Manipulation of coherent emission in multiaperture VCSEL arrays by laser patterning

Laterally coupled multi-aperture VCSELs provide a powerful platform for engineering transverse supermodes and tailoring emission properties beyond the limits of conventional single-aperture devices. In this work, we investigate mode control in oxide-confined coupled VCSEL structures using two complementary approaches: localized post-fabrication surface modification by femtosecond-laser ablation and electrically induced gain shaping. For two-aperture devices, shallow laser ablation applied to the top DBR of a single aperture enables selective suppression of the antisymmetric supermode and stabilization of symmetric single-mode emission with increased side-mode suppression. The resulting mode control leads to a side-mode suppression ratio exceeding 20 dB at 6 mA. In addition, self-injection-locking behavior in the coupled-cavity system is accompanied by a strong enhancement of the intrinsic frequency response beyond 100 GHz, highlighting the high-speed modulation potential of this approach. In extended arrays, engineered gain gradients in a ten-aperture device lead to controlled supermode localization and electrically driven beam steering. Furthermore, four-aperture coupled VCSELs are shown to exhibit robust coherent supermode formation with stable linear polarization, discrete supermode switching under asymmetric excitation, and directional emission control governed by the spatial symmetry of the electrically driven apertures. The presented results demonstrate that combined gain and loss engineering offers a flexible and scalable route toward high-speed, beam-controllable VCSEL arrays compatible with post-fabrication tuning and integrated photonic applications.