On-chip spectrometers offer great opportunity for developing wearable monitoring devices, industrial remote sensing systems, and agricultural evaluation. In practical application scenarios, the spectrometer is imperative to be highly integrated and capable of processing light signals with randomly polarized states in the environment. Here, we propose and demonstrate a monolithically integrated silicon photonic spectrometer with a compact footprint of 0.24 × 1.0 mm² for arbitrarily polarized light for the first time. The spectrometer couples the light with uncertain polarization states to the TE₀ modes guided in two separated waveguides using a polarization splitter rotator. These two TE₀ modes are then filtered and received with a very concise configuration by utilizing the unique bidirectionality of a tunable adiabatic elliptical-microring with the maximized free spectral range and a monolithically integrated Ge/Si photodetector (PD). Measurement results show the present spectrometer achieves a broad operation window of 36.5 nm as well as a high resolution of 0.2 nm. The lowest detectable power is characterized experimentally, demonstrating the capability to detect the spectra with a low peak power of −55 dBm and distinguish a peak power difference as high as 45 dB with the integrated Ge/Si PD. As a result, the broadband complex spectra reconstruction with arbitrary polarization states demonstrates our spectrometer is featuring monolithic integration and polarization-insensitive operation.

中文翻译：

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用于任意偏振光的单片集成硅光子能谱器


片上光谱仪为开发可穿戴监测设备、工业遥感系统和农业评估提供了绝佳的机会。在实际应用场景中，光谱仪必须高度集成，并能够处理环境中具有随机偏振状态的光信号。在这里，我们提出并演示了一种单片集成的硅光子光谱仪，该光谱仪首次用于任意偏振光，其占地面积仅为 0.24 × 1.0 mm²。光谱仪使用偏振分流器旋转器将偏振状态不确定的光耦合到两个分离波导中引导的 TE₀ 模式。然后，通过利用具有最大自由光谱范围的可调谐绝热椭圆微环和单片集成 Ge/Si 光电探测器 （PD） 的独特双向性，以非常简洁的配置对这两种 TE₀ 模式进行过滤和接收。测量结果表明，该光谱仪实现了 36.5 nm 的宽工作窗口以及 0.2 nm 的高分辨率。实验表征了最低的可检测功率，证明了能够检测具有 −55 dBm 低峰值功率的光谱，并能够区分高达 45 dB 的峰值功率差。因此，具有任意偏振态的宽带复数光谱重建表明，我们的光谱仪具有单片集成和偏振不敏感操作的特点。