Research On The Generation And Control Technology Of Q-switched Pulse Train Laser

Laser technology has shown great advantages and broad application prospects in the fields of precision guidance,laser fuze and laser detection,and has become a research hotspot at home and abroad.Correspondingly,the optoelectronic countermeasure technology developed for laser guidance,laser fuze and laser detection has also become the current key research direction.The research and development of lasers with good anti-interference performance in photoelectric countermeasures has become one of the key technologies in the field of photoelectric countermeasures.In view of this,this thesis studies a pulse train laser with unique coding function that can effectively resist laser interference and can be used for laser guidance,laser detection and laser fuze.On the basis of studying the generation and regulation technology of pulse train laser based on passive Q-switching method,according to the application requirements of laser guidance direction,the coding method of pulse train is further studied,which can significantly improve the anti-interference ability of laser guidance.The maincontents and research results of this thesis are as follows:1.Using rate equation theory,a numerical calculation model of passively Q-switched pulse train laser with Cr⁴⁺:YAG as saturable absorber is constructed.The generation process of the Q-switched pulse train is theoretically analyzed,and the pulse peak power,pulse width and single pulse energy of the laser output pulse train are theoretically calculated.The control technology of Q-switched pulse train is theoretically researched,and the reason of random fluctuation and relative fluctuation of Q-switched pulse train is theoretically analyzed.2.The Q-switching rate equation under the condition of pulsed pumping was numerically solved,and the process of generating active and passive Q-switching pulse trains was simulated.The simulation model of the Q-switched pulse train is producted,and the pulse train laser output is obtained.The laser pulse trains of passive Q-switching and electro-optical Q-switching under the condition of pulse pumping are compared and analyzed.The effect of different pump waveforms on the interval between adjacent sub-pulses in the pulse train output by the laser has been calculated and simulated.For the single pulse energy,peak power,pulse width,first pulse settling time,each pulse train output by the laser under different pump frequencies,different cavity lengths,different pump durations,different pump powers and different reflectivity of output mirrors.The influence of factors such as the number of sub-pulses of each pulse train and the energy conversion efficiency in the process of Q-switching on the output characteristics of the pulse train is analyzed and simulated.Therefore,a method for controlling the number of sub-pulses is obtained,so that the code pattern can be changed by adjusting the laser parameters for encoding;at the same time,a method for increasing the output pulse energy,shortening the pulse width and improving the Q-switching efficiency is also obtained.Improve the pulse performance of the output pulse.3.An experimental research platform for passively Q-switched pulse train lasers was built,and under the guidance of experimental results and theoretical simulation data,further research on the conditions of different cavity lengths,different pump durations,different pumping powers and different initial transmittances of Cr⁴⁺:YAG is carried out.The single-pulse energy,peak power,pulse width,number of sub-pulses of each pulse train and Q-switching efficiency of the laser output pulse train were studied,and the regulation rules of pulse trains under various conditions were obtained,which verifies the control scheme obtained in simulation research.4.On the basis of the experimental research on the pulse-pumped passively Q-switched pulse train laser,it is found that under certain conditions,when the pump power and pump duration are changed,the single pulse peak power of the same pulse train will fluctuate randomly,and this kind of random fluctuations can recur periodically in different bursts.By analysis this phenomenon and combining with pulse coding technology,an anti-jamming coding application scheme of pulse-pumped passively Q-switched pulse train laser is proposed,and its feasibility is analyzed and verified.