Two-cavity dual-frequency Nd:YAG laser based on the principle of longitudinal mode selection by Fabry–Perot etalon

To obtain the dual-frequency laser output with large and 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 principles of polarization splitting and single longitudinal mode selection of intracavity Fabry–Perot etalon. With each of the cavities containing a piece of Fabry–Perot etalon, the p- and s-polarized components of the laser at 1064 nm 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 1064 nm can be obtained. The principle of single longitudinal mode selection by use of the Fabry–Perot etalon has been analyzed, and the Fabry–Perot etalons have been designed. An experimental system of the two-cavity dual-frequency Nd:YAG laser at 1064 nm has been established, and the characteristics of single longitudinal mode oscillation of the two cavities have been investigated experimentally. The orthogonally and linearly polarized dual-frequency laser output at 1064 nm has been obtained; the main characteristics of the oscillating threshold and output power, the polarization state as well as the laser beam quality have been tested experimentally. The frequency difference of the dual-frequency laser has been tuned in turn to 16, 24, 37, and 76 GHz, by slightly adjusting the tilt angles of the intracavity Fabry–Perot etalons. Such a two-cavity dual-frequency Nd:YAG laser will be widely used in the synthetic-wave absolute-distance interferometry and other fields.