Thermal tuning of Kerr frequency combs in silicon nitride microring resonators

• Published in: Optics express Vol. 24; no. 1; pp. 687 - 698
• Main Authors: Xue, Xiaoxiao, Xuan, Yi, Wang, Cong, Wang, Pei-Hsun, Liu, Yang, Niu, Ben, Leaird, Daniel E, Qi, Minghao, Weiner, Andrew M
• Format: Journal Article
• Language: English
• Published: United States 11.01.2016
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/oe.24.000687

Microresonator based Kerr frequency comb generation has many attractive features, including ultrabroad spectra, chip-level integration, and low power consumption. Achieving precise tuning control over the comb frequencies will be important for a number of practical applications, but has been little explored for microresonator combs. In this paper, we characterize the thermal tuning of a coherent Kerr frequency comb generated from an on-chip silicon nitride microring. When the microring temperature is changed by ~70 °C with an integrated microheater, the line spacing and center frequency of the comb are tuned respectively by -253 MHz (-3.57 MHz/°C) and by -175 GHz (-2.63 GHz/°C); the latter constitutes 75% of the comb line spacing. From these results we obtain a shift of 25 GHz (362.07 MHz/°C) in the comb carrier-envelope offset frequency. Numerical simulations are performed by taking into account the thermo-optic effects in the waveguide core and cladding. The temperature variation of the comb line spacing predicted from simulations is close to that observed in experiments. The time-dependent thermal response of the microheater based tuning scheme is characterized; time constants of 30.9 μs and 0.71 ms are observed.