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Ld Side-pumped Polycrystalline Nd: Yag Ceramic Bbo Electro-optical Q-narrow Pulse, Green, Ultraviolet Laser Research

Posted on:2011-06-03Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y BaiFull Text:PDF
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The combining of semiconductor laser array with technology of side-pumping laser gain medium, nonlinear frequency conversion and Q-switching make the novel all-solid-state laser can achieve high power, high repetition rate arid narrow pulse width high qualified laser pulse with the wavelength range from far infrared-visible light to deep-UV. The novel all-solid-state laser has advantages of compact structure, high energy conversion efficiency, high reliability, light weight and good beam quality compared with other traditional lasers such as gas, chemical and free electric laser devices, so it is always used in the forefront of laser science and technology research and has been widely used in industrial precision machining, medical treatment, laser communication, laser radar, laser ranging, thermonuclear reaction and many other areas.In order to obtain the high peak power, high repetition rate, narrow pulse width green laser at 532nm and the UV laser at 355nm with high pulse energy, narrow pulse width, in addition the high quality stable output deep UV 266nm laser the theoretical and experimental researches in the article worked as follows:1. Simulated the light intensity distribution in the LD multi-side-pumped Nd:YAG ceramic rod. Take LD pumping in 5 directions as the example:the thermal scattering and the distribution variation law of LD pump light in ceramic rod was simulated in different conditions of rod radius, absorption and convergent pump light spot radius; the lengths of thermal lensing of the LD continuously pumped ceramic rod was derived through matrix, the lengths of the thermal lens were carried out under different pumping power; a simple method to measure the thermal length of laser ceramic rod lens was designed and it was used in polycrystalline Nd:YAG ceramic rod, which can be pumped by 808nm laser at the maximum power of 300 watts, thermal lens length measuring.2. A model for laser output character variation was established based on rate equation of electro-optical Q switching. Models of theoretical heat transport and thermo elasticity were established for demonstrating temperature distribution and thermal stress in the electro-optical crystal. After the simulating and analysis of temperature distribution and thermal stress in these four type normal crystal KD*P, LiNbO3, BBO and RTP by finite element analysis method, BBO electro-optical crystal was chosen for the experiment.3. Based on the refractive index equation, the phase-matching curve, effective nonlinear frequency-doubling coefficient and discrete angle spatial distribution characteristics of 532nm green laser, which come from 1064nm fundamental light frequency-doubled through KTP or LBO were simulated and analyzed in the experiment; then the best phase-matching orientation,which is also called the best phase-matching angle, in KTP and LBO crystal for typeⅠand typeⅡwere got, and so did the effective nonlinear frequency-doubling optical coefficient and the walk-off angle along the best phase matching direction. Finally LBO was chosen for the experimental research after comparison and analysis.4. Waged the experimental study on BBO electro-optical Q switched high-repetition-rate, high power and narrow pulse green laser that generated by LBO intracavity frequency doubling continuous LD side-pumped Nd:YAG ceramic. From the theoretical analysis of astigmatism problem in V-folded resonator, the resonant cavity structural design software was used for V-cavity astigmatism compensation, stability and structural optimization design; then by parameters of the resonant cavity structure simulating s polarized quasi-continuous green laser achieved the maximum average of 32.6 W and 58.5 ns pulse width during the best electro-optic Q-repetition rate of 10.2 KHz.5. Finished the experimental study on LD pulsing side-pumped Nd:YAG ceramic/BBO electro-optical switched/LBO outer extra-cavity frequency doubling UV laser with high energy and peak power with narrow pulse width.①By using linear resonant cavity, pulsed LD side-pumped polycrystalline Nd:YAG ceramic, BBO electro-optical BBO synchronous switching, LBO outer extra-cavity frequency doubling & summing technology 355 nm UV narrow pulse of 5.25ns with maximal single pulse energy at 23.4 mJ and highest peak power at 4.46MW was obtained during at the pump current at of 120 A and Q switch repetition rate at of 1 Hz; when at the repetition rate of 20 Hz, the maximal average and peak power of 355 nm pulse respectively achieved 245.6 mW and 1.1 MW and its pulse width is about 11.2 nm wide, the 1064 nm infrared laser pulse at of 663.6 mW and 532 nm green laser pulse at of 335.5 mW was gained obtained simultaneously by using a spectroscope.②Based on the mentioned above, when replacing frequency summing crystal with typeⅠBBO, which used as 4 times frequency doubling crystal, the 266 nm UV pulse width of 4.66 ns pulse laser was generated at the pump current of 120A and repetition rate at of 1 Hz, its maximal single pulse energy and peak power are respectively 18.4 mJ and 3.95 MW; during the repetition rate varying to 20 Hz the width of 266 nm UV pulse is 10.1ns and the maximal average power and peak power respectively achieved 185.5 mW and 0.92 MW, the 1064 nm infrared laser pulse at 820.2 mW and 532 nm green laser pulse at 384.5 mW was obtained by using a spectroscope.
Keywords/Search Tags:continuous LD side-pumping, pulsed LD side-pumping, polycrystalline Nd:YAG ceramic, BBO electro-optical Q switching, green light, ultraviolet light, high average power, narrow pulse width, high peak power
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