Operation of Laser–Diode Arrays

Compared to arc lamps, the electrical operating conditions of laser diodes are much more benign. The operating voltages are low and a trigger circuit is not required. Essentially, only a low-voltage dc power supply of the appropriate voltage and current range is required to operate the cw devices. Despite the very straightforward electronics, there are several challenges for operating laser diodes efficiently and reliably. The series resistance of laser diodes is very low; therefore, the internal resistance of the power supply must be minimized for efficient energy transfer.
Second, compared to flashlamps, laser diodes are electrically much more vulnerable.
Therefore, overvoltage, reverse bias, and current protection are essential features in the design of power sources. The power supply of a diode-pumped solid-state laser is the subsystem where most of the weight and volume savings occur compared to a flashlamp-based laser. High efficiency of a diode-pumped laser, low-voltage operation of the diodes, and the use of electrolytic capacitors for energy storage, allow the design of very small and compact power supplies.
In a pulsed diode-pumped solid-state laser system, the diode-array drivers replace the pulse-forming network in a conventional flashlamp-pumped laser system. The diode-array driver is a low-voltage switching network which supplies a constantcurrent pulse to the diode arrays. The low-voltage requirements for the diode arrays allow the use of power MOSFETs as switching elements. Electrical energy stored in electrolytic capacitors is transferred to the diode arrays on each laser pulse.