The generation of on-chip optical frequency combs in silicon-based charge injection modulators through strong phase modulation has been investigated as a prospective source for on-chip wavelength division multiplexing (WDM). Being CMOS-fabrication compatible, these modulators are easily integrated with other silicon photonic components. Resonant structure based implementations using PN-doped silicon micro-ring modulators have been used to generate frequency combs. However, in contrast to linear modulators, the use of such resonant structures leads to resonance shifts resulting from microwave induced thermal effects as well as causing a degradation in the quality of the modulator resonance. In this work, we report and investigate interesting effects observed as the optical and microwave power driving the comb generator is changed. We utilize a comb generator operating at a repetition rate of 10GHz and driven by optical powers in the range of 3mW to 30mW and microwave power in the range of 6dBm to 25dBm. We observe novel effects wherein the skewness of the comb envelope, the number of comb lines generated varies in a non-monotonic function with changes in optical power and DC bias. Abrupt transitions are reported from a broadband comb to no comb generation conditions with slight changes to drive RF powers. We attribute the variations to an interplay between the thermo-optic effects in the ring and its impact in moving the resonance of the ring with changing power.

Date Published: 4 March 2019
PDF: 7 pages
Proc. SPIE 10904, Laser Resonators, Microresonators, and Beam Control XXI, 109040S (4 March 2019); doi: 10.1117/12.2510898

Published in SPIE Proceedings Vol. 10904:
Laser Resonators, Microresonators, and Beam Control XXI
Alexis V. Kudryashov; Alan H. Paxton; Vladimir S. Ilchenko, Editor(s)