Soliton microcomb generation by cavity polygon modes

Soliton microcombs, which require the hosting cavity to operate in an anomalous dispersion regime, are essential to integrate photonic systems. In the past, soliton microcombs were generated on cavity whispering gallery modes (WGMs), and the anomalous dispersion requirement of the cavity made by normal dispersion material was achieved through structural dispersion engineering. This inevitably degrades the cavity optical quality factor (Q) and increases pump threshold power for soliton comb generation. To overcome the challenges, here, we report a soliton microcomb excited by cavity polygon modes. These modes display anomalous dispersion at near-infrared while optical Q factors exceeding 4×10⁶ are maintained. Consequently, a soliton comb spanning from 1450 nm to 1620 nm with a record low pump power of 11 mW is demonstrated, a three-fold improvement compared to the state of the art on the same material platform.