  Rapid progress in photonics has led to an explosion of integrated devices
that promise to deliver the same performance as table-top technology at the
nanoscale; heralding the next generation of optical communications, sensing and
metrology, and quantum technologies. However, the challenge of co-integrating
the multiple components of high-performance laser systems has left application
of these nanoscale devices thwarted by bulky laser sources that are orders of
magnitude larger than the devices themselves. Here we show that the two main
ingredients for high-performance lasers -- noise reduction and isolation --
currently requiring serial combination of incompatible technologies, can be
sourced simultaneously from a single, passive, CMOS-compatible nanophotonic
device. To do this, we take advantage of both the long photon lifetime and the
nonreciprocal Kerr nonlinearity of a high quality factor silicon nitride ring
resonator to self-injection lock a semiconductor laser chip while also
providing isolation. Additionally, we identify a previously unappreciated power
regime limitation of current on-chip laser architectures which our system
overcomes. Using our device, which we term a unified laser stabilizer, we
demonstrate an on-chip integrated laser system with built-in isolation and
noise reduction that operates with turnkey reliability. This approach departs
from efforts to directly miniaturize and integrate traditional laser system
components and serves to bridge the gap to fully integrated optical
technologies.
