  Driven by narrow-linewidth bench-top lasers, coherent optical systems
spanning optical communications, metrology and sensing provide unrivalled
performance. To transfer these capabilities from the laboratory to the real
world, a key missing ingredient is a mass-produced integrated laser with
superior coherence. Here, we bridge conventional semiconductor lasers and
coherent optical systems using CMOS-foundry-fabricated microresonators with
record high $Q$ factor over 260 million and finesse over 42,000. Five
orders-of-magnitude noise reduction in the pump laser is demonstrated, and for
the first time, fundamental noise below 1 Hz$^2$ Hz$^{-1}$ is achieved in an
electrically-pumped integrated laser. Moreover, the same configuration is shown
to relieve dispersion requirements for microcomb generation that have
handicapped certain nonlinear platforms. The simultaneous realization of
record-high $Q$ factor, highly coherent lasers and frequency combs using
foundry-based technologies paves the way for volume manufacturing of a wide
range of coherent optical systems.
