A High Spur-Free Dynamic Range Silicon DC Kerr Ring Modulator for RF Applications

Silicon photonics offer a low-cost platform for large-scale RF system integration. Spur-free dynamic range (SFDR) for analog and RF photonic components is limited by electrical and optical characteristics of the p- and n- junction used to produce plasma dispersion. We propose a silicon ring modulator and demonstrate design conditions that balance the phase change between the DC Kerr and plasma dispersion effects to produce a broadband, linear electro-optical conversion. A linear phase shifter is tested within a ring modulator and an SFDR of 98 dB $\cdot$ Hz $^{2/3}$ is measured. With predistortion, the SFDR increases to 108 dB $\cdot$ Hz $^{2/3}$ . In addition, the ring supports discrete multitone modulation with 16-QAM subcarriers at a 47 Gbps data rate over a 16 GHz bandwidth.