The interaction of light with resonant scattering centres is increasing in importance, for both fundamental research and technological applications, as experimentalists realise a growing number of such systems. Together with ready access to massive computer clusters, this has created the interesting confluence that we now have both the motive and the opportunity to study strong light coupling by means of microscopic numerical simulations. Advances in nanofabrication now allow us to reach high sensitivities with longer coherence times and an enhanced optical thickness (which characterises the light-matter coupling) in miniaturised devices. This results in a cooperative response and strong light-mediated interactions between the excitations of the scattering centres that poses a theoretical challenge in many-body physics with the eventual goal of reaching the quantum regime.
3D solid-state media as advanced resonance optical devices have encountered fundamental problems due to photon loss and fabrication challenges. These are being replaced by 2D metasurfaces, providing realisations of ultrathin, lightweight flat lenses with unprecedented functionalities.
In this project, the student will theoretically analyse and numerically simulate the collective responses of 2D arrays of subwavelength-spaced resonant scattering centres. Together with the research group they will develop methods for designing novel cooperative responses that can be utilised for optical manipulation and functionalities of ultrathin devices. By locally varying the properties of the system it is possible to build optical holograms and phenomena reminiscent of chirality that can be utilised for directed emission of light, as well as potentially for quantum devices, allowing the design of active optical media. The advantage of strong interactions is that the sensitivity of the optical devices is no longer limited by the resonance linewidth of the isolated scatterer, but by the collective resonance linewidth , which is potentially several times narrower. The project involves a close collaboration with experimental effort to build such structures in thin semiconductor layers of AlAs and GaAs  or MoSe , in photonic crystal and silicon arrays.
The student will join a theory group studying cooperative optical phenomena in different physical systems and will gain experience in large-scale numerical simulations and high-performance computing. The co-supervisor will be performing experiments on these systems, providing guidance on the suitability of the models for laboratory realisations.
Supervisor Prof. Janne Ruostekoski, Physics Dept, Lancaster, firstname.lastname@example.org
Co-supervisor Prof. Rob Young, Physics Dept, Lancaster, email@example.com
 S. D. Jenkins, J. Ruostekoski, N. Papasimakis, S. Savo, and N. I. Zheludev, Phys. Rev. Lett. 119, 053901 (2017).  G. Scuri et al., Phys. Rev. Lett. 120, 037402 (2018).  Patrick Back, Sina Zeytinoglu, Aroosa Ijaz, Martin Kroner, and Atac Imamoğlu, Phys. Rev. Lett. 120, 037401 (2018).