Postgraduate research opportunities Ultrahigh Gain Thin Films


Key facts

  • Opens: Thursday 26 July 2018
  • Number of places: 1


The project will study the properties of amplifying and nonlinear films both analytically and numerically. Collaboration with an experimental team at the University of Glasgow will also be exploited.
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BSc (Hons) 2:1 or equivalent degree in physics


Scholarships (fees and stipend) available on a competitive basis for UK students, please contact supervisor for details.

THE Awards 2019: UK University of the Year Winner
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Project Details

In sub-wavelength lossy optical films the amount of loss experienced by an optical mode can depend upon the input mode of the light. For a 50% lossy film the loss can be modulated from 0 to 100%. This phenomenon is known as coherent perfect absorption[1, 2, 3]. Quantum effects have also been observed, the most striking of which is the deterministic absorption of one photon from an entangled photon pair, rendering the loss of photons a nonrandom process [1, 4].

A direct translation of this effect to amplifying films leads to coherent amplification, in which an optical medium can exhibit a gain of anything between 1 and (theoretically) infinity. In realistic systems with a finite number of gain centres the gain is limited by the maximum number of added photons. A sub-wavelength film naturally has a small number of gain centres.

Epsilon near zero materials are optical media whose relative permittivity is very small and hence a slab of such a material would have a very small optical propagation phase. They can therefore be used to mimic thin films whilst still being of macroscopic thickness. If such a “thin” film were doped with amplifying centres a very high gain could in principle be reached.

Furthermore, in epsilon near zero materials the nonlinear coefficients are typically very high, as the near zero permittivity appears in the denominator of the nonlinear coefficients. If we use these two properties, the high nonlinear coefficients and the enormous gain available in thin films, we can envisage reaching ultrahigh nonlinear gains in such devices. Given that one limitation in quantum optics and communication is the difficulty of producing nonclassical states of light, such a device would be a significant step forward.

  • [1] J. Jeffers, Interference and the lossless lossy beam splitter, Journal of Modern Optics, 47:11, 1819-1824 (2000).
  • [2] W. Wan, Y. D. Chong, L. Ge, H. Noh, A. D. Stone, and H. Cao, Science 331, 889 (2011).
  • [3] T. Roger et al, Coherent perfect absorption in deeply subwavelength films in the single-photon regime, Nature Communications 6, 7031 (2015).
  • [4] T. Roger, S. Restuccia, A. Lyons, D. Giovannini, J. Romero, J. Jeffers, M. Padgett, and D. Faccio, Coherent Absorption of N00N States, PRL 117, 023601 (2016).
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Professor John Jeffers


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In the first instance, please direct enquiries to Prof. John Jeffers (

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