| Dual-frequency laser plays an especially important role in many fields such as optical sensing and optical heterodyne interferometry, etc, greatly accelerated the industrial production and technological progress. Currently, the dual-frequency lasers mainly used are He-Ne gas lasers, including 632.8nm dual-frequency He-Ne laser based on the Longitudinal Zeeman effect and birefringence, and 632.8nm double longitudinal modes He-Ne laser. Due to the gain line width limit of the Ne atom, these dual-frequency He-Ne lasers'frequency difference are generally small, the maximum frequency difference are less than 1.2GHz, greatly limiting the application range of dual-frequency laser. In the absolute distance interferometry, a large frequency difference dual frequency laser whose frequency difference is up to several GHz, tens of GHz and above is needed as the light source, therefore the investigation of the dual-frequency laser with large frequency-difference is of great significance.In this thesis, based on the analysis of coupled-cavity mode selection principle, apply the laser longitudinal mode splitting technique, a laser diode (LD) end-pumped dual-frequency Nd:YAG laser research program has been designed, and its feasibility has been experimentally verified. The main contents of this thesis are included as follows.Firstly, the application, research progress and developing trends of dual-frequency laser have been sketched. The principle, configeration and key technologies of LD-pumped solid-state laser have been briefly description and the basic characteristics of the lasers have been analyzed.Subsequently, variety of commonly used mode selection theory has been introduced, the coupled-cavity mode selection principle and the oscillation condition of coupled-cavity laser have been mainly studied, the results shown that the cavity length is enforced to satisfy with the self-consistent formula and as the same time the value of G reaches the lowest value, the laser system can realize output of single-frequency laser. The mode selection characteristics have been simulated by MATLAB, the results suggested that coupled-cavity can realize mode selection and the spacing of the oscillating modes is equal to the spacing of the interval cavity modes.Thirdly, An experimental system of single-frequency Nd:YAG laser system which is based on coupled-cavity mode-selection principle has been designed, and the characteristics of mode selection and the wave-length turning have been experimentally studied. The results indicated that only the laser system whose cavity length meets the coupled-cavity laser oscillation conditions can realize single-mode output.Finally, On the basis of analyzing the mode splitting principles and techniques, two birefringence dual-frequency Nd:YAG lasers with stable and Tunable frequency difference based on coupled-cavity mode-selection principle have been designed, and the feasibility of the two systems have been analyzed. A LD end-pumped birefringence 1064nm dual-frequency Nd:YAG laser based on coupled-cavity mode-selection principle experimental system has been established and the oscillating characteristics of the stable frequency difference dual-frequency Nd:YAG laser has been studied experimentally, the results suggested that when the cavity length of Nd:YAG laser is 39mm and only a calcite plat whose thickness is 3mm is in the laser cavity. It had been observed experimentally that the frequency difference of the orthogonally and linearly polarized dual-frequency laser at 1064nm was about 937MHz.Compared with the dual-frequency He-Ne laser, the birefringence dual-frequency Nd:YAG laser based on coupled-cavity mode-selection principle which proposed in this thesis have many advantages such as large frequency difference, simple structure and small size, etc, which has a broad prospect of application. |
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