Broadband optical isolators and circulators are highly desirable for wavelength-division multiplexing, light detection, and ranging systems. However, the silicon-integrated optical isolators and circulators reported so far have a limited isolation bandwidth of only several nanometers, due to waveguide and material dispersion. In this paper, we report the development of broadband magneto-optical isolators on silicon nitride waveguides. We proposed a general method of dispersion compensation to achieve a constant phase difference between reciprocal and nonreciprocal phase shifts in a Mach–Zehnder interferometer over a wide frequency range. This method enabled a theoretical 30 dB isolation/circulation bandwidth of more than 240 nm, which covers the S, C, L, and U bands. The fabricated devices showed a maximum isolation ratio of 28 dB, crosstalk of −28dB${-}{28}\;{\rm dB}$, high 20-dB isolation bandwidth of 29 nm (3.48 THz), and a relatively low loss of 2.7 dB in the wavelength range of 1520–1610 nm. By further heating the reciprocal phase shifter based on the thermo-optic effect, the experimental 20 dB isolation bandwidth of the device increased to 90 nm (11.03 THz). This method has also been applied to the design of broadband, low-loss isolators, and O/C dual-band isolators/circulators. Our work experimentally demonstrated broadband-integrated optical isolators and circulators on silicon, paving the way for their use in optical communication, data communication, and LiDAR applications.

中文翻译：

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氮化硅光子平台上的超宽带磁光隔离器和循环器

宽带光学隔离器和循环器非常适合波分复用、光检测和测距系统。然而，由于波导和材料色散，迄今为止报道的硅集成光隔离器和环行器的隔离带宽有限，仅为几纳米。在本文中，我们报告了氮化硅波导上宽带磁光隔离器的开发。我们提出了一种色散补偿的通用方法，以在马赫-曾德尔干涉仪中在很宽的频率范围内实现互易和非互易相移之间的恒定相位差。该方法实现了理论 30 dB 隔离/超过 240 nm 的循环带宽，涵盖 S、C、L 和 U 频段。所制造的器件的最大隔离比为 28 dB，串扰为− 28dB${-}{28}\;{\rm dB}$，29 nm (3.48 THz) 的高 20 dB 隔离带宽，以及在 1520–1610 nm 波长范围内相对较低的 2.7 dB 损耗。通过进一步加热基于热光效应的互易移相器，该器件的实验20 dB隔离带宽提高到90 nm（11.03 THz）。该方法也已应用于宽带、低损耗隔离器和O/C双频隔​​离器/环行器的设计。我们的工作通过实验证明了硅上的宽带集成光隔离器和循环器，为它们在光通信、数据通信和激光雷达应用中的使用铺平了道路。