Generation Of Pulsed Vortex Beam In Off-axis Pumping Solid-state Laser

It is an important method to excite Hermite-Gaussian(HG)beams in the resonator and convert them into Laguerre Gaussian(LG)beam.This method has the advantages of simple structure and high mode quality.In this thesis,high power pulsed vortex beams are generated by off-axis pumped solid-state lasers.The model of multimode oscillation rate equation for off-axis pumped solid-state laser is established.The relationship between mode distribution and off-axis quantity,pump radius and pump power is studied by numerical calculation.The results show that when the pump spot radius is small,a single mode output can be obtained,and the mode outputs alternately as the off-axis amount increases.When the radius of the pump spot is large,the modes cannot appear alternately.In the process of multimode oscillation,when the pump power is near the threshold,the output power of each mode presents complex fluctuations.When the pump power is much higher than the threshold power,the output power of each mode increases linearly with the pump power,and the mode ratio basically remains unchanged.The results can provide reference for the design of high power off-axis pumped solid-state lasers.The experimental system of off-axis pumped continuous solid-state laser is designed and established,and the relationship between output mode and off-axis quantity is studied.The experimental results show that with the increase of pump power,the off-axis value of each mode needs to be corrected.Theoretical analysis shows that this is caused by the decrease of effective off-axis amount caused by off-axis thermal lens.Continuous HG60?HG70 mode beams are produced in the experiment.The power of HG10 beam,HG20 beam and HG30 beam can reach 1.58 W,1.43 W and 1.31 W respectively.The experimental system of off-axis pumping acousto-optic Q-switched solid-state laser is established.The pulsed HG beams are generated,and the LG10,LG20 and LG30 mode vortices are obtained by mode conversion.At 10 kHz repetition rate,the average power of the three modes is 1.31 W,1.23 W and 1.14 W.And the pulse width is 50.33 ns,51.62 ns and 54.75 ns,respectively.The corresponding single pulse energy is 0.13 mJ,0.12 mJ and 0.11 mJ,and the peak power is 2.6 kW,2.3 kW and 2.0 kW,respectively.