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High-power Ld Side Of The Pump Quasi-continuous Intracavity Frequency Doubling Of All-solid-state Green Laser Research

Posted on:2009-09-06Degree:DoctorType:Dissertation
Country:ChinaCandidate:H W ChenFull Text:PDF
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All-solid-state laser has been a new research develops and applies in the international laser industry because of its characteristics of high energy, long life-time, well-orientation, good monochromaticity and coherence. The dissertation is around the study on "The quasi-continuous-wave (QCW) green beam generation by intra-cavity-frequency-doubling of diode-side-pumped", this dissertation elaborately introduces the characteristic of gain distribution, temperature distribution, thermal lens effect and thermal birefringence effect. and the dynamic characteristics of the resonator is also discussed. In addition, the theoretical analysis and experimental research on Quasi-continuous-wave (QCW) green beam generation by intra-cavity-frequency-doubling of diode-side-pumped solid-state-laser in a two-rod V-shaped cavity are demonstrated, including the industrialization. The main content of this dissertation can be outlined as:1. The development process of all-solid-state lasers is reviewed, and the recent research evolution of LD pumped solid-state green lasers has been summarized at home and abroad.2. The theoretical basis of all-solid-state lasers is retrospected to develop high power solid-state green laser. The steady state equations of m-transverse-mode oscillating in diode-side-pumped lasers are investigated based on the theory of rate equation. The factors, which would influence on the average output energy, peak power, pulse width and waveforms of DPSSL, are discussed through analyzing the rate equation of active-Q-switched pulsed laser pumped by diode laser. The principle and basic structure of the acousto-optic modulator are also introduced. The principles of the second harmonic generation in the nonlinear crystal polarized by the fundamental wave and the sum frequency generation have been studied.3. The temperature distribution in the laser medium pumped by diode-laser is analyzed. Several factors leading to thermal lens effect are investigated and the changing trend of thermal focal length versus pumping current is presented under the condition of high power laser. The thermal stress, as well as its distribution in the laser rod, the forming reason and the corresponding compensation method, is discussed. According to the experimental objective and the conditions available, the cavity configuration and the stability suitable for high power operation is researched and the astigmatism, including the compensation in the two-rod V-shaped cavity. is also discussed.4. Theoretical research on the thermal effect of the nonlinear crystal. In the principle of mode matching and astigmatic compensation, the dynamic characteristics of the three mirror folded cavity and the astigmatism factors are analyzed through ABCD transfer matrix. By the optimization of the cavity parameters, the resonator is thermal insensitive, which controlled the astigmatism existing in the folded cavity. According to the experimental objective and the conditions available, 96W pulsed green laser is obtained by acoustic-optical Q-switched intra-cavity frequency doubling with a HGTR-KTP crystal (type II critical phase-matching). The waveform and the pulse width are measured. 5. The V-shaped cavity with dual-thermal lens is investigated theoretically through transfer matrix. The dynamic characteristics of the resonator on high power conditions is analyzed and the resonator operating in a wider range of pumping current is designed. In the experiment, two LD side-pumped modules, intra-cavity frequency doubling with a HGTR-KTP crystal (type II critical phase-matching) and dual-Q-switched technology are adopted. In the experiment, 185.21W quasi-continuous-wave (QCW) green laser is obtained when the pumping current of each diode-laser module is 21.6A, and the instability is less than 2.55% within 2 hours.The practical application of high power green laser has been studied. By using the single optical fiber coupling output technique, we adopt high damage threshold output coupling module of single fiber laser to extract the green laser out, and the output power is more than 120W. Then we applied it on the animal tissues for experiment, which provides a basis for the development of medical laser technology.
Keywords/Search Tags:Diode-side-pumped, Intra-cavity-frequency-doubling, Quasi-continuous-wave, Gain distribution, Thermal effect, Mode matching, Harmonic generation efficiency, Acoustic-optical modulation device, Q-switched
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