A Review of Silicon Photonics LiDAR

In the early 20th century, the reflection of electromagnetic waves emitted by ships from the metallic frame of other nearby ships was used as early collision warning system in poor visibility weather condition. In subsequent decades, the importance of detecting incoming bombers motivated the advancement of radio detection and ranging (radar) systems where the roundtrip time of a short pulse was used to find the target distance whereas the direction of the antenna was used to localize the target. Later advancements in phased array technology replaced the mechanically scanned antenna with electronically scanned versions enabling faster target localization, and ultimately, tracking multiple concurrent targets. Light detection and ranging (Iidar), initially referred to as laser radar, was developed shortly after the invention of lasers in the $1960\mathrm{s}$. The primary early applications were in metrology, military, and scientific discoveries and research. There has been a recent commercial interest in lidar for its potential application in advanced driver-assistance systems (ADAS) and self-driving cars.