Subnanosecond Marx Generators for Picosecond Gain-Switched Laser Diodes

High precision time-of-flight based light detection and ranging (LiDAR) system needs compact ultrafast pulsed lasers, such as gain-switched semiconductor laser diodes, which have the advantages of low cost, small size, and mass-producible, for short pulse generation, and are of great interest in many other fields, where low-cost high-voltage electrical pulse generators are in demand to directly modulate laser diodes for practical applications. Here, we presented a low-cost subnanosecond electrical pulse generator based on avalanche transistors, with output electrical pulses having a maximum peak voltage of approximately 25 V and a minimum pulse width of approximately 450 ps, depending on load impedance. We applied the electrical pulses on a gallium nitride (GaN)-based blue-violet laser diode, and demonstrated typical gain-switching characteristics of the laser diode. The minimum pulse width of the first spike of the gain-switched optical pulses was as short as 23 ps. In addition, we constructed a field-programmable gate array (FPGA)-triggered Marx generator with programmable frequency, and demonstrated its practicability in characterizing the transient gain-switching properties of laser diodes with a streak camera. These results should be of significant interest for both industrial applications and scientific research.