Design And Experimental Research Of Orthogonal Demodulation PDH Frequency Stabilization System For Two-cavity Dual-frequency All-solid-state Laser

Due to its wide tuning range and large frequency difference,the dual-cavity dual-frequency all-solid-state laser is often used as an ideal light source for synthetic wave absolute distance interferometry measurement systems.The synthetic wave absolute distance measurement system requires that the synthetic wavelength has an appropriate magnitude,and the stability of the synthetic wavelength directly determines the measurement accuracy.If you want to obtain a highly stable synthetic wavelength,you need to ensure the stability of the dual-frequency laser frequency difference.Therefore,studying the frequency difference stability of dual-frequency solid-state lasers is of great significance in the field of absolute distance measurement of synthetic waves.With the review of the current development of laser frequency stabilization technology,this paper analyzes the sysytem composition and operating characteristics of single-and double-cavity solid-state lasers based on F-P standard with mode selection principle,and also the generating principle of dual-frequency laser.Several currently used methods of actively making frequency stable are introduced here with their advantages and disadvantages.The essay theoretically introduces the Pound-Drever-Hall(PDH)frequency stabilization method and its working principle based on f-P cavity reflection characteristics and obtains the PDH frequency stabilization and discrimination curve through simulation.Considering the shortcomings of using the phase shifter to realize the phase matching of the reference signal and the laser output signal in the traditional PDH frequency stabilization method,this paper intoduces a PDH frequency stabilization system without phase shifter for the dual-cavity dual-frequency all-solid-state laser based on orthogonal demodulation principle.Each unit circuit module of the frequency stabilization system is intoduced here,mainly including frequency selection amplifier circuit,mixing circuit,filter circuit,and DDS signal generator and A/D acquisition module.The feasibility of each circuit module is analyzed through simulation and the PCB circuit board for each module is designed through EDAThe thesis establishes an PDH frequency stabilization experimental system with orthogonal demodulation for the dual-cavity dual-frequency all-solid-state laser,respectively studying the frequency discrimination characteristics and frequency locking characteristics of the system.Experiments entail the double-cavity PDH frequency-stabilized dispersion-type frequency discrimination curve.By analyzing and calculating the frequency discrimination curve,the frequency variation range and the frequency discrimination sensitivity of the linear cavity are respectively 8.68MHz and 25.6mV/MHz,and those of the right-angle cavity are respectively 8.42MHz and 24.2mV/MHz.Based on the experimental study of the frequency discrimination characteristics,the frequency error signals of the linear cavity and the right-angle cavity are superimposed on the PZT driving voltage of the corresponding laser cavity mirror,and the cavity lengths of the linear cavity and the right-angle cavity are feedback adjusted,so that the resonant frequencies of the linear cavity and the right angle cavity are locked at two different resonant frequencies of the FP reference cavity.Under the existing experimental conditions,if the frequency lock duration exceeds 30 minutes,the corresponding maximum frequency changes of the linear cavity and the right-angle cavity are 3.9 MHz and 4.1 MHz,respectively.