Software Design Of A Saturation Spectrum Frequency-stabilization System For DFB Lasers

With the rapid development of optoelectronic technology,semiconductor lasers,as one of the most important and widely used light sources,are increasingly demanded in various fields such as scientific research,industrial production and medical clinical applications.This thesis proposes a design of a frequency-stabilization system for semiconductor lasers that are susceptible to frequency drift due to ambient temperature and operating current.This thesis investigates the design of a frequency-stabilization system.Based on the theory of frequency stabilization of the saturated absorption spectrum,a complete system capable of achieving frequency stabilization of the output of an 852nm DFB（Distributed Feedback Laser）semiconductor laser is designed.The main research elements of the thesis include:Firstly,the thesis starts with an introduction to the absorption properties of light and then analyses the natural linewidth and Doppler spreading caused by the absorption effect of light.Because it is difficult to observe the natural linewidth against the Doppler background,the technique of saturated absorption spectroscopy is proposed,which removes the Doppler background from the saturated absorption spectrum and thus allows one to observe precise absorption spectral lines close to the natural linewidth.This technique can provide a precise and stable reference frequency for the implementation of laser frequency stabilization systems.Based on the above theory,the thesis details the principles of the implementation of the frequency-stabilization system,including the acquisition of the saturated absorption spectrum signal with the Doppler background removed,the extraction of the error signal in the feedback control of the frequency stabilization system,and the basic principles of the feedback control and the adjustment of the optimum parameters.Secondly,the whole scheme design of the frequency stabilization system is introduced,including the design and implementation of the optical experiment system in the frequency stabilization system,the design in the hardware circuit system and the design of the application software system,where the design part of the application software system focuses on the embedded development application part of the frequency stabilization system,including the design of the underlying firmware program and the design of the upper layer interactive interface.Thirdly,the human-computer interface is designed using the LABVIEW environment for graphical programming.Under the general design architecture of the TCP client,the parameter command package is designed to facilitate the transmission of user-issued commands in conjunction with the experimental requirements,to realize the real-time display of the saturation absorption spectrum and error signal on the PC,and to control the conditioning circuit part of the DFB semiconductor laser to perform relevant operations including voltage scanning,modulation and demodulation,low-pass filtering and PID calculation after the user has given control commands to achieve the final frequency stabilization.Next,the LABVIEW development environment is used for graphical programming to realize the design of the upper interactive interface.On the premise of establishing the architecture of the TCP client,a human-machine friendly user interface is designed in conjunction with the overall requirements of the frequency stabilization system,which can realize the real-time display and storage of the saturated absorption spectrum signal and the extracted error signal detected by the system on the user’s computer,and when the user issues a When the user gives a control command,the hardware circuitry of the laser can be fed back to make changes,such as setting the voltage sweep range,adjusting the modulation signal and calculating the PID of the error signal.Based on the design of each module,a completed frequency-stabilization system was integrated and tested on the 852nm DFB semiconductor laser,achieving an output frequency stability of 9.4×10 ^9-in the short term and 1.45×10^8-in the long term,confirming the feasibility of the whole system design.Finally,the overall research work on the design of a saturated absorption spectrum frequency-stabilization system is summarized and the shortcomings and areas for improvement are presented.At the same time,future research on frequency-stabilization systems is presented.