Slow light via a tapered grating: transfer matrix approach

Reflection properties of a nonuniform apodized Bragg grating connecting a homogeneous medium with a (half-infinite) uniform grating are investigated for system parameters such that the group velocity in the uniform grating is low. In particular a smooth polynomial transition of the index profile to the uniform region is considered. Exact coupled mode equations for local Bloch amplitudes are set up in a transfer matrix formalism. For a linear taper the coupling matrix appears to be singular for parameter values near the edge of the photonic band gap. The polynomial profile removes the singularity in this coupling term.