Chromatic focal plane displacement in the parabolic chirped waveguide grating router

It is shown that the application of parabolic chirp to the arm lengths of the waveguide grating router is equivalent to placing a lens with chromatic aberration in the free-space region. By adjusting the focal plane for each port, performance equivalent to a nonchirped grating can be achieved in a desired grating order with significant passband suppression in unwanted grating orders.