Super-efficient temporal solitons in mutually coupled optical cavities

A coherently driven Kerr optical cavity is able to sustain dissipative temporal solitons, enabling all-optical data storage buffers and broadband frequency combs. Kerr solitons are balanced through an energy exchange with the pump field. Improving the pump-to-soliton energy conversion is of great importance for practical applications, but remains an outstanding challenge owing to a limited pump–soliton temporal overlap. Here we report the discovery of temporal solitons in mutually coupled cavities instead of a traditional single cavity. A pump recycling strategy is proposed, to greatly improve the power utilization efficiency. Using macroscale optical fibre-ring cavities, which share the same physical model as miniature microresonators, we demonstrate nearly 100% pump recycling and the ability to break the efficiency limit of a single cavity. This study could greatly extend the applications of temporal cavity solitons and provides an attractive platform for exploring the complex nonlinear dynamics in coupled cavity systems. Efficient power transfer from the pump to the soliton can be achieved through field coupling between two optical resonators, allowing soliton frequency comb generation with tens-to-hundreds-of-fold improvement in conversion efficiency compared with a traditional single-resonator comb.