In order to obtain the dual-frequency laser output with tunable frequency-difference, a design scheme of dual-frequency Nd:YAG laser with two standing-wave cavities sharing the common gain medium has been proposed, which is based on the principle of longitudinal mode selection of the Fabry-Perot etalon. Both linear and right-angle cavities including a piece of Fabry-Perot etalon, the p- and s-polarized components of the 1064nm laser will be forced to oscillate simultaneously in single longitudinal mode in the linear and right-angle cavities, respectively. As a result the orthogonally and linearly polarized dual-frequency laser at 1064nm can be output; the frequency-difference can be tuned by adjusting the tilt angles of the intra-cavity Fabry-Perot etalons, the maximum frequency-difference is predicted theoretically to approach the oscillating bandwidth of the Nd:YAG laser. The principles of single longitudinal mode selection and frequency tuning of the Fabry-Perot etalon have been analyzed, and two fused quartz-made Fabry-Perot etalons have been designed and fabricated. An experimental system of diode-pumped two-cavity dual-frequency Nd:YAG laser at 1064nm has been established, the characteristics of single longitudinal mode oscillation and frequency tuning have been investigated experimentally. The orthogonally and linearly polarized dual-frequency laser output at 1064nm has been obtained, the frequency-difference of which being 21GHz and 76GHz, respectively. Such a two-cavity dual-frequency all-solid-state laser will be widely used in the synthetic-wave absolute-distance interferometry and other fields.
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