Study On The Optimization Of Parameters Of Double Q-switched Lasers With AO(EO) And A GaAs Saturable Absorber

Laser-diode(LD) pumped Q-switched laser can generate narrow pulse with high peak power and repetition rates, which has wide applications in the fields such as information storage, remote-sensing detection, laser telecommunication as well as healthy. In some applications, the pulse energy, peak power and pulse width of double Q-switched laser are very important parameters. As far as we know, the optimization of peak power and pulse width of doubly Q-switched lasers with both an AO modulator and a GaAs saturable absorber has not been reported. The optimization of pulse energy, peak power and pulse width of doubly Q-switched lasers with both an EO modulator and a GaAs saturable absorber has also not been reported.In this dissertation, by using the normalized rate-equation of doubly Q-switched lasers with both an AO modulator and a GaAs saturable absorber, set up by Li etc, the research on the optimization of the peak power and the pulse width in the doubly Q-switched lasers with both an AO modulator and a GaAs saturable absorber has been carried out, and the optimal results are validated in the experiment. Then we modify the above model and use the new model to optimize the pulse energy, peak power and pulse width of doubly Q-switched lasers with both an EO modulator and a GaAs saturable absorber, the optimum parameters obtained above can help us in the design of these all solid-state Q-switched lasers.The main contents of this dissertation include:1. The research on the optimization of the peak power in the doubly Q-switched lasers with both an AO modulator and a GaAs saturable absorber has been carried out, the key parameters of an optimally coupled doubly Q-switched laser are determined based on maximizing the peak power and a group of general curves are generated for the first time. The curves clearly show the dependence of the optimal key parameters on the parameters of the gain medium, the GaAs saturable absorber, the AO Q-switch, the resonator, and the spatial distributions of the intracavity photon density. These results are compared with those of the optimized doubly Q-switched laser with both an acousto-optic modulator and a GaAs saturable absorber based on maximizing the output energy, and the differences are also discussed. For a given pump power with different reflectivities of the output mirror and different small-signal transmissions of GaAs saturable absorber , the pulse energy, peak power and pulse width in a diode-pumped Nd:YVO4 laser with both an AO modulator and a GaAs saturable absorber have been measured. Comparing the experiment results with the theoretical results, they are in agreement with each other.2. The research on the optimization of the pulse width in the doubly Q-switched lasers with both an AO modulator and a GaAs saturable absorber has been carried out, the key parameters of an optimally coupled doubly Q-switched laser are determined based on maximizing the peak power and a group of general curves are generated for the first time. The curves clearly show the dependence of the optimal key parameters on the parameters of the gain medium, the GaAs saturable absorber, the AO Q-switch, the resonator, and the spatial distributions of the intracavity photon density. These results are compared with those of the optimized passively Q-switched laser with Cr⁴⁺-doped saturable absorber based on maximizing the pulse width, and the differences are also discussed. Making use of these expressions and curves, we can forecast its pulse characteristics and the optimum parameters obtained above can help us in the design of optimized double Q-switched lasers.3. We modify the normalized rate-equation of doubly Q-switched lasers with both an AO modulator and a GaAs saturable absorber which is set up by Li etc. Using this new model, we theoretically study on the optimization of the characteristics in a LD-pumped doubly Q-switched laser with both an electro-optic modulator and a GaAs saturable absorber. The key parameters of an optimally coupled doubly Q-switched laser are determined based on maximizing the peak power, peak power, pulse width and a group of general curves are generated for the first time. The curves clearly show the dependence of the optimal key parameters on the parameters of the gain medium, the GaAs saturable absorber, the EO Q-switch, the resonator, and the spatial distributions of the intracavity photon density. These results are compared with those of the optimized doubly Q-switched laser with both an acousto-optic modulator and a GaAs saturable absorber based on maximizing the peak power, peak power and pulse width. Making use of these expressions and curves, we can forecast its pulse characteristics and the optimum parameters obtained above can help us in the design of optimized double Q-switched lasers.