Study On High-power Laser Diode's Divergence Angle Testing System

As the extensive application of the semiconductor laser diode (LD), it becomes more and more important to evaluate the quality of laser beam. Laser's space beam parameters, such as intensity distributing, beam diameter, divergence angle, beam stability, are very important parameters for evaluating the quality of laser beam, which also deeply influence the laser application. Divergence angle is a significant parameter. It characterizes the beam propagation character and the beam ray-trace method in the distance. It is not only an important parameter to evaluate the quality of laser beam, but also an important foundation for beam collimating system design.The paper presents a novel method for divergence angle measuring, based on geometry characteristic of two facula curves detected at the different positions to the laser. Facula curves are gained by two hemicycle probes' scan. Two probes have different radius. This testing method resolves a key problem that probe is shattered or burned because of high power while scanning across the beam section. The paper gives the whole system based on this method including computer software, USB interface, single-chip controller module, data collection module and step motor module. The step motor drives the light taking-in fitting to detect the power of laser across the beam section. The facula spot edges are acquired after data processing and then the divergence angle is calculated.With the testing system and a 1000W high-power laser diode array, a series of experiments are conducted. It has been proved by the experiments that the testing system can be used to measure the divergence angle of high-power laser diode array and the accuracy is 0.1°, which is able to be applied in practice.