Study Of LD-Pumped Dual-Frequency Nd:YAG Laser Technique

Dual-frequency laser plays an extremely important role in absolute-distance interferometry. Because this measurement approach measures the distance rather than the displacement, it doesn't need precise guide rail, but in order to improve the accuracy of absolute-distance measurement, smaller synthetic wavelength is required, which can be obtained by use of a dual-frequency laser source with its frequency-difference as large as possible. As a result, investigating the dual-frequency laser technique is of great significance.A laser-diode (LD) end-pumped dual-frequency Nd:YAG laser technique is analyzed theoretically and investigated experimentally, and a novel scheme of large frequency-difference dual-frequency laser is designed and verified. Main contents of this thesis are included as follows.First, the theory of LD-pumped solid-state laser (DPSSL) is analyzed. By means of the rate equation of four-energy-level solid-state laser system, the DPSSL operating characteristics are analyzed theoretically and investigated. The corresponding DPSSL experimental system is established and its output characteristics are investigated.Secondly, the continuous-wave operating theory of the frequency-doubled laser is analyzed. The problem of phase-matching in KTP frequency-doubling crystal is discussed. The type-II critical phase-matching requires that the polarization directions of the fundamental waves be mutually perpendicular, and the frequency-doubling efficiency reaches the maximum when the magnitudes of both components of the fundamental waves are equal.Thirdly, the designed scheme of dual-frequency Nd:YAG laser is optimized, and a compact laser configuration is obtained. The single-frequency laser output is realized by means of the longitudinal mode selection property of the birefringent filter. The green laser beams can be output from the two cavities by changing the angel between the f component of KTP and the p component of the PBS element.Lastly, the scheme of laser frequency stabilization is designed. The relationship between sensitivity and modulation frequency is discussed by application of the F-P optical heterodyne spectrum theory, and the numerical simulation is carried out by use of the Matlab software.