Continuously apodized fiber-to-chip surface grating coupler with refractive index engineered subwavelength structure

Abstract

Continuously apodized fiber-to-chip surface grating coupler with refractive index engineered subwavelength structure Halir, R.; Cheben, P.; Schmid, J. H.; Ma, R.; Bedard, D.; Janz, S.; Xu, D.-X.; Densmore, A.; Lapointe, J.; Molina-Fernández, Í. We demonstrate a fully etched, continuously apodized fiber-to-chip surface grating coupler for the first time (to our knowledge). The device is fabricated in a single-etch step and operates with TM-polarized light, achieving a coupling efficiency of 3:7 dB and a 3 dB bandwidth of 60 nm. A subwavelength microstructure is employed to generate an effective medium engineered to vary the strength of the grating and thereby maximize coupling efficiency, while mitigating backreflections at the same time. Minimum feature size is 100 nm for compatibility with deep-UV 193 nm lithography.

Dielectric laser accelerators

“…30), experimental coupling efficiency of about 70 percent was demonstrated on the silicon-on-insulator platform (Sfar-Zaoui et al, 2012). With sub-wavelength microstructures the mode field overlap could reach 94 percent with minimal back reflection, and 43 percent coupling has been experimentally achieved (Halir et al, 2011).…”

Low-Loss Silicon Waveguides and Grating Couplers Fabricated Using Anisotropic Wet Etching Technique

“…The coupling efficiency of a grating coupler is decided by how well it directs light toward the optical fiber and how well the radiated field matches the Gaussian field profile of the fiber mode. Several grating coupler designs with high coupling efficiency have been previously proposed both using 1D line gratings (Taillaert et al, 2004;Cheben et al, 2006;Roelkens et al, 2008;Tang et al, 2010) and 2D subwavelength structures (Chen and Tsang, 2009;Halir et al, 2010).…”

Improving the efficiency of fibre-chip grating couplers near 1310 nm

“…We can further improve the coupling efficiency by apodizing the dual-etch grating to improve the mode matching efficiency with optical fibres [3,5]. In general, we want to keep all dimensions larger than 100 nm for the ease of fabrication and compatibility with DUV-193nm processing as it would typically be used in high volume production.…”