Spur-Free Dynamic Range Measurements of a Traveling Wave Mach-Zehnder Carrier Depletion Silicon Modulator

Abstract

An outstanding question has been whether the analog performance of silicon components can compete with conventional optical material systems such as Lithium Niobate. A key challenge for silicon photonics is the fact that most modulators, including the one reported here, are based on a reverse biased PN junction. PN junctions exhibit significant nonlinearities, and it has thus been unclear whether analog performance in the silicon platform could ever compete with what has been achieved with Lithium Niobate based modulators. Characterized here is one of the key metrics for analog performance, the Spur Free Dynamic Range (SFDR). This is a measure of the degree of nonlinear cross-talk between different frequencies propagating in a single system. With the proper device configuration, this work shows that the SFDR of a silicon modulator can approach that of Lithium Niobate based systems. In particular, this modulator achieves 104.5 dB·Hz2/3 SFDR for IMD, which is within 15 dB of the best result in Lithium Niobate, 120.5 dB·Hz2/3. This level of performance is also already sufficient for a number of analog applications, including WLAN. The paths to improving this value are also briefly discussed; there are a number of reasons to believe that performance in integrated silicon photonic systems can be improved in the future, and likely match the performance seen in the very best optical systems for analog links.