Abstract
We report on the experimental demonstration of an optical-fiber-integrated, nonvolatile transmission switching device. The operating mechanism exploits a cavity resonance spectral shift associated with an induced change in the refractive index of a high-index thin film on the polished side facet of the fiber. In the present case, a thermally induced amorphous-crystalline structural transition in a 500 nm layer of germanium antimony telluride at a distance of 500 nm from the core-cladding interface of an SMF-28 single-mode fiber delivers resonant transmission contrast >0.5 dB/mm at 1315 nm. Contrast is a function of active layer proximity to the core, while operating wavelength is determined by layer thickness—varying thickness by a few tens of nanometers can provide for tuning over the entire near-infrared telecoms spectral range.
Highlights
These can be integrated as thin film coatings deposited on the end facets or polished side-walls of step/graded-index fibers or on the internal surface(s) of hollow-core fibers.11–13 In the present case, we employ a side-polished fiber device geometry, wherein the cladding thickness over a short length of one side of the fiber is reduced such that the evanescent tail of the guided mode outside the core can interact with an external active medium or analyte at the remnant cladding surface
The operating mechanism exploits a cavity resonance spectral shift associated with an induced change in the refractive index of a high-index thin film on the polished side facet of the fiber
Contrast is a function of active layer proximity to the core, while operating wavelength is determined by layer thickness—varying thickness by a few tens of nanometers can provide for tuning over the entire near-infrared telecoms spectral range
Summary
These can be integrated as thin film coatings deposited on the end facets or polished side-walls of step/graded-index fibers or on the internal surface(s) of hollow-core fibers.11–13 In the present case, we employ a side-polished (or “D-shaped”) fiber device geometry, wherein the cladding thickness over a short length of one side of the fiber is reduced such that the evanescent tail of the guided mode outside the core can interact with an external active medium or analyte at (or in the optical near field of) the remnant cladding surface.
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