Multi-Junction VCSEL Array
Lumentum multi-junction VCSEL arrays can reach extremely high peak power, in the hundreds of watts, when driven with short, nanosecond pulses at low duty-factors (<1%), making them ideal for short, medium, and long-range LiDAR systems.
The multi-junctions in these VCSEL chips reduce the drive current required for emitting multiple photons for each electron. Optical power above 4 W per ampere is common. The emitters are compactly arranged to permit not just high power, but also high power density. Lumentum has demonstrated over 1 kW per square mm of die area at 125°C at 0.1% duty cycle.
For short distances, the VCSEL chip may be paired with a diffuser to illuminate a wide field of view. In this case, the higher power density reduces the chip area required. For longer distances, higher power in a smaller area eases the LiDAR optical design so there can be more power collimated into lower divergence beams which can then scan the scene.
VCSELs are more advantageous than multi-junction edge emitting lasers for LiDAR because of their narrower wavelength range over temperature and because they can be formed into addressable arrays of stripes or even a matrix-addressable format. Addressability permits replacement of mechanical LiDAR scanning with more robust, all-electronic LiDAR scanning.
Lumentum leverages its proven high-volume VCSEL manufacturing platform for mobile products to produce VCSEL arrays for the automotive market. Thus, high peak power can be offered at high volume and high quality.
Schematic of one emitter in a multi-junction VCSEL array