Demonstration of InP-InGaAsP vertical grating-assisted codirectional coupler filters and receivers with tapered coupling coefficient distributions

In this letter, we demonstrate the first vertical grating-assisted codirectional coupler filter and receiver with a tapered coupling coefficient distribution. The tapering is achieved by modulating the grating duty ratio. By doing so, filter responses with sidelobe suppression ratios (SSR) better than conventional devices are observed. Using this design in an integrated receiver, a record SSR of 16 dB is reported. With perfect input coupling, it is found that the receiver sidelobe levels using this approach can be lower than /spl sim/40 dB.