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Research Of Nanosecond Cr,Tm,Ho:YAG Laser

Posted on:2013-06-07Degree:MasterType:Thesis
Country:ChinaCandidate:J YangFull Text:PDF
GTID:2268330398490623Subject:Optical Engineering
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The2μm laser has been widely used in atmospheric detection, rangefinders and high precision surgery for its merits such as being safe to human’s eye, being absorbed by water sorely and being transferred by fiber with less-OH. Surgery with higher precision and broader detection range require higher pulse energy and narrower pulse duration of laser. Q-switch is widely used to obtain huge pulse. The electro-optic(EO) Q-switch can switch quickly, be made smaller, and have higher precision of control, which make it have a huge practical potential. This paper is to solve the problems in EO Q-switch of2μm and manufacture an EO Q-switched Cr,Tm,Ho:YAG laser with high pulse energy and narrow pulse duration. Specifically, we carried out study as follows:Proceeding from theory of energy stage,the energy transmitting process of Cr3+'Tm3+'Ho3+was analyzed. The rate equation of the crystal was set up. The best proportion of the three ions in Cr,Tm,Ho:YAG laser was analyzed.Proceeding from temperature distribution in the laser rod and thermal stress, the temperature distribution in the laser Cr,Tm,Ho:YAG rod pumped by high energy lamp was analyzed. The mechanism of thermal introduced birefringence was studied. Several means for compensating depolarization were introduced. The calculating formula of depolarization degree was derived. The distribution of the depolarization in the face of the crystal was stimulated by using Matlab. The depolarization of the laser system before and after the insertion of λ/4plate were calculated. The result derived by theory calculating was consistent with the experimental result.The problems and resolvents of EO Q-switched Cr,Tm,Ho:YAG laser were discussed and the experimental platform was built based on that. Appropriate EO crystal was chosen, the transmissivity of the output mirror was optimized and the depolarization of the crystal was compensated. The laser pulse with pulse energy of443mJ and pulse duration of90ns was obtained at the temperature of22°, the pump energy of200J and the frequency of3Hz.
Keywords/Search Tags:High energy, Electro-optical Q-switch, Cr,Tm,Ho:YAG, Compensationof thermal-induced depolarization
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