Optical all-pass filters, which exhibit constant amplitude response and pure phase variation, are extremely desired when only optical phase manipulation is required. However, many reported all-pass filters are accompanied by amplitude variations, which could degrade their performance. In this study, an all-pass filter is designed with constant amplitude and pure phase variation based on the analysis of the microring resonator response in the complex plane. The all-pass filter makes use of optical interference between the outputs of an all-pass microring resonator and a straight waveguide. Based on a silicon-on-insulator wafer, the all-pass filter is fabricated and its application to a microwave photonic phase shifter is also investigated. The all-pass filter exhibits a maximal magnitude variation of approximately 1.2 dB and a phase shift of 1.97π and can be continuously and widely tuned. This work offers a new approach to manipulate pure optical phases to improve the performance of optical devices and systems.

中文翻译：

---

绝缘硅上的光学全通滤波器

当只需要光学相位控制时，就非常需要表现出恒定幅度响应和纯相位变化的光学全通滤波器。但是，许多报道的全通滤波器都伴随有幅度变化，这可能会降低其性能。在这项研究中，基于对复杂平面中微环谐振器响应的分析，设计了具有恒定幅度和纯相位变化的全通滤波器。全通滤波器利用了全通微环谐振器和直波导的输出之间的光学干涉。基于绝缘体上硅晶片，制造了全通滤波器，并研究了其在微波光子移相器中的应用。全通滤波器的最大幅度变化约为1.2 dB，相移为1。97π，并且可以连续广泛地调谐。这项工作提供了一种操纵纯光学相位以改善光学设备和系统性能的新方法。