Visible wavelength silicon nitride focusing grating coupler with AlCu/TiN reflector

Dark field image of the fabricated focusing grating couplers with metal back-reflector.

Dark field image of the fabricated focusing grating couplers with metal back-reflector.

Abstract:
High performance silicon nitride focusing grating couplers with AlCu/TiN reflector for a visible wavelength (660 nm) have been designed and fabricated in a standard complementary metal-oxide-semiconductor (CMOS) pilot line. The influence of the bottom oxide cladding thickness on the grating decay length and efficiency is theoretically and experimentally investigated. It is shown how the metal reflector not only increases the efficiency but also allows reducing the radiated beam size. Coupling efficiencies above 59% have been measured for compact focusing gratings.
Sebastian Romero-García, Florian Merget, Frank Zhong, Hod Finkelstein, and Jeremy Witzens, “Visible wavelength silicon nitride focusing grating coupler with AlCu/TiN reflector,” Opt. Lett. 38, 2521-2523 (2013)
http://www.opticsinfobase.org/ol/abstract.cfm?URI=ol-38-14-2521