Study On High Power All-solid-state Nd:YVO₄/LBO Green Laser

In the first chapter of this paper, all-solid-state green laser's main features and advantages, its field of application as well as the present development at home and abroad are introduced.In the second chapter, the operating principle of solid-state laser is analyzed. Based on the model of four-level system, the interacting theory between laser field and laser crystal is studied by the rate equation theory, then the characters, such as threshold power, output power, slope efficiency etc., of solid-state laser are deduced. The frequency conversion technique applied universally in the field of solid-state laser is studied: the second harmonic wave theory on the base of the coupled wave theory. The effect of phase-matching upon conversion efficiency is mainly analyzed.In the third chapter, the thermal lens effect of laser crystal is studied. The model of thermal lens theory and some measuring methods are explored. These methods are generalized and classified and the advantages and disadvantages of which are pointed out.In the fourth chapter, the coupling system between the fiber-coupled-output high power semiconductor laser acting as the pumping source and laser crystal is studied. By the method of matrix optics, the waist width and imaging distance of Gaussian beams through the coupling system are calculated. By the result of the calculation, a set of double planoconvex lens coupling system are designed and manufactured. The coupling efficiency is up to 92%. On the base of the coupling system, the mode matching between pumping laser and oscillating laser in the laser crystal is researched. The optimum position of focal spot of pumping laser through coupling system is calculated.In the fifth chapter, the optical characteristics of Nd:YVO4 and LBO are studied. The astigmatism problem of resonant cavity is explored thoroughly under the condition of thermal lens effect. Four-lens Z-folded cavity is designed and a set of perfect resonator parameters is screened out by the ABCD theory. With I type anglephase-match of LBO, Nd:YVO4 and LBO are controlled under the temperature of 20 ℃ and 18℃ respectively, and the total double-end pumping power is 26W, a maximum of 4.2W continuous wave green laser can be obtained and the optical-optical conversion efficiency is 17.6%; with I type noncritical-phase-match, Nd:YVO4 and LBO are controlled under the temperature of 20℃ and 148℃ respectively, the total double-end pumping power is 28.9W, a maximum of 8W continuous wave green laser can be obtained and the optical-optical conversion efficiency is 27.7%. We have designed the whole laser system and developed a prototype instrument which was checked and accepted by the department concerned. The final chapter is the summarization and suggestion of the paper.