Time-reversal constraint limits unidirectional photon emission in slow-light photonic crystals

Ben Lang*, Daryl M Beggs, Ruth Oulton

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

9 Citations (Scopus)
330 Downloads (Pure)


Photonic crystal waveguides are known to support C-points - point-like polarisation singularities with local chirality. Such points can couple with dipole-like emitters to produce highly directional emission, from which spin-photon entanglers can be built. Much is made of the promise of using slowlight modes to enhance this light-matter coupling. Here we explore the transition from travelling to standing waves for two different photonic crystal waveguide designs. We find that time-reversal symmetry and the reciprocal nature of light places constraints on using C-points in the slow-light regime. We observe two distinctly different mechanisms through which this condition is satisfied in the two waveguides. In the waveguide designs we consider, a modest group-velocity of vg ≈ c/10 is found to be the optimum for slow-light coupling to the C-points.
Original languageEnglish
Article number20150263
Number of pages11
JournalPhilosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Issue number2075
Publication statusPublished - 28 Aug 2016

Structured keywords

  • QETLabs


  • Photonic crystal
  • Polarization
  • Polarization singularities
  • Slow light
  • Waveguide


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