Inverse Designed Couplers for Use in Gallium Arsenide Photonics

Highly efficient photonic couplers are a necessary component of a scalable platform to couple quantum emitters into quantum fiber networks. We inverse-designed couplers for use in gallium arsenide membrane-based photonics that are compatible with indium arsenide quantum dots, one of the highest quality quantum light sources available. We fabricated and tested at least 4 instances of devices following 11 different designs. All inverse-designed structures outperformed the traditional grating outcoupler in a single-mode optical fiber optical setup. Using a novel sleeve and bulk fabrication method allowed for a smaller allowable minimum feature size constraint in the inverse design optimization protocol. Employing this new design constraint improved the average device transmission efficiency from 17.4% to 27.5%. The use of broadband optimization criteria did not result in statically significant improvement in actual bandwidth, but did decrease the variance in the measured bandwidth, suggesting a more robust design.