倾斜耦合的光栅耦合器研究进展

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.