Research On Slab Lasers Nonuniformly Pumped By Laser Diodes

This thesis focuses on slab lasers nonuniformly pumped by laser diodes.First the thesis presents a new design principle of slab lasers as the designcriteria with nonuniform pumping profile, that is, the laser design focuses on outputpower, efficiency and beam quality, instead of going after good pumping uniformitywithin the gain medium, since the traditional one pursues the uniform pumpingdistribution, which, however, has not been realized in most cases but increases thecomplexity and cost. To begin with the core physical issue of the nonuniformpumping, the thesis investigates the variation of absorption cross section of the gainmedium as temperature changes and reports the experimental measurement results,demonstrating the coupled relationship among the temperature distribution,absorption coefficient distribution and absorbed pump power distribution within thenonuniformly pumped slab lasers. Based on the coupled relationship, the thesisdevelops an iterative cycle method for the analysis on high power solid-state lasersand corrects the errors from the traditional theoretical models. With the revised model,research on nonuniformly pumped slab lasers in terms of high average powerend-pumped slab, high average power side-pumped slab, and high beam qualityend-pumped slab are individually carried out to explore the feasibility of the designprinciple with nonuniform pumping profile.High average power end-pumped zigzag slab laser with nonuniform pumpingprofile is firstly studied. Experiment on continous-wave slab oscillator generatesmultimode laser output of402W, with the optical-optical efficiency of34.6%, whilethe amplifier experiment, by employing a novel MOPA configuration with thecombination of two different gain mediums, realizes pulsed output with both highpulse repetition rate (500kHz) and high pulse enegy (1mJ). It should be noted thatthe pulse energy of1mJ is the highest value ever reported, obtained in lasers withpulse repetition rate higher than200kHz. The research indicates that the slab laserwith nonuniform pumping profile is capable of power scaling and obtaining the output with high average power.High average power side-pumped slab laser with nonuniform pumping profile isthen studied, since the end-pumped slab laser has the weak point of low pumpintensity per unit volume and small area of pump window. Two novel configurationsas the single-side-pumped slab laser amplifier chain and the distributed-side-pumpedslab laser are presented, while the parameter design as well as the feasibility of powerscaling is discussed in detail, predicting a10kW of output power from asingle-side-pumped chain that contains20slabs, and a1kW of output power from adistributed-side-pumped slab laser with5slab units. The research shows that bothnovel designs indeed have the practicability and application value.In the end the fundamental-mode nonuniformly pumped slab laser isinvestigated. With theroretical optimization and experiment, the TEM00laser outputfrom the quasi-concentric laser resonator with line-shaped end-pumping profile, iscorrected for astigmatism, and symmetrized in horizontal and vertical directions interms of beam quality, waist radius and waist position. In addition, a12.2W pulsedTEM00output is obtained at the repetition rate of30kHz.