Kerr microresonators generate interesting and useful fundamental states of
electromagnetic radiation through nonlinear interactions of continuous-wave
(CW) laser light. Using photonic-integration techniques, functional devices
with low noise, small size, low-power consumption, scalable fabrication, and
heterogeneous combinations of photonics and electronics can be realized. Kerr
solitons, which stably circulate in a Kerr microresonator, have emerged as a
source of coherent, ultrafast pulse trains and ultra-broadband
optical-frequency combs. Using the f-2f technique, Kerr combs support
carrier-envelope-offset phase stabilization for optical synthesis and
metrology. In this paper, we introduce a Kerr-microresonator optical clockwork
based on optical-frequency division (OFD), which is a powerful technique to
transfer the fractional-frequency stability of an optical clock to a lower
frequency electronic clock signal. The clockwork presented here is based on a
silicon-nitride (Si3​N4​) microresonator that supports an optical-frequency
comb composed of soliton pulses at 1 THz repetition rate. By electro-optic
phase modulation of the entire Si3​N4​ comb, we arbitrarily generate
additional CW modes between the Si3​N4​ comb modes; operationally, this
reduces the pulse train repetition frequency and can be used to implement OFD
to the microwave domain. Our experiments characterize the residual frequency
noise of this Kerr-microresonator clockwork to one part in 1017, which
opens the possibility of using Kerr combs with high performance optical clocks.
In addition, the photonic integration and 1 THz resolution of the Si3​N4​
frequency comb makes it appealing for broadband, low-resolution liquid-phase
absorption spectroscopy, which we demonstrate with near infrared measurements
of water, lipids, and organic solvents