Silicon Photonics Phase and Intensity Modulators for Flat Frequency Comb Generation

Flat electro-optical frequency combs play an important role in a wide range of applications,such as metrology,spectroscopy,or microwave photonics.As a key technology for the integration of optical circuits,silicon photonics could benefit from on-chip,tunable,flat frequency comb generators.In this article,two different architectures based on silicon modulators are studied for this purpose.They rely on a time to frequency conversion principle to shape the comb envelope.Using a numerical model of the silicon traveling-wave phase modulators,their driving schemes are optimized before their performances are simulated and compared.A total of nine lines could be obtained within a 2 dB flatness,with a line-spacing ranging from 0.1 to 7 GHz.Since this tunability is a major asset of electro-optical frequency combs,the effect of segmenting the phase modulators is finally investigated,showing that the flat lines spacing could be extended up to 39 GHz by this method.