Design Of Frequency Stabilizing System For Two-cavity Dual-frequency Nd:YAG Laser Using Fabry-Perot Etalon As Mode Selector

Laser is characterized by good monochromaticity,good coherence and good directionality,it plays an extremely important role in many fields such as industry,national defense and science and technology,especially in the field of laser precision measurement applications.With the measurement accuracy being required,the stability of the laser frequency is getting higher and higher.But the resonance frequency of the laser is easily drifted by the external environment,which affects the accuracy of the laser measurement.Therefore,active frequency stabilization measures must be taken to ensure the high stability of the laser frequency.In this thesis,the two-cavity dual-frequency Nd:YAG laser with two intra-cavity Fabry-Perot etalons is taken as a frequency-stabilization object,and a dual-frequency laser frequency-stabilization system has been design using both intra-cavity Fabry-Perot etalons as frequency-stabilization references,which has important research value and broad application prospects.The main content of this thesis includes the following three parts:Firstly,the research status of laser frequency stabilization technology has been reviewed,and the composition and working principle of a two-cavity dual-frequency Nd:YAG laser system using the Fabry-Perot etalon as laser mode selector have been introduced.Based on the analysis of commonly used laser frequency stabilization methods,a frequency stabilization scheme for the two-cavity dual-frequency Nd:YAG laser acting Fabry-Perot etalon as mode-selector has been proposed,that is,the transmission peak resonance frequency of the Fabry-Perot etalon within the laser cavity as a reference frequency,a small amplitude audio sinusoidal jitter signal is applied to the piezoelectric ceramic tube(PZT)on the laser cavity mirror to cause a small sinusoidal periodic jitter of the laser cavity length,thereby causing a sinusoidal modulation of the laser output power.When the modulation frequency of the laser output power is twice the frequency of the external jitter signal,the laser frequency is just at the resonance frequency of the Fabry-Perot etalon transmission peak,and the laser is in a stable state of frequency lock-in;When the laser output power modulation signal is at the same frequency as the external jitter signal,the laser frequency is located at the left or right of the transmission peak resonance frequency of the Fabry-Perot etalon,and the position of the laser cavity mirror is feedback through the designed frequency stabilization controlling circuits to adjust the laser frequency onto the resonance frequency of the Fabry-Perot etalon transmission peak.By designing two independent laser frequency stabilization control systems and simultaneously stabilizing the resonance frequency of the linear cavity and the right-angle cavity Nd:YAG laser,the frequency stability of the dual cavity dual frequency Nd:YAG laser can be achieved.Secondly,a hardware circuit system for frequency stability of the two-cavity dual-frequency Nd:YAG laser has been designed,which mainly includes a photoelectric conversion circuit;an adjustable DC voltage source,a DDS signal generator,an amplifier circuit,a frequency selection circuit,a phase sensitive detection circuit and a low-pass filter circuit.The laser output optical signal can be converted into an electrical signal throng a photo-electric conversion circuit;the adjustable DC voltage source makes the laser frequency within the transmission peak bandwidth of the Fabry-Perot etalon;the signal generator generates two signals with the same frequency,one is added as a modulation signal to the laser,and the other is used as a reference signal in phase sensitive detection;the amplifier circuit amplifies the laser output power modulation signal;the frequency selection circuit filters out the laser output power signal whose modulation frequency is twice the frequency of the external jitter signal;the phase sensitive detection circuit multiplies the laser output power modulation signal and the jitter signal;low-pass filtering circuit outputs a DC signal after the phase sensitive detection process.The characteristics of each unit circuit have been simulated and analyzed using the Multisim software.Thirdly,using 1064nm single frequency Nd:YAG laser as the light source,an experimental system has been designed and established to verify the feasibility of the laser frequency stabilization circuit system designed in this thesis.The verification experiment results show that the laser frequency stabilization unit circuits designed in this thesis are feasible,which lays a solid foundation for further research on the frequency stabilization technology of the two-cavity dual-frequency Nd:YAG laser.