Fabrication-Tolerant Single-Transverse-Mode Supersymmetric Laser Arrays

Abstract

The semiconductor supersymmetric (SUSY) laser arrays have achieved single-transverse-mode operation with high output powers, which hold great potential for integrated optoelectronic devices for optical communication and ranging systems. However, the single-transverse-mode characteristics may deteriorate rapidly when the ridge waveguide width varies due to fabrication error. In this work, fabrication-tolerant single-transverse-mode SUSY laser arrays are designed using robust direct search (RDS) under the odd/even supermode double-sided coupling scheme. Two independent superpartners are introduced on both sides of the main array, with one coupling and eliminating the higher-order odd symmetry supermodes, and the other coupling and eliminating the higher-order even symmetry supermodes in the main array, enabling more efficient coupling of higher-order transverse modes into the lossy superpartners, which leads to the increased loss of high-order supermodes. RDS design method is used to improve the single-transverse-mode characteristics with fabrication tolerance, which considers the fabrication error in ridge waveguide width during the optimization process. The mode discrimination, defined as the difference between the modal gain of fundamental supermode and the highest modal gain among higher-order supermodes, is calculated to evaluate the transverse mode characteristics. Larger mode discrimination corresponds to better single-transverse-mode characteristics. We demonstrate odd/even supermode double-sided coupling SUSY laser arrays composed of five, seven and nine-ridge main array using the RDS, achieving average mode discrimination within ±0.1 μm ridge width variations of 36.61 GHz, 36.27 GHz, and 35.41 GHz, respectively, when the maximum mode discrimination is 50 GHz. Compared to conventional design method, the average mode discrimination increases by 8.21 GHz, 7.18 GHz, and 5.66 GHz, proving better single-transverse-mode characteristics with fabrication tolerance. The proposed fabrication-tolerant single-transverse-mode SUSY laser arrays could find potential applications in integrated optoelectronic devices for optical communication and ranging systems.