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Lower bound for the spatial extent of localized modes in photonic-crystal waveguides with small random imperfections

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  • Rémi Faggiani
  • Alexandre Baron
  • Xiaorun Zang
  • Loïc Lalouat
  • Sebastian A. Schulz
  • Bryan O'Regan
  • Kevin Vynck
  • Benoît Cluzel
  • Frédérique De Fornel
  • Thomas F. Krauss
  • Philippe Lalanne


Publication details

JournalScientific Reports
DateAccepted/In press - 21 Mar 2016
DateE-pub ahead of print (current) - 1 Jun 2016
Early online date1/06/16
Original languageEnglish


Light localization due to random imperfections in periodic media is paramount in photonics research. The group index is known to be a key parameter for localization near photonic band edges, since small group velocities reinforce light interaction with imperfections. Here, we show that the size of the smallest localized mode that is formed at the band edge of a one-dimensional periodic medium is driven instead by the effective photon mass, i.e. the flatness of the dispersion curve. Our theoretical prediction is supported by numerical simulations, which reveal that photonic-crystal waveguides can exhibit surprisingly small localized modes, much smaller than those observed in Bragg stacks thanks to their larger effective photon mass. This possibility is demonstrated experimentally with a photonic-crystal waveguide fabricated without any intentional disorder, for which near-field measurements allow us to distinctly observe a wavelength-scale localized mode despite the smallness (∼1/1000 of a wavelength) of the fabrication imperfections.

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