Photonic integrated wavelength-selective receivers based on tapered grating-assisted codirectional couplers

We report, for the first time, a tapered grating-assisted codirectional coupler (GACC) filter with a Hamming function coupling coefficient distribution achieved by varying the grating duty ratio. Using this novel filter design in an integrated wavelength-selective receiver, we demonstrated a device with record-low side-lobe levels. The integrated receiver was produced on InP/InGaAsP based materials via two MOCVD growths. It includes a 400 /spl mu/m semiconductor optical amplifier (SOA), two sections of tapered grating-assisted codirectional coupler (1300 /spl mu/m per section), and a 50 /spl mu/m waveguide photodetector. The top and bottom waveguide are made up of InGaAsP materials with band-gap wavelength of 1.4 /spl mu/m and 1.1 /spl mu/m, respectively. The GACC filter has a grating period of about 17 /spl mu/m. The filter and receiver were operated around 1.55 /spl mu/m. The one-stage Hamming-tapered filter shows a SSR of 11 dB which is lower than the theoretical SSR, 9 dB, of a uniform GACC filter.