“…Before the exploration of the optical Kerr efect in whispering-gallery-mode resonators, optical frequency combs were developed from mode-locked lasers. Nowadays, optical frequency combs have also found much border sources such as continuous lasers [8], optical fbers [9], optoelectronic oscillators [10,11], and more [1,7,12]. However, in 2004, two independent teams generated optical frequency combs for the frst time through amorphous [13] and crystalline [14] whispering-gallery-mode resonators.…”