Single etch fibre-to-chip grating couplers for high-volume production in SOI

Fibre-to-chip grating couplers are an efficient means for injecting and extracting light from silicon-wire waveguides. Here we present the design of single-etch couplers, based on effective media implemented with sub-wavelength gratings. We show that the pitch of these sub-wavelength structures can be increased to make their fabrication compatible with deep-ultraviolet lithography, without compromising their effective medium behavior. We experimentally demonstrate fully-etched grating couplers fabricated with DUV lithography. \ua9 2011 IEEE.Peer reviewed: YesNRC publication: Ye

High efficiency blazed fiber-chip grating coupler with interleaved trenches

We demonstrate a fiber-chip surface grating coupler that interleaves standard full and shallow-etched trenches to maximize directionality in the upward direction. The coupler is implemented in a regular SOI substrate with 220 nm silicon thickness and etch depths of 220 nm (full etch) and 70 nm (shallow etch), as offered by silicon photonic foundries. The blazing effect is controlled by adjusting the separation between the two sets of trenches. This way, grating directionality exceeding 95% is achieved independently of the bottom oxide (BOX) thickness. Couplers have been fabricated at LETI using 193 nm DUV lithography on 200 mm SOI wafers with 2 \u3bcm BOX. The measured coupling efficiency is-2.1 dB with a 3 dB bandwidth of 52 nm.Peer reviewed: YesNRC publication: Ye