[1] T. Udem, R. Holzwarth, T. W. Hänsch. Optical frequency metrology. Nature, 416, 233-237(2002).
[27] S. H. Lee, D. Y. Oh, Q.-F. Yang, B. Shen, H. Wang, K. Y. Yang, Y. H. Lai, X. Yi, K. Vahala. Towards visible soliton microcomb generation(2017).
[28] X. Guo, C.-L. Zou, H. Jung, Z. Gong, A. Bruch, L. Jiang, H. X. Tang. Efficient visible frequency comb generation via Cherenkov radiation from a Kerr microcomb(2017).