Near infrared (NIR) wavelengths are a popular choice for optical sensing, because infrared lasers are safer for human vision than visible lasers operating at similar output power. Operating a laser at higher power can extend the object detection range for remote sensing applications.
Visible laser diodes can be used for sensing if operated at low power or limited to low-risk environments; underwater sensing is an example. LWIR wavelengths are produced by quantum cascade lasers (QCLs), which are useful for detecting numerous chemical signatures and are also an emerging 3D sensor technology. QCLs are rare and exotic lasers: their system architecture differs significantly from standard laser diodes. Consequently, QCLs are more expensive than the devices discussed above.
Depth sensors in consumer electronics
The rise of vertical-cavity surface-emitting lasers (VCSELs) for 3D sensing in consumer electronics is a particularly important technology trend. Applications of disruptive VCSEL technology include mobile devices, game consoles, augmented and virtual reality (AR/VR), and home entertainment systems. Optical elements can shape the light from an infrared source into a pattern (structured light) or sheet of illumination, and measuring the light reflected from objects provides depth information. Compared to edge-emitter laser diodes, VCSELs can produce more accurate data due to their superior beam quality and wavelength stability, and the single emitters are easily scaled into mass-producible 2D arrays. Apple (USA) adopted VCSEL-based 3D sensor technology for the TrueDepth camera in iPhone X smartphones.