Details

Autor(en) / Beteiligte

• Benedikovic, Daniel
• Alonso-Ramos, Carlos
• Guerber, Sylvain
• Le Roux, Xavier
• Cheben, Pavel
• Dupré, Cécilia
• Szelag, Bertrand
• Fowler, Daivid
• Cassan, Éric
• Marris-Morini, Delphine
• Baudot, Charles
• Boeuf, Frédéric
• Vivien, Laurent

Titel

Sub-decibel silicon grating couplers based on L-shaped waveguides and engineered subwavelength metamaterials

Ist Teil von

• Optics express, 2019-09, Vol.27 (18), p.26239-26250

Ort / Verlag

United States: Optical Society of America - OSA Publishing

Erscheinungsjahr

2019

Link zum Volltext

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• The availability of low-loss optical interfaces to couple light between standard optical fibers and high-index-contrast silicon waveguides is essential for the development of chip-integrated nanophotonics. Input and output couplers based on diffraction gratings are attractive coupling solutions. Advanced grating coupler designs, with Bragg or metal mirror underneath, low- and high-index overlays, and multi-level or multi-layer layouts, have proven less useful due to customized or complex fabrication, however. In this work, we propose a rather simpler in design of efficient off-chip fiber couplers that provide a simulated efficiency up to 95% (-0.25 dB) at a wavelength of 1.55 µm. These grating couplers are formed with an L-shaped waveguide profile and synthesized subwavelength grating metamaterials. This concept jointly provides sufficient degrees of freedom to simultaneously control the grating directionality and out-radiated field profile of the grating mode. The proposed chip-to-fiber couplers promote robust sub-decibel coupling of light, yet contain device dimensions (> 120 nm) compatible with standard lithographic technologies presently available in silicon nanophotonic foundries. Fabrication imperfections are also investigated. Dimensional offsets of ± 15 nm in shallow-etch depth and ± 10 nm in linewidth's and mask misalignments are tolerated for a 1-dB loss penalty. The proposed concept is meant to be universal, which is an essential prerequisite for developing reliable and low-cost optical couplers. We foresee that the work on L-shaped grating couplers with sub-decibel coupling efficiencies could also be a valuable direction for silicon chip interfacing in integrated nanophotonics.