Nonlinear Dynamics Of Diode-pumped All-solid-state Passively Q-switched Q Nd:LaMgAl₁₁O₁₉ Lasers

Diode-pumped all-solid-state passively Q-switched lasers excel in structure,conversion efficiency,stability,and other aspects,and also have the advantages of high output beam quality,high peak power,and narrow pulse width,making them important in scientific research,military defense,materials processing,and biomedical applications.The pulse characteristics of Q-switched lasers,such as width,energy,frequency,polarization,and wavelength range,are needed for these applications,and they also need to have good pulse peak power consistency.At present,the research of diode-pumped all-solid-state passively Q-switched laser mainly focuses on the single period dynamic state,while relatively little research has been done on lasers operating in other nonlinear dynamic states.Under certain operating parameters,passively Q-switched all-solid-state lasers can exhibit chaotic pulse states,and their output pulse peak power will exhibit a complex chaotic trend.Compared with other chaotic sources,pulsed chaotic lasers based on passively Q-switched all-solid-state lasers have higher peak power,and their applications in the field of chaotic radar are expected to significantly increase their range.Therefore,it is significant to investigate the nonlinear dynamics of diode-pumped passively Q-switched all-solid-state lasers.In this work,the principle of passively Q-switched is described theoretically,and the rate equation of passively Q-switched is analyzed.The output characteristics of the Nd:La Mg Al₁₁O₁₉ continuous-wave laser are studied first.Based on continuous-wave lasers,the passively Q-switched all-solid-state laser is studied deeply.The time series of diode-pumped all-solid-state passively Q-switched Nd:La Mg Al₁₁O₁₉ laser based on a semiconductor saturable absorber mirror is simulated numerically under different cavity losses.The simulation results show that the laser can operate in period-one,period-two,multi-period,and chaotic pulsing states when other parameters are fixed to change the cavity losses.We experimentally investigated the dynamic characteristics of a diode-pumped all-solid-state passively Q-switched Nd:La Mg Al₁₁O₁₉ laser based on a semiconductor saturable absorber mirror.For passively Q-switched all-solid-state lasers,when the type of gain medium and saturable absorber is fixed,the absorbed pump power and cavity loss are the key system parameters that affect the nonlinear dynamics of passively Q-switched solid-state lasers.The time series and spectrum were measured and recorded in the experiment,and the corresponding phase portrait was calculated.Several typical dynamics of the laser have been found by analyzing the time series,power spectrum,and phase portrait of the output laser at different parameters,and by gradually changing the key parameters,the laser will show a series of dynamical states.The detailed results are listed as follows:（1）When the cavity loss of the experimental system is fixed and the absorbed pump power is adjusted,the laser can operate at period-one,period-two,multi-period,and chaotic pulsing states in turn with the gradual increase of the absorbed pump power.The results show that the laser goes through period-one,period-two,and multi-period to chaos and the average output power increases gradually with the increase of absorbed pump power under a fixed cavity loss.（2）When the absorbed pump power is fixed and the cavity loss is adjusted,the laser can operate at period-one,period-two,multi-period,and chaotic pulsing states in turn with the gradual increase of the cavity loss.The results show that the laser goes through period-one,period-two,and multi-period to chaos and the average output power decreases gradually with the increase of cavity loss under an absorbed pump power of4.81 W.