Stimulus-responsive light coupling and modulation with nanofiber waveguide junctions

Ilsun Yoon, Kanguk Kim, Sarah E. Baker, Daniel Heineck, Sadik C. Esener, Donald J. Sirbuly

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


We report a systematic study of light coupling at junctions of overlapping SnO 2 nanofiber waveguides (WGs) as a function of gap separation and guided wavelength. The junctions were assembled on silica substrates using micromanipulation techniques and the gap separation was controlled by depositing thin self-assembled polyelectrolyte coatings at the fiber junctions. We demonstrate that the coupling efficiency is strongly dependent on the gap separation, showing strong fluctuations (0.1 dB/nm) in the power transfer when the separation between nanofibers changes by as little as 2 nm. Experimental results correlate well with numerical simulations using three-dimensional finite-difference time-domain techniques. To demonstrate the feasibility of using coupled nanofiber WGs to modulate light, we encased the junctions in an environment-responsive matrix and exposed the junctions to gaseous vapor. The nanofiber junctions show an ∼95% (or ∼80%) modulation of the guided 450 nm (or 510 nm) light upon interaction with the gaseous molecules. The results reveal a unique nanofiber-based sensing scheme that does not require a change in the refractive index to detect stimuli, suggesting these structures could play important roles in localized sensing devices including force-based measurements or novel chemically induced light modulators.

Original languageEnglish (US)
Pages (from-to)1905-1911
Number of pages7
JournalNano Letters
Issue number4
StatePublished - Apr 11 2012
Externally publishedYes


  • Semiconductor nanowire
  • evanescent field
  • light modulation
  • nanophotonics
  • sensor
  • subwavelength waveguide

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering


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