The first three-dimensional lidar sensor was introduced by Velodyne more than a decade ago. The spinning unit cost around $75,000 and was significantly larger than a smartphone. Apple needed to make lidar sensors radically cheaper and smaller in order to put one in each iPhone, and VCSELs helped the company do it.
What's a VCSEL? If you're building a laser using conventional semiconductor fabrication techniques, you have two basic options. You can make a laser that transmits light out the side of the wafer (known as an edge-emitting laser) or from the top (a vertical cavity surface emitting laser, or VCSEL).
Traditionally, edge-emitting lasers have been more powerful. VCSELs have been used for decades in everything from optical mice to optical networking gear. They were traditionally considered unsuitable for high-end applications where a lot of light was needed, but VCSELs have become more powerful as the technology has matured.
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