Study On Characteristics Of All-Solid-State Q-switched Lasers With V³⁺:YAG Saturable Absorber At 1.3μm

Although the flash-lamp-pump is not superior than the laser-diode-pump,it has a lot of advantages by itself,such as simple manufacture and operation,vile price and so on.Therefore,we have made some presentation and research about it in this paper. While,laser-diode-pumped solid-state lasers have become a focus in the field of lasers such as high efficiency,compactness,high stability,and long lifetime as well as healthy due to its advantages such as all solid state,high pump efficiency,small volume and long longevity,and has been paid much attention on.So it is of importance in the dissertation.In this paper,by using the Nd:YAG,Nd:GdVO₄(a-cut and c-cut)crystals as the gain mediums,V³⁺:YAG and acoustic-optic(AO) as Q-switched modulator,we have studied passively and actively Q-switched laser characteristics at 1.3μm in both numerical and experimental aspects.Meanwhile,the rate-equation model for the actively and passively Q-switched laser is given,and the numerical solutions of the rate equations are in agreement with the experimental results.By using a simple piano-concave cavity,we have demonstrated the 0.671μm laser performance of the LD-pumped both passively Q-switched with V³⁺:YAG saturable absorber and actively Q-switched with AO of intracavity-frequency-doubling Nd:GdVO₄/KTP red laser.In the theoretical analysis,a new rate-equation model is used to simulate the passively Q-switched operation in which the harmonic conversion is considered as a nonlinear loss of the fundamental wave.The main content of this dissertation includes:(â… ) Firstly,we have introduced the development process of the all solid state laser, and the gain mediums for flash-lamp-pump and laser-diode-pump.Secondly,we have related on the significance and prospect of all solid state Q-switched lasers at 1.3μm in brief.Thirdly,the laser Q-switched technique,the rate-equation model and the quasi-phase-matching theory to simulate the laser operations are related.(â…¡) We have presented the flash-lamp-pumped passively Q-switched performance of Nd:YAG,Nd:GdVO₄ laser with V³⁺:YAG saturable absorber at 1.319μm and 1.342μm respectively.For different small-signal transmissions of V³⁺:YAG,different reflectivities of the output mirror and different pump powers,the pulse energy,peak power,pulse width and repetition rate of 1.3μm laser have been measured.Both a-cut and c-cut Nd:GdVO4 crystals are used,and the output laser characteristics are compared.(â…¢) The performance of an LD-pumped Nd:GdVO₄ laser passively Q-switched with V³⁺:YAG saturable absorber has been realized.Meanwhile,a new rate-equation model for the Q-switched laser is given,in which the transversal and longitudinal distributions of the intracavity photon density,the transversal distributions of the population-inversion density,the saturable absorber ground-state population density and the pump beam are taken into account.The numerical solutions of the rate equations are in agreement with the experimental results.(â…£) We have demonstrated the performance of an LD-pumped double passively Q-switched Nd:GdVO₄ laser with V³⁺:YAG and Co²⁺:LaMgAl₁₁O₁₉ saturable absorber, and the dependences of the pulse width,pulse repetition rate,single pulse energy and peak power on incident pump power with three methods of Q-switching have been measured.Comparing to the performance of the single passively Q-switched Nd:GdVO₄ laser only using V³⁺:YAG saturable absorber,the results indicate that the double passively Q-switched laser can generate shorter pulses with higher single pulse energies and peak powers.In the theoretical calculation,a rate-equation model is firstly given to analyse the properties of the double passively Q-switched laser,in which the longitudinal distributions of the intracavity photon density and the pump beam are also taken into account.The numerical solutions of the equations are consistent with the experimental results.(â…¤) The theoretical and experimental studies in the LD-pumped doubly Q-switched Nd:GdVO₄ laser with AO and V³⁺:YAG have been presented.The doubly Q-switched output laser characteristics are measured under the AO repetition rates.It is shown that the higher peak power and more steadily repetition rate could be obtained; the pulse widthes of the doubly Q-switched laser are obviously compressed with higher single pulse energies and peak powers in contrast to the singly passively Q-switched laser with V³⁺:YAG.Meanwhile,the rate-equation model for the actively and passively Q-switched laser is given,and the numerical solutions of the rate equations are in agreement with the experimental results.(â…¥) By using a simple piano-concave cavity,we have demonstrated the 0.671μm laser performance of the LD-pumped both passively Q-switched with V³⁺:YAG saturable absorber or actively Q-switched with AO of intracavity-frequency-doubling Nd:GdVO₄/KTP red laser.The pulse width,pulse repetition rate,single pulse energy and peak power under different pump powers have been measured.In the theoretical analysis,a new rate-equation model is used to simulate the passively Q-switched operation in which the harmonic conversion is considered as a nonlinear loss of the fundamental wave.The main innovations of this dissertation are as follows:(â… ) We firstly realize the laser operations of the flash-lamp-pumped passively Q-switched Nd:YAG or Nd:GdVO₄ laser with V³⁺:YAG saturable absorber.The laser characteristics of 1.3μm laser have been measured.Both a-cut and e-cut Nd:GdVO4 crystals are used,and the output laser characteristics are compared.(â…¡) We have developed the new rate-equation model for the LD-pumped passively Q-switched Nd:GdVO₄ laser with V³⁺:YAG,in which the transversal and longitudinal distributions of the intracavity photon density,the transversal distributions of the population-inversion density and the pump beam are taken into account.By using this model,we firstly simulate the passively Q-switched operation with V³⁺:YAG saturable absorber,and the theoretical calculations are in agreement with the experimental results.(â…¢) We firstly realize the laser operations of an LD-pumped double passively Q-switched Nd:GdVO₄ laser with V³⁺:YAG—Co²⁺:LaMgAl₁₁O₁₉ saturable absorber, actively and passively doubly Q-switched Nd:GdVO₄ laser with V³⁺:YAG-AO.The laser characteristics are measured and the studies on the pulse width reduction is also presented.By considering the transversal and longitudinal distributions of the intracavity photon density,the population-inversion density and the pump beam,we firstly give a rate-equation model to analyse the performance of the doubly Q-switched lasers.The numerical solutions of the rate equations are consistent with the experimental results.(â…£) We firstly present systematically theoretical and experimental studies on the laser properties of an LD-pumped intracavity-frequency-doubling Nd:GdVO₄/KTP red laser Q-switched with V³⁺:YAG saturable absorber and Nd:GdVO₄/KTP red laser with AO modulator.By considering the harmonic conversion as a nonlinear loss of the fundamental wave,we firstly combine the phase-matching theory and the new rate-equation model to simulate the above-mentioned Q-switched operations.