Double-chirping of the waveguide grating router

Although chirping only the arm lengths of the waveguide grating router allows each input-output port combination to have a dominant passband in one grating order with the peak transmissivities in other orders supressed, all but one of the dominant passbands necessarily have reduced peak transmissivities and increased widths, and the extraneous grating order passband suppression is limited. We show here that simultaneously chirping both the arm lengths and the angular distribution of the arms in one of the star couplers eliminates these deficiencies.