Integrated photonics enables signal synthesis, modulation and conversion using photonic integrated circuits (PICs). Many materials have been developed, among which silicon nitride (Si₃N₄) has emerged as a leading platform particularly for nonlinear photonics. Low-loss Si₃N₄ PICs have been widely used for frequency comb generation, narrow-linewidth lasers, microwave photonics and photonic computing networks. Yet, among all demonstrated functionalities for Si₃N₄ integrated photonics, optical non-reciprocal devices such as isolators and circulators have not been achieved. Conventionally, they are realized based on the Faraday effect of magneto-optic materials under an external magnetic field; however, it has been challenging to integrate magneto-optic materials that are not compatible with complementary metal–oxide–semiconductors and that require bulky external magnet. Here we demonstrate a magnetic-free optical isolator based on aluminium nitride (AlN) piezoelectric modulators monolithically integrated on low-loss Si₃N₄ PICs. The transmission reciprocity is broken by spatio-temporal modulation of a Si₃N₄ microring resonator with three AlN bulk acoustic wave resonators that are driven with a rotational phase. This design creates an effective rotating acoustic wave that allows indirect interband transition in only one direction among a pair of strongly coupled optical modes. A maximum of 10 dB isolation is achieved under 300 mW total radiofrequency power applied to three actuators, with minimum insertion loss of 0.1 dB. An isolation bandwidth of 700 MHz is obtained, determined by the optical resonance linewidth. The isolation remains constant over nearly 30 dB dynamic range of optical input power, showing excellent optical linearity. Our integrated, linear, magnetic-free, electrically driven optical isolator could be a key building block for integrated lasers and optical interfaces for superconducting circuits.

集成光子学可使用光子集成电路 (PIC) 实现信号合成、调制和转换。已经开发了许多材料，其中氮化硅 (Si ₃ N ₄ ) 已成为主要平台，特别是用于非线性光子学。低损耗 Si ₃ N ₄ PIC 已广泛用于频率梳生成、窄线宽激光器、微波光子学和光子计算网络。然而，在所有已证明的 Si ₃ N _{4 功能中}集成光子学、光学非互易器件如隔离器和环行器尚未实现。传统上，它们是基于磁光材料在外磁场作用下的法拉第效应实现的；然而，集成与互补金属氧化物半导体不兼容且需要庞大的外部磁体的磁光材料一直具有挑战性。_{在这里，我们展示了一种基于单片集成在低损耗 Si 3} N ₄ PIC上的氮化铝 (AlN) 压电调制器的无磁光隔离器。_{Si 3} N ₄的时空调制破坏了传输互易性具有三个由旋转相位驱动的 AlN 体声波谐振器的微环谐振器。这种设计产生了一种有效的旋转声波，它允许在一对强耦合光学模式之间仅在一个方向上进行间接带间转换。在施加到三个执行器的 300 mW 总射频功率下，最大 10 dB 的隔离度可实现，最小插入损耗为 0.1 dB。获得 700 MHz 的隔离带宽，由光学谐振线宽决定。隔离在近 30 dB 的光输入功率动态范围内保持恒定，显示出出色的光学线性度。我们的集成、线性、无磁、电驱动光隔离器可以成为集成激光器和超导电路光接口的关键组成部分。