Numerical And Experimental Study Of High Power Acousto-optically Q-switched CO₂ Laser

Thanks to its high beam quality,wide range of power levels,stability of operation,etc.CO₂ laser has found lots of applications in microwave radar systems and industrial manufacturing.However,conventional CO₂ laser is usually working in continuous output mode or quasi-continuous mode excited by electric pulse,which significantly constrains further applications of CO₂ laser.Q-switching technology is a big breakthrough in the development history of laser.With high laser intensities in nanosecond pulses,Q-switched lasers are widely used in high precision material manufacturing such as metal cutting by largely reducing the heat effect.They also show better performance in radar systems and distance measurements.CO₂ laser operates in the infrared spectrum（within the atmospheric transmission window）,which is highly absorbed by organic chemical compounds.In contrast,few Q-switching devices working in infrared region has been reported,limiting the development of the Q-switching technique of CO₂ laser.To obtain pulses with higher intensities in CO₂ laser based on the currently available Q-switching devices,this thesis focuses on the numerical and experimental study of acousto-optically Q-switched CO₂ laser.First of all,the numerical solution of Q rate equation according to the four temperature model is calculated,we simulate the process of Q pulse,and research the influence of different relaxation parameters.Then,we build the experiment device of CO₂ laser acousto-optically Q-switching based on CO₂ laser tube.We get 1²1 W stable laser pulse output when repetition frequency ranging from 1⁵0 kHz.The peak power achieves 4.5 kW and pulse width is shorten to 200ns of 1 kHz PRF.We study the Q-switched laser pulse and power characteristics.At the same time,we do the pulse amplification experiments.Pulse power is amplified about 2.5 times.Finally,in order to get higher power Q-switched pulse,this paper proposes three mirror confocal unstable resonator.We calculate the normalized intensity distribution of this cavity by discrete FFT method and discuss the feasibility.And we do acousto-optically Q-switching experiments based on a fast axial flow CO₂ laser.