Very compact multi-junction VCSEL arrays

LUMENTUM's short pulse single-junction VCSEL arrays are currently being deployed in Time of Flight (ToF) sensors for short-range Light Detection and Ranging (LIDAR) applications in consumer electronics. However, single-junction VCSEL devices have a slope efficiency (SE) of only around 1.1 W/A making them unsuitable for longer range or higher power applications. With the increasing demand of LIDAR in both automotive and non-automotive applications, there is a need for ultra-short pulse, high peak power VCSELs. Multi-junction VCSELs are ideal candidates for this segment. The multi-junction VCSEL consists of stacked gain regions connected by highly doped tunnel junctions. An electron which radiatively recombines with a hole in one gain region, generating a photon, can tunnel into the conduction band of the next gain region, via the highly doped region, and is available to generate another photon, and so on. The total photons or output power scales with the number of junctions in the device. The optical power density and chip size are critical parameters of a LIDAR module. In this paper, we report the results of compact multi-junction arrays capable of delivering very high peak power. A five junction 905nm VCSEL array of die size 0.5mm x 0.3mm and a peak optical power of 26.5W, corresponding to power density of 100 kW/cm(2), at 6.0A, and nanosecond pulses is reported. These results pave the way to very compact and powerful illuminators for line scanning, in robotics, industrial, and Internet of Things (IoT) applications.