He-Ne laser and speckle
He-Ne laser and speckle
Gibbous moon
Gibbous moon
Water droplet
Water droplet
Electron tree
Fractal electron tree or Lichtenberg figure
Oscilloscope trace
Oscilloscope trace
Soap bubble colour fringes
Soap bubble colour fringes

About us

We are a theoretical research group forming part of the Photonics Division located at the Blackett Laboratory of Imperial College London. The group is lead by Dr. Matthew R. Foreman who currently holds a Royal Society University Research Fellowship.

Our research focuses on optical and plasmonic sensing, polarisation sensitive imaging, disordered media and electromagnetic theory. More information on some of our past and present projects can be found by visiting our Research pages.

Recent news

IOP Stochastic Electromagnetism and Coherence Conference

6 Sep 2021: Matthew gave a keynote talk as part of the IOP Stochastic Electromagnetism and Coherence Conference discussing our recent work on modelling of polarisation imaging through scattering media. There was a wide diverse range of speakers at this interesting event. Many thanks to the organisers for the invitation.

Absorption and multiple scattering enhanced particle sensing - paper published

2 Aug 2021: The second of our papers discussing enhancing single particle detection using multiple scattering has just been published in Physical Review Research. This article focuses on the particular role absorption can play on achievable enhancements.

OSA Optical Sensors and Sensing Congress

21 Jul 2021: Joel will be presenting his recent work on tracking single particles using random scattering at the OSA Optical Sensors and Sensing Congress tomorrow as part of the Nanophotonics and Plasmonics Biosensors III session. If you are attending then check out his talk!

Recent publications

N. Byrnes and M. R. Foreman, "Polarisation statistics of vector scattering matrices from the circular orthogonal ensemble" Opt. Commun. in press (2006).

Abstract : We study the polarisation properties of random N × N scattering matrices distributed according to the circular orthogonal ensemble. We interpret 2 × 2 sub-blocks of the scattering matrix as Jones matrices and study their statistical properties. Using the polar decomposition, we derive probability density functions for retardance and diattenuation from scattering matrices of arbitrary size and in the limit N → ∞.

J. Berk and M. R. Foreman, "Role of Multiple Scattering in Single Particle Perturbations in Absorbing Random Media" Phys. Rev. Research 3, 033111 (2006).

Abstract : Speckle patterns produced by disordered scattering systems exhibit a sensitivity to addition of individual particles which can be used for sensing applications. Using a coupled dipole model we investigate how multiple scattering can enhance field perturbations arising in such random scattering based sensors. Three distinct families of multiple scattering paths are shown to contribute and the corresponding complex enhancement factors derived. Probability distributions of individual enhancement factors over the complex plane are characterised numerically within the context of surface plasmon polariton scattering in which absorption is shown to play an important role. We show that enhancements become more strongly dependent on individual scatterer properties when absorption losses are larger, however, amplitude enhancements ~10^2, comparable to low loss surface plasmons, are achievable through sensor optimisation. Approximate analytic expressions for the complex mean enhancements are also found, which agree well with simulations when loop contributions are negligible.

J. Berk and M. R. Foreman, "Theory of Multiple Scattering Enhanced Single Particle Plasmonic Sensing" ACS Photon. 8, 2227-2233 (2006).

Abstract : Methods to increase the light scattered from small particles can help improve the sensitivity of many sensing techniques. Here, we investigate the role multiple scattering plays in perturbing the scattered signal when a particle is added to a random scattering environment. Three enhancement factors, parametrising the effect of different classes of multiple scattering trajectories on the field perturbation, are introduced and their mean amplitudes explored numerically in the context of surface plasmon polariton scattering. We demonstrate that there exists an optimum scatterer density at which the sensitivity enhancement is maximised, with factors on the order of 10^2 achievable. Dependence of the enhancement factors on scatterer properties are also studied.

Funding

Our research is supported by generous funding from:

EPSRC
The Royal Society
Microsoft Research