“…Yet, to date, direct soliton interactions, including shortrange binding [19,20] and collision [21,22], have not been thoroughly investigated in DKSs, despite the fact that they hold critical importance, not only for understanding the fundamental soliton dynamics, but also for applications such as a vernier spectrometer using counterpropagating DKSs [23], as well as tricomb spectroscopy [24] with spatial multiplexing of DKSs [25]. The difficulty is threefold: first, solitons pumped by the same lasers have the same group velocity, which makes the control of the relative locations of solitons difficult; second, because of the low output power and the high repetition rate of microresonator DKSs, commonly employed imaging techniques including dispersive Fourier transformation technique [26] and electro-optic imaging technique [27] cannot be applied to image the close interaction of similar DKSs due to the limited temporal window or the coarse resolution; third, because of internal disturbances such as mode crossings [28], DKSs usually interact with other DKSs via long-range dispersive-wave-mediated effects [29][30][31][32], forming groups with large intersoliton separations, thus prohibiting the inception of direct binding and collision.…”