Cladding-mode resonances in hybrid polymer-silica microstructured optical fiber gratings

We examine the cladding-mode resonances of fiber gratings UV written into the core of a novel microstructured fiber whose air regions are subsequently infused with polymer. The cladding spectrum changes with temperature because of the strong temperature dependence of the polymer refractive index and we show that these changes can be understood qualitatively using a simple model of the polymer-silica waveguide. Our results imply wavelength and amplitude tuning regimes for long period gratings written into this fiber with tunability enhanced over conventional long period gratings because of the small effective inner cladding diameter of our fiber.