Integrated turnkey soliton microcombs operated at CMOS frequencies

TL;DR

This paper demonstrates a simplified, turnkey approach to operate soliton microcombs integrated with a pump laser at CMOS frequencies, eliminating complex control circuitry and enabling scalable production.

Contribution

It introduces a new operating regime for soliton microcombs that allows binary pump laser control, simplifying integration and reducing system complexity.

Findings

Achieved CMOS-rate microcombs with as low as 15 GHz frequency.

Demonstrated binary turn-on/turn-off pump laser operation for soliton generation.

Enabled fully integrated microcombs in a compact package.

Abstract

While soliton microcombs offer the potential for integration of powerful frequency metrology and precision spectroscopy systems, their operation requires complex startup and feedback protocols that necessitate difficult-to-integrate optical and electrical components. Moreover, CMOS-rate microcombs, required in nearly all comb systems, have resisted integration because of their power requirements. Here, a regime for turnkey operation of soliton microcombs co-integrated with a pump laser is demonstrated and theoretically explained. Significantly, a new operating point is shown to appear from which solitons are generated through binary turn-on and turn-off of the pump laser, thereby eliminating all photonic/electronic control circuitry. These features are combined with high-Q $Si_3N_4$ resonators to fully integrate into a butterfly package microcombs with CMOS frequencies as low as 15 GHz, offering compelling advantages for high-volume production.