Reduction Of Residual Amplitude Modulation In Narrow Linewidth PDH Laser Frequency Stabilization Technology

In many precision research fields such as high-resolution laser spectroscopy,optical frequency comb and gravitation wave detection,lasers that have high stabilization and narrow linewidth is playing an important role.Especially in research of strontium atom optical clock,it needs the laser whose stabilization is very high and whose linewidth is as narrow as possible.Pound-Drever-Hall(PDH)laser frequency stabilization technology is one of the most effective means to acquire narrow linewidth laser,which locks the laser frequency to the resonance frequency of high finesse F-P cavity actively.This thesis focuses on the exploration and research of the mechanism of RAM,the factors affecting the magnitude and fluctuation of RAM and active RAM control.Firstly,the main principle of PDH laser frequency stabilization technology is introduced.The amplitude-frequency characteristics,phase-frequency characteristics of reflected light and the error signal of PDH are analyzed theoretically.Then the thesis discusses the technical parameters of F-P cavity and their influences on the cavity.A set of experiment system has been set up,basing on the PDH technology principles.It locks the output frequency of ECLD to the resonant peak of the F-P cavity.After that,the RAM signal monitored in the experiment and its effect on PDH laser frequency stabilization are discussed.We discussed the specific mechanism of RAM,and analyzed various parameters that have influence on magnitude and fluctuation of RAM.To verify the influence,a set of RAM signal monitoring experiment system has been set up.Which collects the RAM signals in different experimental conditions and explains the different effects.A wideband waveguide electro-optical modulator(EOM)can be driven by multiple frequencies.By synthesizing 3 RF frequencies and use these frequencies to drive the wideband waveguide EOM,3 pairs of sidebands can be added to the carrier laser frequency.The 3 sidebands on a single side of the carrier can be used to the PDH laser frequency stabilization.By adjusting the phase of one of the 3 frequencies,the baseline drift of the PDH error signal can be controlled.Here we take advantage of this character and design an active control system to compensate the baseline drift caused by the RAM of the EOM.The experiment shows that by applying the activecontrol system,the RAM can be suppressed by more than 30 dB,and the drift of the RAM is well compensated.