Coupling coefficient modulation of waveguide grating using sampled grating

A new method of modulating the coupling coefficient along the waveguide is proposed. The effect of our method, which uses a nonperiodic sampled grating, is demonstrated both theoretically and experimentally. A Bragg filter is fabricated on an InGaAsP/InP wafer utilizing the method, and the sidelobe level is shown to improve by 7 dB compared with a conventional filter with a uniform coupling coefficient. The experimental results are found to be in good agreement with calculations.>