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

Optical devices that introduce and compensate for dispersion are critical for communication networks, photonic signal processing, and nonlinear optics. In this paper, 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 dispersion over a 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.