Optical isolators, while commonplace in bulk- and fiber-optic systems, remain a key missing component in integrated photonic systems. Isolation using magneto-optic effects has been difficult to implement due to fabrication restraints, motivating use of other non-reciprocal effects such as temporal modulation. We demonstrate a non-reciprocal modulator comprising a pair of microring modulators and a microring phase shifter in an active silicon photonic process which, in combination with standard frequency filters, facilitates isolation. Isolation up to 13 dB is measured with a 3 dB bandwidth of 2 GHz and insertion loss of 18 dB. As one potential application is cross-talk suppression in bi-directional communication links, we also show transmission of a 4 Gbps data signal through the isolator while retaining a wide-open eye diagram. This compact design, in combination with increased modulation efficiency, could enable modulator-based isolators to become a standard `black-box' component in integrated photonics foundry platform component library.
DC-to-GHz Modulation In Microring Modulators Using Ferroelectric Nematic Liquid Crystal-on-Silicon in a Foundry Photonic Process
University of British Columbia（不列颠哥伦比亚大学）；Dream Photonics Inc.（梦光子有限公司）；Polaris Electro-Optics（波利斯光电）；Quantum Matter Institute, University of British Columbia（不列颠哥伦比亚大学量子物质研究所）
集成光子学使得能够使用光子集成电路（PIC）进行信号合成、调制和转换。已经开发了许多材料，其中氮化硅（Si $_3$ N $_4$）已经成为特别是用于非线性光子学的领先平台。低损耗Si $_3$ N $_4$ PIC已广泛用于频率梳产生、窄线宽激光器、微波光子学、光子计算网络，甚至表面电极离子阱。然而，在Si $_3$ N $_4$集成光子学的所有已展示功能中，尚未实现光学非互易装置，例如隔离器和循环器。传统上，它们是基于磁光材料在外部磁场下的法拉第效应来实现的。然而，集成不与CMOS兼容并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，我们展示了一个无磁光隔离器的基础上氮化铝（AlN）压电调制器单片集成在超低损耗硅$_3$ N $_4$ PIC。透射互易性通过Si $_3$ N $_4$微谐振器与三个AlN体声波谐振器的时空调制被打破，所述三个AlN体声波谐振器用旋转相位驱动。这种设计产生了一种有效的旋转声波，允许在一对强耦合的光学模式之间仅在一个方向上进行间接带间跃迁。在施加到每个致动器的100 mW RF功率下实现最大10 dB隔离，最小插入损耗为0.1 dB。隔离度在近30 dB的光输入功率动态范围内保持恒定，表现出出色的光学线性。我们的集成、线性、无磁、电驱动光学隔离器可以成为集成激光器、芯片级LiDAR引擎以及超导电路光学接口的关键构建模块。
