Thin-film-lithium-niobate (TFLN) photonics has attracted intensive attention and become very popular in recent years. Here, an ultra-compact TFLN on-chip dispersion compensator is proposed and realized to provide a promising solution for dispersion control. The proposed dispersion compensator is composed of chirped multimode waveguide gratings (CMWGs) arranged in zigzag-cascade, enabling high footprint compactness and scalability. Particularly, these CMWGs are circulator-free and very convenient for cascading, owing to the TE0–TE1 mode conversion and the assistance of the TE0–TE1 mode (de)multiplexer. The present configuration with CMWGs in zigzag-cascade also overcomes the drawback of being unable to use waveguide spirals for large-range time delay and dispersion control due to the TFLN’s anisotropy. In addition, positive/negative dispersion control is realized by appropriately choosing the input port of the CMWGs. In the experiment, 2-mm-long CMWGs are used to provide a dispersion value of about +1.5 ps/nm and −1.2 ps/nm over a 21-nm-wide bandwidth, and there are up to 32 CMWGs in cascade demonstrated experimentally, showing a maximal dispersion of 49.2 ps/nm and −39.3 ps/nm. The corresponding average propagation loss is as low as 0.47 dB/cm, and the fabricated chip with 32 CMWGs in zigzag-cascade has a footprint as compact as 0.16 × 4.65 mm2. Finally, the present on-chip dispersion compensator is used successfully to compensate for the dispersion originating from a 5-km-long singlemode fiber (SMF) and high-quality eye-diagrams are achieved for the recovered 40 Gbps OOK signals, showing great potential for optical systems such as high-speed interconnects in datacenters.

中文翻译：

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用于色散补偿的超紧凑薄膜铌酸锂光子芯片


近年来，薄膜铌酸锂 （TFLN） 光子学引起了广泛关注并变得非常流行。在这里，提出并实现了一种超紧凑的 TFLN 片上色散补偿器，为色散控制提供了一种有前途的解决方案。所提出的色散补偿器由以锯齿形级联排列的啁啾多模波导光栅 （CMWG） 组成，可实现高占地面积的紧凑性和可扩展性。特别是，由于 TE0-TE1 模式转换和 TE0-TE1 模式（解）复用器的帮助，这些 CMWG 是无环行器的，并且非常便于级联。目前 CMWG 呈锯齿形级联的配置也克服了由于 TFLN 的各向异性而无法使用波导螺旋进行大范围时间延迟和色散控制的缺点。此外，通过适当选择 CMWG 的输入端口，可实现正/负色散控制。在实验中，使用 2 mm 长的 CMWG 在 21 nm 宽带宽上提供约 +1.5 ps/nm 和 -1.2 ps/nm 的色散值，实验证明有多达 32 个 CMWG 级联，显示最大色散为 49.2 ps/nm 和 −39.3 ps/nm。相应的平均传播损耗低至 0.47 dB/cm，具有 32 个 CMWG 的锯齿形级联制造芯片的封装尺寸为 0.16 × 4.65 mm2。最后，目前的片上色散补偿器成功地用于补偿源自 5 km 长的单模光纤 （SMF） 的色散，并为恢复的 40 Gbps OOK 信号实现了高质量的眼图，显示出在光学系统（如数据中心高速互连）方面的巨大潜力。