Beam Quality Of Laser Diode

The configuration and principle of laser diode and its mode field distributions, several methods for evaluating beam quality are discussed. Furthermore, a new method for evaluating beam quality of laser diode is proposed.The main work of this dissertation is summarized as follows1. Several methods such as focused spot size, far-field divergence angle, times diffraction limited factor β, Strehl rate, energy circle rate and M2 factor are summarized. The application range, strongpoint and shortcoming of them especially used in evaluating beam quality of laser diode is also analysed.2. The main factors to influence collimating the beam of laser diode with lenses are analysed. A new quality parameter(QP) lθ5 (l is the size of the emitter in the direction parallel to the junction plane, θ is the angle of the beam in the perpendicular direction.) for evaluating beam quality of laser diode is given. The difficulty of collimation is well expressed by use of QP. The smaller the value of lθ5 is, the more easily the beam is collimated. Furthermore we give a reference value of the QP, when the QP value of the beam is smaller than this value, this beam can be collimated without much difficulty. And another assistant parameter astigmatism factor Xs is also given to evaluate the difficulty of collimating the beam of laser diode.