倾斜耦合的光栅耦合器研究进展

近年来，片上光子集成技术备受关注并飞速发展，但在光纤与芯片、芯片与芯片上实现高效、高可靠性的光耦合仍是难题。光栅因其制作简单，位置灵活，对准容差大及可实现片上测试等一系列优点而备受研究者的关注。目前在绝缘体上硅(SOI)平台和绝缘体上铌酸锂(LNOI)平台上已开发出大量的光栅耦合器件，并获得较高的耦合效率和大带宽。该文主要介绍光栅耦合器的工作原理和主要性能指标，阐述了均匀光栅、倾斜光栅、闪耀光栅和切趾光栅耦合的特点及现阶段进展，并对具有代表性的一维光栅性能指标进行了比较。结果表明，分布式布喇格反射镜和金属反射镜可有效地提升光栅耦合效率。此外，该文还介绍了基于LNOI平台的几种光栅耦合器，其可帮助研究者们梳理光栅耦合器的发展历程、研究现状及各耦合器的特点，为未来研究提供一定的参考。

Recent Advances in Tilt-Coupled Grating Couplers

In recent years, on-chip photonic integration technology has received extensive attention and developed rapidly. However, it is still challenging to achieve optical coupling between optical fiber and chip, and between chip and chip with high efficiency and high reliability. The gratings, possessing many advantages such as easy fabrication, flexible position, large alignment tolerance, and available on-chip testing, have attracted broad interest. Recently, a large number of grating coupling devices have been developed on the silicon-on-insulator(SOI) platform and lithium niobate on insulator(LNOI) platform with high coupling efficiency and large bandwidth. This paper mainly introduces the working principle and main performance specifications of grating couplers. The coupling characteristics and current progress of uniform grating, slanted grating, blazed grating and apodized grating, are described. By comparing the performance of recent works on one-dimensional gratings, it is found that the Bragg mirrors and metal mirrors can improve the grating coupling efficiency. In addition, several LNOI-based grating couplers are also introduced. By combing the development history and state-of-the-art of grating couplers, it is hope that this review could provide useful guidance for future research on grating coupler.