Monolithic InP Stokes Vector Receiver with Multiple-Quantum-Well Photodetectors

Stokes vector modulation direct-detection (SVM-DD) formats have attained special attention in the short-reach communication links to transmit multilevel signals without using costly coherent receivers. In this paper, we fabricate and experimentally demonstrate a potentially low-cost DD-based SV receiver with on-chip photodetectors (PD) on a compact InP chip. Compressively strained multiple-quantum-well PD array is monolithically integrated with the SV projection circuit, which consists of multimode interference splitter and SV rotators based on self-aligned half-ridge structure. From the photocurrent signals at three on-chip PDs, the SV of input light is retrieved successfully over the entire Poincaré sphere. With potentially broad operating bandwidth of InP-based PDs, the demonstrated device may be an attractive candidate to realize low-cost and high-speed receivers for the future short-reach SVM-DD systems.