New design and analysis of Bragg grating waveguides.

New design of optical waveguides is presented to synthesize Bragg grating waveguides without inducing birefringence. In the design, waveguide core has a thin trench on the top surface of the core and width of the trench is modulated concurrently with width modulation of the waveguide core. Effective refractive index profiles in Bragg grating waveguides are obtained by a differential inverse scattering algorithm and converted to waveguide width profiles by using the new core design. This procedure allows design of non-birefringent Bragg grating waveguides on planar substrate. The method is applied to the design of chromatic dispersion compensators. For characterization of Bragg grating waveguides, analysis based on short-time Fourier transform of Bragg grating response waveforms is presented.