High performance multijunction VCSELs

High power conversion efficiency (PCE) is one of the most distinctive features of semiconductor lasers, compared with other types of lasers. With the development of the reverse tunneling junction technology to form the cascaded multi-junction vertical cavity surface emitting lasers (VCSELs), a breakthrough is achieved in the performance of the power conversion efficiency. Moreover, some other specification performance is involved in more research works and product applications, such as the small divergence angle, wide range of operating temperature, high reliability, etc. In this paper, we report the research and product progress of multi-junction VCSELs in Everbright Photonics Ltd. By optimizing the structure design and the process of epitaxial growth and fabrication, the theoretical PCE value is simulated as high as 88% with 20 junctions VCSELs and the experimental PCE value is achieved as high as 74% with 15 junctions VCSELs. What’s more, by exploring the relationship between the divergence angle and the confinement factor of Oxidation Layers (OLs), we realize the divergence angle of 86% energy distribution as low as 13 degree. With the structure design of 6 cascaded tunneling junctions VCSELs product, the output power reduction ratio is less than 25% in the wide operating temperature range of -40°C to 125°C. Meanwhile, the reliability of high temperature operating lifetime (HTOL) is accumulated as high as 4000 hours under the condition of 5 nano-second pulse width and 125°C junction temperature, which is equivalent to about 400,000 hours of operating life-time for the module of LiDAR application.