Study On Quadrature Democdulation Pound-drever-hall Techniques Of Frequency Stabilization For Single-frequency Solid-state Laser

Lasers have been widely used in many fields such as information sensing and measurement,etc,especially the laser wavelength used as a length reference can reappear the definition of a meter,in this case the laser frequency is required very stable,but due to the outside perturbs,the laser frequency is shifted,as affects the accuracy of measurement.Therefore the research on laser frequency stabilization technology is of great significance.In this thesis,based on the traditional.Pound-Drever-Hall(PDH)laser frequency stabilization method,a quadrature demodulation method for PDH frequency stabilization is designed for a single-frequency solid-state laser.And some experimental studies have been performed.The main research contents are included as follows.The composition and operating principle of traditional PDH frequency stabilization system have been briefly described.The disadvantages of the frequency stabilization system with a phase shifter have been analyzed.Based on the principle of quadrature demodulation,a PDH frequency stabilization system has been designed,which uses a direct digital frequency synthesizer(DDS)and two reference signal of sine and cosine with a frequency of 10MHz,the sine signal is not only used as a reference of the mixer,but also as an external signal to drive the electro-optical modulator(EOM).The single-frequency laser beam has been phase modulated and coupled to the reference Fabry-Perot cavity,the optical heterodyne interference signal is detected by a photo detector,the output signal is mixed with both quadrature reference signals and then low-pass filled,as a result,both orthogonal compolents of the error signal have been obtained.Both components have been A/D converted and then sent into a PC to perform the operation of orthogonal phase sensitive detection,an error signal of the PDH frequency stabilization system can be obtained.Using a PID control system,the error signal is fedback to adjust of the cavity length of the single-frequency solid-state laser,locking the laser frequency in the resonant frequency of the Fabry-Perot cavity.The scheme uses the same DDS component to generate both reference signals,which guarantees the amplitude consistency and the phase orthogonality of both reference signals.The effects of residual amplitude modulation,laser amplitude noise,mode matching and other factors on the frequency stabilization have been analyzed,and the orthogonal demodulation circuits have been also designed.The PDH frequency stabilization system for the 1064nm single-frequency solid-state laser has been established,and the single-frequency laser has been phase-modulated.By linearly scanning the cavity-length of the Fabry-Perot reference cavity,the expected frequency discrimination curve has been observed experimentally.The maximum frequency variation of the error signal is 5.48MHz,and the frequency discrimination sensitivity is 1.82V/MHz.The output voltage error signal of the quadrature demodulation PDH frequency stabilization system being processed,the cavity-length of the Fabry-Perot reference cavity has been fedback to be adjusted so as to track the laser frequency change.The experimental results have shown that the scheme orthogonal demodulation PDH frequency stabilization is feasible.In a word,the PDH frequency stabilization techniques have been deeply studied in this thesis,the designed quadrature demodulation PDH frequency stabilization system can be used in the laser frequency stabilization,as has laid a solid foundation for the further study of the PDH frequency stabilization for single-frequency solid-state lasers and frequency-difference stabilization for double-cavity dual-frequency solid-laser with large frequency-difference.