High-speed actuation of laser frequency1 is critical in applications using lasers and frequency combs2,3, and is a prerequisite for phase locking, frequency stabilization and stability transfer among optical carriers. For example, high-bandwidth feedback control of frequency combs is used in optical-frequency synthesis4, frequency division5 and optical clocks6. Soliton microcombs7,8 have emerged as chip-scale frequency comb sources, and have been used in system-level demonstrations9,10. Yet integrated microcombs using thermal heaters have limited actuation bandwidths11,12 of up to 10 kilohertz. Consequently, megahertz-bandwidth actuation and locking of microcombs have only been achieved with off-chip bulk component modulators. Here we demonstrate high-speed soliton microcomb actuation using integrated piezoelectric components13. By monolithically integrating AlN actuators14 on ultralow-loss Si3N4 photonic circuits15, we demonstrate voltage-controlled soliton initiation, tuning and stabilization with megahertz bandwidth. The AlN actuators use 300 nanowatts of power and feature bidirectional tuning, high linearity and low hysteresis. They exhibit a flat actuation response up to 1 megahertz—substantially exceeding bulk piezo tuning bandwidth—that is extendable to higher frequencies by overcoming coupling to acoustic contour modes of the chip. Via synchronous tuning of the laser and the microresonator, we exploit this ability to frequency-shift the optical comb spectrum (that is, to change the comb’s carrier-envelope offset frequency) and make excursions beyond the soliton existence range. This enables a massively parallel frequency-modulated engine16,17 for lidar (light detection and ranging), with increased frequency excursion, lower power and elimination of channel distortions resulting from the soliton Raman self-frequency shift. Moreover, by modulating at a rate matching the frequency of high-overtone bulk acoustic resonances18, resonant build-up of bulk acoustic energy allows a 14-fold reduction of the required driving voltage, making it compatible with CMOS (complementary metal–oxide–semiconductor) electronics. Our approach endows soliton microcombs with integrated, ultralow-power and fast actuation, expanding the repertoire of technological applications of microcombs. By monolithically integrating piezoelectric actuators on ultralow-loss photonic circuits, soliton microcombs—a spectrum of sharp lines over a range of optical frequencies—can be modulated at high speeds with megahertz bandwidths.

中文翻译：

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孤子微梳的单片压电控制

激光频率的高速驱动 1 在使用激光和频率梳 2、3 的应用中至关重要，并且是光学载波之间锁相、频率稳定和稳定性传输的先决条件。例如，频率梳的高带宽反馈控制用于光频合成4、分频5和光时钟6。孤子微梳 7、8 已作为芯片级频率梳源出现，并已用于系统级演示 9、10。然而，使用热加热器的集成微梳具有高达 10 kHz 的有限驱动带宽 11,12。因此，只有使用片外体组件调制器才能实现兆赫兹带宽驱动和微梳锁定。在这里，我们演示了使用集成压电元件的高速孤子微梳驱动。通过在超低损耗 Si3N4 光子电路上单片集成 AlN 致动器 15，我们展示了具有兆赫带宽的压控孤子启动、调谐和稳定。AlN 执行器使用 300 纳瓦的功率，并具有双向调谐、高线性度和低滞后性。它们表现出高达 1 兆赫的平坦驱动响应——大大超过了体压电调谐带宽——通过克服与芯片声学轮廓模式的耦合，可扩展到更高的频率。通过激光器和微谐振器的同步调谐，我们利用这种能力对光梳光谱进行频移（即改变梳的载波包络偏移频率）并使偏移超出孤子存在范围。这可以实现大规模并行调频引擎16，17 用于激光雷达（光检测和测距），具有增加的频率偏移、更低的功率和消除由孤子拉曼自频移引起的通道失真。此外，通过以匹配高泛音体声共振频率的速率进行调制，体声能量的共振积累可以将所需的驱动电压降低 14 倍，使其与 CMOS（互补金属氧化物半导体） 电子产品。我们的方法赋予孤子微梳集成、超低功耗和快速驱动，扩展了微梳的技术应用范围。通过在超低损耗光子电路上单片集成压电致动器，