Open AccessWafer-level testing of inverse-designed and adjoint-inspired vertical grating coupler designs compatible with DUV lithography
Author(s) -
Thomas Van Vaerenbergh,
Peng Sun,
Sean Hooten,
Mudit Jain,
Quentin Wilmart,
Ashkan Seyedi,
Zhihong Huang,
Marco Fiorentino,
Ray Beausoleil
Publication year - 2021
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.433744
Subject(s) - insertion loss , materials science , optics , grating , lithography , coupling loss , wafer , return loss , reflection loss , photonics , coupled mode theory , optoelectronics , optical fiber , refractive index , computer science , physics , telecommunications , composite number , antenna (radio) , composite material
Perfectly vertical grating couplers have various applications in optical I/O such as connector design, coupling to multicore optical fibers and multilayer silicon photonics. However, it is challenging to achieve perfectly vertical coupling without simultaneously increasing reflection. In this paper, we use the adjoint method as well as an adjoint-inspired methodology to design devices that can be fabricated using only a single-etch step in a c-Si 193 nm DUV immersion lithography process, while maintaining good coupling and low reflection. Wafer-level testing of devices fabricated by a pilot line foundry confirms that both design paradigms result in state-of-the-art experimental insertion loss (<2 dB) and bandwidths (∼20 nm) while having only moderate in-band reflection (<-10 dB). Our best design has a (median) 1.82 dB insertion loss and 21.3 nm 1 dB-bandwidth.