  Advances in microresonator-based soliton generation promise chip-scale
integration of optical frequency comb for applications spanning from time
keeping to frequency synthesis. Miniaturized cavities harness Kerr nonlinearity
and enable terahertz soliton repetition rates. However, such high repetition
rates are not amenable to direct electronic detection. Here, we demonstrate
hybrid Kerr and electro-optic microcombs using the lithium niobate thin film
that exhibits both Kerr and Pockels nonlinearities. By interleaving the
high-repetition-rate Kerr soliton comb with the low-repetition-rate
electro-optic comb on the same waveguide, the wide Kerr soliton mode spacing is
divided within a single chip, allowing for subsequent electronic detection and
feedback control of the soliton repetition rate. Our work establishes an
integrated electronic interface to Kerr solitons of terahertz repetition rates,
paving the path towards chipscale optical-to-microwave frequency division and
comb locking.
