Recently learned from the University of Science and Technology of China, the university of Guo Guangcan academician team Professor Dong Chunhua and collaborator Zou Changling proposed a universal micro-cavity dispersion control mechanism, to achieve the real-time independent control of the optical frequency comb center frequency and repetition frequency, and applied to the precision measurement of optical wavelength, the wavelength measurement accuracy increased to kilohertz (kHz). The findings were published in Nature Communications.
Soliton microcombs based on optical microcavities have attracted great research interest in the fields of precision spectroscopy and optical clocks. However, due to the influence of environmental and laser noise and additional nonlinear effects in the microcavity, the stability of the soliton microcomb is greatly limited, which becomes a major obstacle in the practical application of the low light level comb. In previous work, the scientists stabilized and controlled the optical frequency comb by controlling the refractive index of the material or the geometry of the microcavity to achieve real-time feedback, which caused near-uniform changes in all resonance modes in the microcavity at the same time, lacking the ability to independently control the frequency and repetition of the comb. This greatly limits the application of the low-light comb in the practical scenes of precision spectroscopy, microwave photons, optical ranging, etc.

To solve this problem, the research team proposed a new physical mechanism to realize the independent real-time regulation of the center frequency and the repetition frequency of the optical frequency comb. By introducing two different micro-cavity dispersion control methods, the team can independently control the dispersion of different orders of micro-cavity, so as to achieve full control of different tooth frequencies of optical frequency comb. This dispersion regulation mechanism is universal to different integrated photonic platforms such as silicon nitride and lithium niobate, which have been widely studied.

The research team used the pumping laser and the auxiliary laser to independently control the spatial modes of different orders of the microcavity to realize the adaptive stability of the pumping mode frequency and the independent regulation of the frequency comb repetition frequency. Based on the optical comb, the research team demonstrated fast, programmable regulation of arbitrary comb frequencies and applied it to the precision measurement of wave length, demonstrating a wavemeter with a measurement accuracy of the order of kilohertz and the ability to measure multiple wavelengths simultaneously. Compared with the previous research results, the measurement accuracy achieved by the research team has reached three orders of magnitude improvement.

The reconfigurable soliton microcombs demonstrated in this research result lay the foundation for the realization of low-cost, chip integrated optical frequency standards, which will be applied in precision measurement, optical clock, spectroscopy and communication.