Study On Beam Characteristics Of High-Power Diode An Its’ Applications In Diode Pumped Solid State Lase

In recent years high-power laser diode and bar and stack lasers have been usedwidely in the industrial、military fields as pumping source of solid-state lasers. Beacuseof the waveguide properties of their active areas, the beam quality of a high-power laserdiode is poor.The high-power laser diode is mainly used in diode pumped solid statelaser(DPL)as pumping source. For the reason of big change in laser medium, theinfluence to the oscillating laser is much more than to the lamp pumped solid state laser,the study on the question about how the pumping light affect the performance of adiode pumped solid state laser is necessary, and with the development of miniature DPL,and how to improve the quality is also discussed.The propagation of a high-power laser diode and its’ application in DPL areanalyzed in this dissertation. A model to describe the vector far-field propagation of ahigh-power laser diode is given; the discussion of the field about the bar and stack,andhow the pumping light affect the diode pumped solid state laser are discussed; Finally,we analysised the directly coupled pumping technique.1. For the high-power laser diode, which works in the TM-mode state, the vectornonparaxial theory and a simple mathematical expression to describe the propagation ofa high-power laser diode are proposed. The analysis of the relative error yielded by thescalar approximation of the laser diode beams is presented. The results indicate that wemust consider the vector properties of the far-field distribution, when we need toaccurately describe the far-field propagation of a TM-mode high-power laser diode,especially in the nonparaxial region.2. The bi-peak model is applied to describe the field distribution for both bar andstack lasers, and the far-field intensity of each emitter are superposed non-coherently,then the far-field intensity model of the bar and stack lasers are obtained. According tothis model, the far-field intensity distribution of the real bar and stack is simulated. Forbar and stack, quantitative descriptions of both homogeneously-distributed regions andthe position where the distribution is similar with bi-peak distribution emitted by asingle emitter are given. The corresponding experienced formulas are also presented. Bythese formulas and the parameters given in the datasheet, the homogeneously-distributed regions and the position can be easily found. The results of this paper can beuseful for the design of optical systems and the evaluation of the laser beam’s quality in the practical application.3. The diffraction theory of resonators with the pumping gain is discussed in thepresent work; the results show that the pumping light can strongly affect the oscillatinglaser even in plane-plane cavity. In specifically, how the distribution of pumping lightand the size of pumping light, and the power of pumping light affect the oscillating laserhas been analysed. In practice, to design better DPL we should optimize the pumpinglight based on the need of the oscillating laser.4. Direct pumping technique of micro-modularization DPL is studied. The pumpdistribution of laser diode in gain medium is obtained and analyzed. The optimalpumping distribution in the gain medium is discussed. Bsed on the rate equation of fourlevel systems, the simulation of side pumped Nd: YAG laser is established. Computedresults indicate that the position of the pumping LD can influence the beam quality M2.An experimental equipment of laser diode symmetrically side-pumped Nd: YAG laser isdesigned.