High-Power, High-Repetition Short-Pulse Laser Driver using Direct-Drive D-mode GaN HEMT

This paper proposes a short-pulse laser driver using direct-drive depletion-mode gallium nitride high-electron mobility-transistor (DDD GaN HEMT) device. Known for its low on-resistance, high switching performance, normally-off operation, and reliability, DDD GaN devices are becoming popular in power applications. In this work, an in-house D-mode GaN HEMT with a blocking voltage of 200 V and on-resistance of 18 mΩ is used in a short-pulse laser driver for the optical phased array (OPA) applications. To achieve higher spatial resolution, the laser repetition rate must be in the tens of MHz range. Therefore, the dynamic behavior of device is first characterized by the double-pulse test. Additionally, the push-pull based laser driver actively controls the load capacitor charging time and the laser pulse width, thereby ensuring stable operation at high repetition rates. The output characteristics of switch-controlled (SC) short-pulse laser driver are simplified to switch turn-on time, stray inductance, and the input voltage. Finally, the experimental results achieved a short pulse width of less than 5 ns, high repetition rate of 50 MHz, propagation delay of less than 1.5 ns and peak power of 175 W, meeting the requirements for the specified object sensing application.