High efficiency focusing double-etched SiN grating coupler for trapped ion qubit manipulation

A one-dimensional focusing grating coupler array based in silicon nitride (SiN) was proposed for trapped ion qubit manipulation. By applying inverse design optimization with a double-etched grating structure, a directionality of 98% was achieved. A small beam diameter of 2.5 mu m on the target ion with a low crosstalk of -36 dB was attained. Additionally, the impact of fabrication errors was investigated through a Monte Carlo simulation; within the accuracy of an electron beam lithography-based process, the output efficiency was maintained at 93%. (C) 2022 The Author(s). Published on behalf of The Japan Society of Applied Physics by IOP Publishing Ltd