Low Divergence Angle Output in Tunnel Junction Cascade Laser With in-Phase Mode Operation

In this study, we report a novel laser with in-phase super-mode coupled double emitter cascaded by tunnel junction. By incorporating a mode expansion layer on the P-type side of the upper emitter to suppress other high-order modes, pure in-phase fundamental mode operation demonstrated via far-field measurements and simulations is realized in the fast-axis direction with a slope efficiency of 2.08 W/A driven by
$100~\mu \text{s}$
, 100Hz quasi-continuous wave (QCW) bias current. More importantly, the only central peak of emitted in-phase mode has a low vertical far-field divergence angle of 12.69° due to the coupled design of the two adjacent emitters. The novel mode coupling structure has obvious benefits for the practical application of tunnel junction lasers in LIDAR detection areas.