He-Ne laser and speckle
He-Ne laser and speckle
Electron tree
Fractal electron tree or Lichtenberg figure
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

Congratulations Joel!

17 Dec 2021: Well done to Joel for submitting his PhD thesis today! With all the turbulence of the pandemic this is a major achievement and required a lot of hard work! You have earnt a good break before your viva. Congratulations!

Disordered nanoisland surface plasmon sensor - paper published

15 Dec 2021: After some unfortunate covid delays, our experimental collaboration with Prof. Donghyun Kim and Hongki Lee from Yonsei University has born fruit! Read all about our work demonstrating single label free nanoparticle detection using random scattering of surface plasmons on a random nanoisland sensor, in our paper just published in Nanotechnology.

ICOEO and PIERS conferences postponed

8 Dec 2021: Due to recent covid outbreaks in China, both the ICOEO and PIERS conferences are postponed. This means you will unfortunately have to wait until 25-27 March 2022 and 25-29 April 2022 respectively to see talks from Niall and Matthew.

Recent publications

H. Lee, J. Berk, A. Webster, D. Kim and M. R. Foreman, "Label-free detection of single nanoparticles with disordered nanoisland surface plasmon sensor" Nanotechnology in press (2006).

Abstract : We report sensing of single nanoparticles using disordered metallic nanoisland substrates supporting surface plasmon polaritons (SPPs). Speckle patterns arising from leakage radiation of elastically scattered SPPs provides a unique fingerprint of the scattering microstructure at the sensor surface. Experimental measurements of the speckle decorrelation are presented and shown to enable detection of sorption of individual gold nanoparticles and polystyrene beads. Our approach is verified through bright-field and fluorescence imaging of particles adhering to the nanoisland substrate.

N. Byrnes and M. R. Foreman, "Polarisation statistics of vector scattering matrices from the circular orthogonal ensemble" Opt. Commun. 503, 127462 (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.

Funding

Our research is supported by generous funding from:

EPSRC
The Royal Society
Microsoft Research