Photonic-integrated circuits based on erbium-doped thin film lithium niobate on insulator has attracted broad interests with insofar various waveguide amplifiers and microlasers demonstrated. Wideband operation facilitated by the broadband absorption and emission of erbium ions necessitates the functional integration of wavelength filter and multiplexer on the same chip. Here, a low-loss wavelength division multiplexer at the resonant pumping and emission wavelengths (∼1480 nm and 1530–1560 nm) of erbium ions based on angled multimode interferometer is realized in the erbium-doped thin film lithium niobate on insulator fabricated by the photolithography assisted chemomechanical etching technique. The minimum on-chip insertion losses of the fabricated device are <0.7 dB for both wavelength ranges, and a 3-dB bandwidth of >20 nm is measured at the telecom C-band. Besides, direct visualization of the multimode interference pattern by the visible upconversion fluorescence of erbium ions compares well with the simulated light propagation in the multimode interferometer. Spectral tuning of the wavelength division multiplexer by structural design is also demonstrated and discussed.

中文翻译：

---

采用在绝缘体上掺铒薄膜铌酸锂上制造的倾斜多模干涉仪进行片上波分复用

基于绝缘体上掺铒薄膜铌酸锂的光子集成电路已经引起了广泛的兴趣，目前已展示了各种波导放大器和微型激光器。铒离子的宽带吸收和发射促进了宽带操作，因此需要将波长滤波器和多路复用器功能集成在同一芯片上。这里，在绝缘体上的掺铒薄膜铌酸锂中实现了基于成角度多模干涉仪的铒离子谐振泵浦和发射波长（~1480 nm和1530-1560 nm）的低损耗波分复用器。光刻辅助化学机械蚀刻技术。所制造器件的最小片上插入损耗在两个波长范围内均 <0.7 dB，并且在电信 C 波段测量到 >20 nm 的 3 dB 带宽。此外，通过铒离子的可见上转换荧光直接可视化多模干涉图案与多模干涉仪中的模拟光传播进行了很好的比较。还演示并讨论了通过结构设计对波分复用器进行光谱调谐。