Abstract. We achieved considerable laser diode (LD) improvement after annealing InGaP/ InAlGaP laser structure at 950°C for a total annealing time of 2 min. The photoluminescence intensity is increased by 10 folds and full-wave at half-maximum is reduced from ∼30 to 20 nm. The measured LDs exhibited significantly reduced threshold current (I th ), from 2 to 1.5 A for a 1-mm long LD, improved internal efficiency (η i ), from 63% to 68%, and increased internal losses α i , from 14.3 to 18.6 cm −1 . Our work suggests that the use of strain-induced quantum well intermixing is a viable solution for high-efficiency AlGaInP devices at shorter wavelengths. The advent of laser-based solid-state lighting (SSL) and visible-light communications (VLC) highlighted the importance of the current findings, which are aimed at improving color quality and photodetector received power in SSL and VLC, respectively, via annealed red LDs. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.