title: Stimulus-responsive light coupling and modulation with nanofiber waveguide junctions.
abstract: 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.
authors.affiliation: Department of NanoEngineering, University of California, San Diego, La Jolla, California 92093, USA.
authors.forename: Ilsun
authors.initials: I
authors.lastname: Yoon
authors.forename: Kanguk
authors.initials: K
authors.lastname: Kim
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Baker
authors.forename: Daniel
authors.initials: D
authors.lastname: Heineck
authors.forename: Sadik C
authors.initials: SC
authors.lastname: Esener
authors.forename: Donald J
authors.initials: DJ
authors.lastname: Sirbuly
mesh_terms: D004129:Dimethylpolysiloxanes / Q000737:chemistry; D008027:Light; D057139:Nanofibers / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry; D017971:Tin Compounds / Q000737:chemistry*
chemical_list: D004129:Dimethylpolysiloxanes; D017971:Tin Compounds; C013830:baysilon; D012822:Silicon Dioxide; C045358:stannic oxide