Investigation Of Diode-Pumped Slab Module

Solid-state lasers traditionally are fabricated in the shape of a long thin rod, which exhibits optical distortions such as thermal focusing, thermal stress induced birefringence in the case of high power operation. These thermally induced effects severely degrade the optical quality of the laser beam and eventually limit the laser output power. Both theories and experiment results show that novel slab lasers are of advantage to eliminate those thermal focusing effects, improve the optical quality and increase the output power. This dissertation presents results of edge-pumped slab module based on a series of theoretical and experimental researches. The contents can be outlined as follows:(1) The advantages of slab lasers are reviewed. The ordinary gain mediums and pumping techniques are described. The development of LD pumped slab lasers in China and foreign countries are summarized.(2) Theoretically induced temperature and stress distributions of both face-pumped slab laser and edge-pumped slab laser, compared with rod geometry medium.(3) Based on finite element (FE) analysis, the thermal effects of edge-pumped Nd:YAG slab module have been studied in detail, and the temperature and thermal stress distributions in the slab medium have been analyzed and compared. There is not much difference between temperature and thermal stress of one-side pumping and two-side pumping methods. But by using two-side pumping method, it's easy to achieve symmetrical temperature distribution, and the central temperature of the pumping face grows lower when the size of the pump beam becomes bigger. Great thermal stress exists on the edge and border of the slab, which is susceptive of fracture in the case of high pump power. The stress introduced by the mechanical operation must be paid attention to.(4) LD edge-pumped slab module is developed, with the test experiments on the thermal effects and the depolarization. It is found in the experiments that the uniform thermal stress distribution which exists in the central place of the slab may eliminate the depolarization effectively, but on the edge of the slab, there is some depolarization. The focal lengths in the thickness direction and the width direction are 0.75m and -7m respectively, with the pump power of 68W.(5) According to the experiment results, the resonator of the LD edge-pumped slab laser is discussed, which is the theoretical and experimental base of the resonator design.