Directly pumped 10 GHz microcomb modules from low-power diode lasers.

Soliton microcombs offer the prospect of advanced optical metrology and timing systems in compact form factors. In these applications, the pumping of microcombs directly from a semiconductor laser without amplification or triggering components is desirable to reduce system power and to simplify system design. At the same time, low-repetition-rate microcombs are required in many comb applications as an interface to detectors and electronics, but their increased mode volume makes them challenging to pump at low power. Here 10 GHz repetition rate soliton microcombs are directly pumped by low-power (<20  mW) diode lasers. High-Q silica microresonators are used for this low-power operation and are packaged into fiber-connectorized modules that feature temperature control for improved long-term frequency stability.