Tailoring chirp characteristics of waveguide Bragg gratings using tapered core profiles

We propose and demonstrate the design principle of tapered core profiles for tailoring the chirp characteristics of waveguide Bragg grating (WBG) devices with uniform grating periods. Based on both numerical and experimental approaches, we establish the dependence of the modal effective index on the core width. We then design and fabricate polymeric WBG devices with a taper profile optimized for a linear group delay and those with a linear taper as well. Although they exhibit high ripples in their spectral responses due to incomplete structures, their chirp characteristics fit well the expected group delay curves.