High-power compact VCSEL subsystem as game-changer for photoacoustic medical imaging and sensing

We review today's photonic systems (LD/LED/VCSEL/SSL) used for photoacoustic imaging and identify the major challenges to propel this technology into routine clinical use: a factor of 100 in cost, volume, and power consumption for photon generation must be reached. The photonic subsystem presented is based on a compact set-up of triple-junction 940nm and single-junction 850nm VCSEL arrays combined with bare ToF CMOS driver chips. We discuss the optomechanical set-up, the measured key parameters of individual VCSEL arrays and the manufactured VCSEL subsystem with 3.5kW optical peak power for pulse lengths from 10 to 100ns. Even at these high output powers, laser class 1 operation can be achieved. The integrated drivers from automotive LiDAR operate the VCSEL subsystem with a wall-plug efficiency of 25% at a repetition rate of 1kHz. The heat dissipation can be buffered in a small copper block, so the subsystem can directly be mounted within a medical handheld device with no active cooling. We discuss the target applications oxygenation and muscle perfusion for photoacoustic imaging using a combination of 760/800/850nm VCSEL arrays. This VCSEL-based subsystem can replace current photonic systems and is the game-changer for routine clinical use. In addition, the concept is scalable and paves the way towards future patch and sensor photoacoustic applications.