Abstract
We report on the fabrication of a superstructure Bragg grating in a planar polymer substrate. Based on a twofold illumination process an integrated waveguide and a superstructure Bragg grating are subsequently written into bulk polymethylmethacrylate by UV-induced refractive index modification. The measured reflected spectrum of the superstructure Bragg grating exhibits multiple reflection peaks and is in good agreement with performed standard simulations based on the beam propagation method and coupled mode theory algorithms. By applying a varying tensile load we determine the strain sensitivity to be about 1.10 pm/µε and demonstrate the applicability of the superstructure Bragg grating for strain measurements with redundant sensing signals.
Highlights
Bragg gratings are wavelength-selective filters that are based on a periodical refractive index perturbation inside an optical waveguide
We already demonstrated that polymer planar Bragg gratings (PPBG) which are written using a single writing step can be applied for different sensing applications like measuring temperature, relative humidity, or tensile and compressive strain [12,13,14,15]
We describe the spectral of superstructure Bragg gratings in bulk polymer substrates
Summary
Bragg gratings are wavelength-selective filters that are based on a periodical refractive index perturbation inside an optical waveguide. A more effective approach to obtain a reflected spectrum with multiple reflection peaks is the fabrication of superstructure Bragg gratings These devices have successfully been created in germanosilicate planar waveguides and applied for WDM applications [6,7]. Sparrow et al reported on integrated superstructure gratings in planar silica on silicon substrates [8] All these devices are based on silica, while polymer materials are rarely used. We already demonstrated that polymer planar Bragg gratings (PPBG) which are written using a single writing step can be applied for different sensing applications like measuring temperature, relative humidity, or tensile and compressive strain [12,13,14,15].
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