCSET Panel Member: In April 2007 I was invited to join a panel assessing Fellowship Applicants to the Irish Research Council for Science, Engineering and Technology (IRCSET.) I joined the panel meeting in Dublin on 28th and 29th May to make the final decisions on likely successful applicants in the "Physics" category.
  • 2002: EPSRC College Membership: From 2002 until the present I have been a retained member of the EPSRC Peer Review College.


Media Contacts

Available for media contact about:

  • Physics: University start ups. I have been involved in starting up a successful company based on the research work I was doing and have an overview of the opportunities and pitfalls of this process.