The optical all-pass filter (APF), which exhibits a constant amplitude response and a variable phase response, is a key to manipulating the optical phase without inducing signal amplitude distortion. High-order APFs are significantly demanded because they can afford large time delays and phase shifts. However, to date, only first-order APFs based on lossy waveguides have been reported. Although high-order APFs can be simply obtained by cascading multiple first-order APFs, the complexity and size are increased. To solve this problem, we propose and demonstrate a second-order APF using Mach–Zehnder interferometer-assisted microring resonators. The device is fabricated based on a silicon-on-insulator platform. Based on the second-order APF, an adjustable time delay between 553 and 948 ps is obtained, and the corresponding amplitude variation is less than 1.7 dB. Meanwhile, a microwave photonic phase shifter is also obtained based on the APF. The microwave phase shift can be adjusted from 0 to 3.27π, with an RF power variation within 2.4 dB. Additionally, the second-order APF can be reconfigured to a first-order APF, which significantly enhances its flexibility. The reconfigured first-order APF can realize an adjustable time delay between 257 and 429 ps, and the amplitude variation is less than 0.9 dB. The proposed high-order APF provides a novel approach to manipulating optical signals.

中文翻译：

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可重构二阶光学全通滤波器

具有恒定幅度响应和可变相位响应的光学全通滤波器 (APF) 是在不引起信号幅度失真的情况下操纵光学相位的关键。高阶 APF 的需求很大，因为它们可以承受较大的时间延迟和相移。然而，迄今为止，仅报道了基于有损波导的一阶 APF。虽然通过级联多个一阶APF可以简单地获得高阶APF，但是增加了复杂度和尺寸。为了解决这个问题，我们提出并演示了使用 Mach-Zehnder 干涉仪辅助微环谐振器的二阶 APF。该器件基于绝缘体上硅平台制造。基于二阶 APF，可获得 553 到 948 ps 之间的可调时间延迟，相应的幅度变化小于1.7 dB。同时，基于APF也得到了微波光子移相器。微波相移可在 0 至 3.27 范围内调节π，射频功率变化在 2.4 dB 以内。此外，二阶 APF 可以重新配置为一阶 APF，这显着增强了其灵活性。重构后的一阶APF可实现257~429 ps的可调时延，幅度变化小于0.9 dB。所提出的高阶 APF 提供了一种操纵光信号的新方法。