Solitons occur in many physical systems when a nonlinearity compensates wave dispersion. Their recently demonstrated formation in microresonators has opened a new research direction for nonlinear optical physics^1,2,3,4,5. Soliton mode locking also endows frequency microcombs with the enhanced stability necessary for miniaturization of spectroscopy and frequency metrology systems⁶. These microresonator solitons orbit around a closed waveguide path and produce a repetitive output pulse stream at a rate set by the roundtrip time. Here, counter-propagating solitons that simultaneously orbit in an opposing sense (clockwise/counter-clockwise) are studied. Despite sharing the same spatial mode family, their roundtrip times can be precisely and independently controlled. Furthermore, a state is possible in which both the relative optical phase and relative repetition rates of the distinct soliton streams are locked. This state allows a single resonator to produce dual-soliton frequency-comb streams with different repetition rates, but with a high relative coherence that is useful in both spectroscopy^7,8,9 and laser ranging systems¹⁰.

当非线性补偿波色散时，孤子会在许多物理系统中出现。它们最近在微谐振器中的形成为非线性光学物理学^1,2,3,4,5开辟了新的研究方向。孤子模式锁定还使频率微梳具有增强的稳定性，这对于光谱学和频率计量系统的小型化是必不可少的⁶。这些微谐振器孤子围绕闭合的波导路径运行，并以往返时间设置的速率产生重复的输出脉冲流。在这里，研究了以相反的方向（顺时针/逆时针）同时旋转的反向传播的孤子。尽管共享相同的空间模式族，但是它们的往返时间可以精确且独立地控制。此外，可能存在不同的孤子流的相对光学相位和相对重复率都被锁定的状态。这种状态允许单个谐振器产生具有不同重复率但具有较高相对相干性的双孤子频率梳流，这在光谱^7、8、9和激光测距系统¹⁰中均有用。