In this paper, we report a low-loss photonic integrated circuits (PICs) platform at blue wavelengths of the visible spectral regime. Silicon nitride (SiN) is a popular passive waveguide material due to its fabrication flexibility, CMOS compatibility and spectral transparency in this wavelength regime. For active devices including lasers, gallium nitride (GaN) and its alloys are considered. Several basic building blocks for the development of a complete integrated platform, including blue diode lasers, in-plane- and out-of-plane light couplers, as well as on-and off-chip coupling between these active and passive components are theoretically investigated. The proposed in-plane and out-of-plane architectures operate through edge- and vertical grating couplers (VGCs), respectively. With edge-coupling, large mode-mismatch between the GaN laser diode and SiN waveguide is alleviated through nanotapers on both the active and passive sections and the calculated peak coupling efficiency is achieved to be 74% at a wavelength of 450 nm. We also separately designed efficient VGCs for coupling light from standard, commercial, off-the-shelf fibers to the SiN chip, and edge couplers for fiber-chip coupling, exhibiting coupling efficiencies of 51% and 83%, respectively. For robust on-chip light-coupling between active and passive circuit elements, with relaxed alignment tolerances, two approaches, i.e., flip-chip based hybrid integration and evanescent coupling based heterogeneous integration are studied. Calculated maximum coupling efficiencies of 40% (−4 dB) are achieved for both the hybrid and heterogeneous schemes. The theoretical work performed is an initial step towards demonstrating complex blue PICs which could offer a comprehensive range of photonic functionalities.

中文翻译：

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用于蓝光波长的 III-N/Si3N4 集成光子学平台

在本文中，我们报告了可见光谱区蓝色波长的低损耗光子集成电路 (PIC) 平台。氮化硅 (SiN) 是一种流行的无源波导材料，因为它在该波长范围内具有制造灵活性、CMOS 兼容性和光谱透明度。对于包括激光器在内的有源器件，可以考虑氮化镓 (GaN) 及其合金。从理论上研究了开发完整集成平台的几个基本构建块，包括蓝色二极管激光器、面内和面外光耦合器，以及这些有源和无源组件之间的片上和片外耦合. 所提出的面内和面外架构分别通过边缘和垂直光栅耦合器 (VGC) 运行。通过边缘耦合，GaN 激光二极管和 SiN 波导之间的大模式失配通过有源和无源部分的纳米锥得到缓解，并且计算出的峰值耦合效率在 450 nm 波长处达到 74%。我们还分别设计了用于将来自标准、商用、现成光纤的光耦合到 SiN 芯片的高效 VGC，以及用于光纤芯片耦合的边缘耦合器，耦合效率分别为 51% 和 83%。为了在有源和无源电路元件之间实现稳健的片上光耦合，在放宽对准公差的情况下，研究了两种方法，即基于倒装芯片的混合集成和基于渐逝耦合的异构集成。对于混合和异构方案，计算出的最大耦合效率为 40% (-4 dB)。