By generating a Brillouin laser in an optical microresonator, we realize a soliton Kerr microcomb through exciting the Kerr frequency comb using the generated Brillouin laser in the same cavity. The intracavity Brillouin laser pumping scheme enables us to access the soliton states with a blue-detuned input pump. Due to the ultra-narrow linewidth and the low-noise properties of the generated Brillouin laser, the observed soliton microcomb exhibits narrow-linewidth comb lines and stable repetition rate even by using a diode laser with relatively broad linewidth. Also, we demonstrate a low-noise microwave signal with phase noise levels of -24 dBc/Hz at 10 Hz, -111 dBc/Hz at 10 kHz, and -147 dBc/Hz at 1 MHz offsets for a 11.14 GHz carrier with only a free-running input pump. The easy operation of the Brillouin-Kerr soliton microcomb with excellent performance makes our scheme promising for practical applications.

Realization of chip-scale nonreciprocal optics such as isolators and circulators is highly demanding for all-optical signal routing and protection with standard photonics foundry process. Owing to the significant challenge for incorporating magneto-optical materials on chip, the exploration of magnetic-free alternatives has become exceedingly imperative in integrated photonics. Here, a chip-based, tunable all-optical isolator at the telecommunication band is demonstrated, which is based upon bulk stimulated Brillouin scattering (SBS) in a high-Q silica microtoroid resonator. This device exhibits remarkable characteristics over most state-of-the-art implements, including high isolation ratio, no insertion loss, and large working power range. Thanks to the guided acoustic wave and accompanying momentum-conservation condition, bulk SBS also assist in realizing the nonreciprocal parity-time symmetry in two directly coupled microresonators. The breach of time-reversal symmetry further makes the design a versatile arena for developing many formidable ultra-compact devices such as unidirectional single-mode Brillouin lasers and supersensitive photonic sensors.

No abstract