| RTP electro-optic crystal is a novel electro-optic material and is suitable for use as modulator in high frequency field. RTP has many excellent characteristics such as large electro-optic coefficients, high damage threshold, good chemical stability, high resistivity, low piezo-electric effect and non-hygroscopicity etc. It can thus be utilized in electro-optic modulation, pulse shaping and intracavity Q-switching in laser cavity. The traditional electro-optic crystals such as LN and DKDP are not applied for high rep rate situation because of their self-limitation, but novel electro-optic crystal RTP can be easily operated in high frequency range. Compared with BBO crystal which also can be used as high rep rate modulator, RTP switch needs lower half-wave or quarter-wave voltage so as to decrease the costs of producing high frequency and high voltage driver. Compared with KTP crystal which is an isomorphic compound of RTP crystal, RTP can be produced by skilled method which can break the obstacle of low resistivity of KTP.However now, there are few reports on RTP Q-switched solid laser and even fewer papers published on the developments of RTP electro-optic switches in high rep rate region.In this thesis, it begins with the analyses of extinction ratio of RTP switch, then gives the experimental results and theoretical analyses of the characteristics of RTP Q-switching Nd:YAG laser and finally shows the performance of RTP Q-switching KTP frequtncy-doubling Nd:YAG laser.The main contents are as following:(1) The thesis analyses the principal factors that obviously impact the extinction ratio of electro-optic switch structured with double crystals. By adopting refractivity ellipsoid method, the angles between the incident light passing through crystals and the crystal x axes, the directions of the applied electric fields on z axes of double crystals, the angles between the x axes of double crystals and the polarization direction of polarizers all of which probably have important effects on the extinction ratio of the E-0 Q-switch were considered. It is finally found that the effects of the directions of the x axes of double crystals and the polarization directions of polarizers on extinction ratio are more obvious. The results will be useful to precisely assemble and fast adjust the electro-optic switch.(2) With different transmits of output mirror, the output properties of RTP Q-switched YAG laser is obtained and the experimental results are compared between RTP Q-switched laser and LN Q-switched laser. It concludes that the performance of RTP Q-switched laser is obviously better than that of LN Q-switched. The plane wave approximate rate-equation is adopted to numerically calculate the output properties of RTP Q-switched laser and the analyses are well according with the experimental results.(3) The output properties of RTP Q-switched KTP frequency-doubling Nd:YAG laser are totally measured. The properties of green light of RTP Q-switched KTP frequency-doubling laser and those of acousto-optic Q-switched KTP frequency-doubling laser are also compared and it concludes that RTP Q-switched KTP frequency-doubling laser works better. The rate-equations suitable for electro-optic Q-switched frequency-doubling are also given and the analytical conclusions are well in accordance with experimental results.The main creative points of this thesis are:(1) At the first time, the analyses of effects of factors on extinction ratio of double crystal switch are given. This can be very useful to precisely assemble and fast adjust the electro-optical switch with double crystals.(2) The run of RTP Q-switched YAG laser with flash-lamp pumping is realized. It can be tunable in a large frequency range from 14KHz to 50KHz.(3) The run of RTP Q-switched KTP frequency-doubling YAG laser is also realized. The main performances of the above laser are superior to acousto-optic Q-switched frequency-doubling laser. |
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