Separable integrated frequency control of a microcomb

This paper introduces a method for separable integrated frequency control of microcombs, enabling independent control over both the offset frequency and the repetition rate of the comb. The approach leverages a novel integrated actuation mechanism, which decouples the two parameters, offering high precision and efficiency.

Key points include:

1. Separable Control Mechanism: The method uses a coupled-ring resonator with a frequency vernier to achieve independent tuning of the offset frequency (ν0) and the repetition rate (frep) of a microcomb. This is done via common-mode and differential-mode tuning, leveraging the Moiré speed-up effect to isolate and independently control the two parameters.

2. Experimental Demonstration: The microcomb was frequency-locked to a high-stability Fabry-Pérot cavity, demonstrating its utility in applications such as high-resolution spectroscopy and microwave generation. The system achieved a cross-talk rejection greater than 40 dB up to 10 kHz frequency offset, with a fast response bandwidth exceeding 1 MHz.

3. Piezoelectric Actuation: The tuning mechanism utilizes integrated piezoelectric actuators, which provide MHz-level control. The actuators enable bidirectional, linear tuning of the microcomb, offering precision without introducing unwanted crosstalk between the two parameters.

4. Frequency Stabilization: The microcomb was fully stabilized by locking its offset frequency and repetition rate to reference lasers. This stabilization was achieved using piezoelectric actuators and demonstrated by the low phase noise in the beat frequency between the comb and the reference laser.

5. Applications: The fully stabilized microcomb is used for high-resolution spectroscopy, optical frequency division, and microwave synthesis, making it suitable for applications in quantum optics, telecommunications, and other precision measurement fields.

In conclusion, this paper presents a novel, integrated approach for frequency control in microcombs, significantly improving their performance and applicability in various scientific and technological applications.