Abstract
Silicon photonics is an enabling technology that provides integrated photonic devices and systems with low-cost mass manufacturing capability. It has attracted increasing attention in both academia and industry in recent years, not only for its applications in communications, but also in sensing. One important issue of silicon photonics that comes with its high integration density is an interface between its high-performance integrated waveguide devices and optical fibers or free-space optics. Surface grating coupler is a preferred candidate that provides flexibility for circuit design and reduces effort for both fabrication and alignment. In the past decades, considerable research efforts have been made on in-plane grating couplers to address their insufficiency in coupling efficiency, wavelength sensitivity and polarization sensitivity compared with out-of-plane edge-coupling. Apart from improved performances, new functionalities are also on the horizon for grating couplers. In this paper, we review the current research progresses made on grating couplers, starting from their fundamental theories and concepts. Then, we conclude various methods to improve their performance, including coupling efficiency, polarization and wavelength sensitivity. Finally, we discuss some emerging research topics on grating couplers, as well as practical issues such as testing, packaging and promising applications.
Highlights
Integrated photonics is a promising solution to provide low-cost and high-performance photonic devices and systems, while complementary metal oxide semiconductor (CMOS) compatible silicon photonics such as silicon-on-insulator (SOI) platform has emerged as one of the most important technology for generation on-chip optical interconnects [1,2,3,4]
Since the first grating line span on y-axis d0 should be comparable to mode field diameter (MFD), footprint for a focusing grating couplers (GCs) can be further reduced by choosing a larger sector angle αs
Efficient coupling is an important aspect of silicon photonics
Summary
Integrated photonics is a promising solution to provide low-cost and high-performance photonic devices and systems, while complementary metal oxide semiconductor (CMOS) compatible silicon photonics such as silicon-on-insulator (SOI) platform has emerged as one of the most important technology for generation on-chip optical interconnects [1,2,3,4]. There are many high-performance optical components already available on SOI, one key challenge encountered by silicon photonic chip is to couple light to and from optical fibers efficiently. Efficient coupling from SMF to waveguide with size of hundreds of nanometers is a challenge due to the large modal size mismatch This problem is usually addressed using two solutions, in-plane (butt) edge coupling and off-plane (vertical) grating coupling [11,12,13]. Edge couplers usually consist of an inverse tapered waveguide, which means the width of waveguide is gradually decreasing along the propagation of light to the edge [14] As it gradually decreases, light confinement is reduced and the mode size becomes larger to be comparable with fiber mode. Practical issues concerning testing, packaging and applications of GC are provided
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
