The Performance Of Diode-end-pumped Nd:GGG Lasers

With the development of the laser technique,lasers are widely used in fields of industry,medical treatment,military and our daily life.Diode pumped solid state lasers(DPSSL) have become the central focus of the field of lasers due to their many advantages such as compactness,high efficiency,high stability,etc.Laser crystal is an important part of laser system,in this dissertation,by using the fiber-coupled laser-diode as the pump source,Nd:GGG and Nd:CLTGG crystals as the gain mediums,we have studied the performance of the actively Q-switched lasers of 1062nm as well as 1331nm with acoustic-optic(AO) modulator,and passively Q-switched lasers with Cr⁴⁺:YAG,Co²⁺:LMA and V³⁺:YAG saturable absorbers, respectively.And we also have studied the performance of the diode-end-pumped Nd:GGG red and green laser by using frequency doubling crystals of KTP and LBO. In addition,by using Cr⁴⁺:YAG,Co²⁺:LMA and V³⁺:YAG as the intracavity mode-locker,respectively,the simultaneously Q-switched and mode-locked lasers have been realized.Meanwhile,the coupling rate equations under Gaussian distribution approximation have been used to theoretically analyze the properties of the above-mentioned Q-switched lasers as well as the simultaneously Q-switched and mode-locked lasers.The main content of this dissertation includes:(1)We have summarized the physical,chemical,mechanical and optical characteristics of the crystal of Nd:GGG.And we have measured the intrinsic loss,thermally induced loss and thermal focal length of the crystal.The experimental results were consisted with the calculated results.(Chapter 2)(2) We have demonstrated the diode-end-pumped Nd:GGG continuous lasers of 1062nm,1331nm and 938nm.(Chapter 3)(3) We have studied the performance of the actively Q-switched lasers of 1062nm.The maximum output power of 2.34W was obtained.The maximum pulse energy of 366μJ,the maximum peak power of 12.9kW,and the minimum pulse width of 28ns were obtained,respectively.We have studied the performance of the actively Q-switched mode-locked lasers of 1062nm.The maximum average output power of 2 3.32W was obtained,the conversion efficiency from CW to Q-switched mode locked was 30.2%.The mode locked pulse width was estimated to be 120ps.The experimental results were consisted with the calculated ones.(§4.2,§4.3)(4)We have studied the performance of the diode-end-pumped Nd:GGG green lasers by using frequency doubling crystal of KTP.The maximum average output power The maximum output power of 660mW was obtained,and the frequency doubling efficiency was 23.7%.We have studied the performance of the actively Q-switched mode locked lasers of 1331nm.The maximum average output power of 1.73W was obtained the conversion efficiency from cw to Q-switched mode locked was 13.3%. We have studied the performance of the diode-end-pumped Nd:GGG red lasers by using frequency doubling crystals of LBO.The maximum of average output power of 378mW of red laser was obtained.We also have studied the performance of the diode-end-pumped Nd:GGG red lasers by using frequency doubling crystals of KTP, the maximum average output power was 388mW,the minimum pulse width was 226ns,the maximum single pulse energy and the maximum peak power were 63.8μJ and 284W respectively.(§4.4,§4.5,§4.6)(5) By using Cr⁴⁺:YAG crystals as the saturable absorber,the Q-switched lasers of 1062nm have been realized.The maximum average output power 2.87W and 2.63W were recorded with initial transmission of 90%and 85%,corresponding to the conversion efficiency from CW to Q-switched of 84.7%and 77%,respectively.When the initial transmission was 70%,the minimum pulse width was recorded to 4ns,and the corresponding maximum single pulse energy and peak power were 206μJ and 51.6KW,respectively.(§5.2)(6) By using Co²⁺:LMA as the saturable absorber,the Q-switched lasers of 1331nm have been realized.A maximum average output power of 183 mW was recorded with a Co²⁺:LMA SA with initial transmission of 90%.By using a V³⁺:YAG crystal with initial transmission of 94%as the saturable absorber,the maximum average output power of 460 mW,the minimum pulse width of 19 ns and the repetition rate of 39 kHz were achieved,corresponding to pulse peak power of 0.62 kW and single pulse energy of 11.8μJ,respectively.(§5.3,§5.4)(7)By using Cr⁴⁺:YAG crystal as the saturable absorber,a diode-pumped passively Q-switched and mode-locked Nd:GGG laser operating at 1062nm was realized.The maximum output power of 1.38W and the Q-switched pulse energy of 51μJ were obtained when the initial transmission of Cr⁴⁺:YAG crystal was 85%。When initial transmission of Cr⁴⁺:YAG was 76%,the maximum average output power of 0.7W and the pulse energy of 65μJ were obtained.The space-dependent rate equations which describe the mode-locking process were solved numerically,the theoretical calculations reproduced the laser characteristics well.(§6.2)(8) By using Co²⁺:LMA crystal as the saturable absorber,a diode-pumped passively Q-switched and mode-locked Nd:GGG laser operating at 1.3μm was realized.The mode-locking modulation depth of nearly 100%has been achieved.The maximum output power of 103mW and the Q-switched pulse energy of 8.41μJ were obtained.By using V³⁺:YAG crystal as the saturable absorber,The maximum output power of 410mW and the Q-switched pulse energy of 8.3μJ were obtained.The theoretical calculations reproduced the laser characteristics well(§6.3,§6.4)(9) The diode-end-pumped Nd:CLTGG lasers have been studied.The absorption spectra, luminescence spectra and the luminescence life time of Nd:CLTGG crystal has been summarized.The maximum output power of CW laser of 1.32W was obtained for the first time.The solpe efficiency was17.1%.By using Cr⁴⁺:YAG crystal with initial transmission of 95%as the saturable absorber,the maximum average output power of 91mW was obtained,the minimum pulse width was 16.3ns,the single pulse energy and the peak power were 35.1μJ and 2.16kW respectively.(Chapter 7)The main innovations of this dissertation are as follows:(1) For the first time,we have measured the intrinsic loss,thermally induced loss and thermal focal length of the diode-end-pumped Nd:GGG crystal.The experimental results were consisted with the calculated results.(2) We have studied the performance of the actively Q-switched and actively Q-switched mode locked lasers at 1062nm and 1331nm.And studied the performance of the diode-end-pumped Nd:GGG red and green lasers by using frequency doubling crystals of KTP and LBO.(3) By using Cr⁴⁺:YAG,Co²⁺:LMA and V³⁺:YAG crystals as the saturable absorbers,the diode-pumped passively Q-switched and mode-locked Nd:GGG laser operating at 1062nm and 1331nm were realized for the first time.(4) For the first time,the diode-end-pumped Nd:CLTGG lasers has been studied,and by using Cr⁴⁺:YAG crystal as the saturable absorbers,a diode-pumped passively Q-switched Nd:CLTGG laser operating at 1.06μm was realized for the first time.