Ultracompact Fiber-to-Chip Metamaterial Edge Coupler

Compact fiber-to-chip light coupling with low loss and large bandwidth, SMF-to-chip edge coupler in particular, is extensively demanded in integrated photonics. The inescapable challenge of edge coupler is the difficulty and complexity in fabrication and packaging. During the past decades, metamaterials have manifested marvelous talent in integrated photonics. Here, we experimentally demonstrate an ultracompact edge coupler via metamaterial for SMF with a mode field diameter of 10 μm, which is fully based on silicon-on-insulator material and a CMOS compatible fabrication process. In this work, we theoretically analyze the coupling performance and the fabrication difficulty. The experimental results show that this metamaterial-based coupler possesses low coupling loss and broad bandwidth simultaneously with the coupling length of only 90 μm. At 1550 nm, the coupling losses are 2.22/2.53 dB/facet for the fundamental TE/TM mode, while the minimum average loss could reach 1.81 dB/facet. The measured bandwidth with a loss below 3 dB is as broad as 120 nm, covering the entire C/L band. Moreover, this prominently eased fabrication process potentially exhibits significant superiority in both research and industrial applications.