Research Of Nd:YLF Laser Amplifier Side-pumped By High Power Laser Diode Array

Because of the advantages of high energy conversion efficiency, high stability, small size, high quality, high repeated frequency, long fluorescence life, all-solid-state et al, the diode pumped solid-state laser (DPSSL) has been the development hotspot of new kind of laser. By using laser diode array (LDA) to replace Xe lamp to pump medium, DPSSL can also overcome the serious thermal effects and other side-effect of Xe lamp. Nd:YLF crystal has longer fluorescence life and natural birefeingent, and can exert the potential of power-restricted LD.Here the basic amplifing characters of Nd:YLF laser amplifier side-pumped by high power laser diode array are analyzed and researched based on theory and experiment. The main content is the following:1 By using Overlap Integral and covey equations, the amplifing characters of laser amplifier are analyzed. The characters of gain, energy conversion efficiency, and output energy are studied based on theory and simulation in detail.2 A Nd:YLF laser amplifier and a suit of two-stage double-pass off-axis amplifying system are designed, made, and operated successfully. The laser amplifier is side-pumped by high power laser diode array. The temperatures of laser diode array and Nd:YLF rod are controlled effectively and the accurate delay is adopted. Such measures increase the energy conversion efficiency and stability of amplifier. The relations of gain, energy conversion efficiency, output energy and pump current, delay between amplifying pulse and current of amplifier, input energyare received based on experiment.The results of experiment indicate: the laser amplifier with side-directly-pumped coupling system has uniform pump light distribution and gain distribution. As input energy is 20 J, the gains of two amplifiers are 5.35 and 5.25. As input energy is 27 J after the 5mm 5mm soft diaphragm, the two- stage double-pass off-abaxial small-signal net gain of amplifying system is 600, output energy is 5.7mJ, and energy extract efficiency is 0.86%. As input energy is 1.58mJ,the output energy of amplifying system is 129.2mJ, and the energy extract efficiency is 19.5%.3 The transient temperature distribution in the Nd:YAG laser rod repeating pulse-pumped by high power ring-LD array is simulated in detail by using ray tracing method and finite element method. The transient temperature distributions at different pump periods, pump frequencies and pump widths are analyzed and compared. The result indicats that when high power ring-LDA pumps repeatly, the core temperature of the rod has sawtoothed distribution, and the temperature of the rod rises as the pump frequency or pump width rises. At last the temperature has periodical distribution with time.4 A electro-optics Q-switch oscillator side-pumped by high power laser diode array is adopted to produce amplifying pulse. The oscillator has original double-step Q switch driver and low-voltage KTP crystal as the electro-optics switch. The results of experiment indicate that: The time dither of output pulse of electro-optics Q-switch oscillator is less than 4 ns, pulse width is less than 6.7ns, output energy is 1.16mJ, single-longitudinal mode probability is 100%, energy stability of single pulse is 3%, and stability of pulse width is 4%.The amplifying characters of a Nd:YLF laser amplifier side-pumped by high power laser diode array are analyzed and researched in detail based on theory and experiment. The results can offer references to design, develop, and optimize solid-state laser amplifier side-directly-pumped by high power laser diode array.