Optimizing performance of a pulsed laser diode driver based on a GaN FET

Lidar optical time-of-flight distance measurement has become a primary method to make distance measurements of remote targets. Lidar applications such as 3-D continuous mapping for autonomous vehicles demand both accuracy, precision, and high measurement frame rates. The optical transmitter must be able to generate high power pulses of very short duration, typically accomplished by driving a laser diode with very short, high current pulses. It has been shown that gallium nitride (GaN) power transistors are the primary choice for this application due to the large improvements in switching speed over silicon MOSFETs. However, the pressure to improve performance further still remains. This paper shows how to optimize layout to improve laser driver performance. It is shown that simply by changing the layout, that large improvements can be made in peak current and pulse width, as well as improved gate voltage waveforms.