Grating couplers are the best solution for testing nano-photonic circuits. Their main benefit is that they allow access via an optical fiber from the top and therefore there is no need to dice the chip and prepare the facets crucially. In the PLATON project grating couplers were designed to couple TM mode into and out of the SOI waveguides. Simulations came up with a grating coupler layout capable of theoretical coupling losses lower than 3dB for 1550 nm in TM configuration. A fully etched grating structure was chosen for fabrication simplicity and the optimal filling factor was found. The structures were fabricated using proximity error correction (PEC) and show a uniform coupling efficiency for all couplers. Therefore they are well-suited for all applications which demand for stable fiber-to-chip coupling. The spectral response of the structures was measured from 1500 to 1580 nm with 2 nm step and measuring the fiber-tofiber losses of three straight waveguides equipped with three grating couplers with different gap widths. The optimal grating period exhibits adequate coupling losses of 3.23 dB per coupler at 1557 nm, being therefore the most promising design.

Date Published: 10 May 2012
PDF: 8 pages
Proc. SPIE 8431, Silicon Photonics and Photonic Integrated Circuits III, 84310G (10 May 2012); doi: 10.1117/12.922846

Published in SPIE Proceedings Vol. 8431:
Silicon Photonics and Photonic Integrated Circuits III
Laurent Vivien; Seppo K. Honkanen; Lorenzo Pavesi; Stefano Pelli, Editor(s)