Perfectly vertical surface grating couplers using subwavelength engineering for increased feature sizes

• DOI: 10.1364/ol.395292
• Publication Date: 2020-05-18T11:30:27Z
• Authors: Mohsen Kamandar D...; Yuri Grinberg; Daniele Melati; Pavel Cheben; Jens H. Schmid; Alejandro Sánchez...; Alejandro Ortega-...; Gonzalo Wangüemer...; Ross Cheriton; Siegfried Janz; Dan-Xia Xu
• Keywords: Silicon photonics; 621; diffraction gratings; Optoelectrónica; grating couplers; coupling efficiency; 01 natural sciences; 620; Subwavelength grating metamaterials; effective medium theory; 0103 physical sciences; subwavelength gratings; Fotónica; space division multiplexing; Surface grating couplers; Óptica

We present perfectly vertical grating couplers for the 220 nm silicon-on-insulator platform incorporating subwavelength metamaterials to increase the minimum feature sizes and achieve broadband low back-reflection. Our study reveals that devices with high coupling efficiencies are distributed over a wide region of the design space with varied back-reflections, while still maintaining minimum feature sizes larger than 100 nm and even 130 nm. Using 3D-finite-difference time-domain simulations, we demonstrate devices with broadband low back-reflection of less than

−

20

d B

over more than 100 nm bandwidth centered around the C-band. Coupling efficiencies of 72% and 67% are achieved for minimum feature sizes of 106 nm and 130 nm, respectively. These gratings are also more fabrication tolerant compared to similar designs not using metamaterials.