Large Dispersion Silicon Bragg Grating for Full-Field 40-GBd QPSK Phase Retrieval Receiver

Optical devices that introduce and compensate for dispersion serve an important role in communication networks, photonic signal processing, and nonlinear optics. In this article, we demonstrate a silicon photonic Bragg grating which simultaneously achieves a large dispersion and wide bandwidth. We measure the grating to have a dispersion of −146 ps/nm over a 171 GHz bandwidth, representing the highest demonstrated grating dispersion over this wide bandwidth in a standard thickness silicon photonics process. Additionally, we show a significant reduction of group delay ripple by tuning the grating using an integrated phase shifter array to address fabrication variations. We further use the silicon grating as a dispersive element in a direct-detection phase retrieval receiver for 40 GBd quadrature phase shift keying (QPSK) signals and achieve a bit error rate (BER) below the 20% forward error correction (FEC) threshold. These results establish the potential for scalable silicon photonic circuits leveraging large dispersion for optical communication and other applications.