Design And Research On Quadrature-demodulated Pound-drever-hall System Of Frequency Stabilization For Two-cavity Dual-frequency Solid-state Laser

The tunable two-cavity dual-frequency laser with large frequency-difference is an ideal light source for synthetic wavelength absolute distance interferometric system. In order to improve ranging accuracy of absolute distance interferometry, the synthetic wavelength must be of suitable magnitude and high stability. The magnitude of synthetic wavelength depends on the frequency difference of dual-frequency laser. In order to ensure the stability of synthetic wavelength, the frequency difference of dual-frequency laser must be stabilized highly.Therefore, it is of important scientific significance and practical value to research the frequency difference stabilization technology of dual-frequency laser.Based on summarizing the research situation of laser frequency stabilization technology,the structure features and working principle of dual cavity dual frequency solid laser are introduced in detail, and the composition and working principle of traditional PDH frequency stabilization system are introduced. An quadrature-demodulated PDH laser frequency stabilization scheme for two-cavity dual-frequency all-solid-state laser is designed. The frequency of linear cavity and that of right angle cavity are locked on two different center frequencies of the single F-P reference cavity using quadrature-demodulated PDH laser frequency stabilization technology to achieve the frequency difference stabilization.According to the disadvantages of the traditional frequency stabilization system with a phase shifter, a quadrature-demodulated PDH frequency stabilization system has been designed.In this method, the in-phase and orthogonal components of the error signal are obtained using orthogonal reference signals and PDH error is given by orthogonal phase sensitive detection.The characteristics of laser frequency discrimination and frequency tracking of quadrature-demodulated PDH method for one-cavity single-frequency solid-state laser are investigated with experimental method. The quadrature-demodulated PDH laser frequency discrimination experiment system for single-frequency solid-state laser at 1064nm is established. The linear dynamic range of 8.39MHz and sensitivity of 24.4mV/MHz are got.Important factors which limit frequency discrimination sensitivity are discussed. The frequency discrimination error signal from quadrature-demodulated PDH system is employed to adjust the length of F-P reference cavity so as to make a certain center frequency of F-P reference cavity can track that of single-frequency laser automatically. The desired laser automatic tracking experimental result is achieved and the tracking time is about 1h. The feasibility of quadrature-demodulated PDH laser frequency stabilization scheme is verified.The PDH frequency stabilization system of dual-cavity dual-frequency solid - state laser is established, and the preliminary experimentation study is carried out,these results validate the feasibility of frequency stabilization scheme.