Dynamics and timing-jitter of regenerative RF feedback assisted resonant electro-optic frequency comb

Abstract

Optical frequency combs have impacted a wide range of applications. The optical cavity assisted resonant electro-optic (EO) comb features broad spectral bandwidth and deterministic repetition-rate. However, the optical pulse timing-jitter is limited by the phase noise of the external RF drive source. To overcome this limitation at high repetition-rate, a regenerative RF feedback assisted resonant EO comb has been experimentally developed, which shows low phase noise of the regenerative RF drive signal. However, yet to date, the nonlinear dynamics and timing-jitter of the resonant EO comb coupled with a regenerative RF feedback loop remain unexplored. Here, for the first time, we quantitatively investigate the dynamics and timing-jitter of the resonant EO comb generation coupled with an optoelectronic oscillator (OEO). Our model indicates the detuning of the seed laser and EO comb cavity resonance determines the nonlinear feedback RF gain of OEO. Numerical simulations reveal the emergence of the bifurcation behaviors of the regenerative RF signal and the distinct EO comb formation dynamics with the increasing feedback RF gain of OEO, which provide the guidelines to achieve stable regenerative resonant EO comb. Moreover, in the presence of the noisy nonlinear feedback RF gain induced by the laser-cavity detuning fluctuations, our timing-jitter model predicts the seed laser frequency noise will be converted to the regenerative RF phase noise and optical pulse timing-jitter under the stable oscillation state of OEO. We highlight the mechanism of the transduction of laser frequency noise to the RF phase noise is differ from the Mach-Zehnder modulator based OEO. Experimentally, we attain a 10 GHz resonant EO comb generation with phase noise of −130 dBc/Hz at 10 kHz offset for the regenerative 10 GHz RF signal and optical pulse timing-jitter of 52.8 fs with an integral range from 100 Hz to 1 MHz. The experimental results agree well with the theoretical models. Our findings offer the solid guidelines for the design of the regenerative RF feedback assisted stable resonant EO comb with an optimized timing-jitter performance.