| A tunable diode laser with single mode and narrow linewidth is widely used in atom-cooling, pumping atomic, exciting atomic fluorescence and so on. The application of semiconductor diode laser is a new feature of new atomic clocks. Develop a robust external cavity diode laser (ECDL) is a key to assure atomic clocks especially space atomic clocks can run stably for a long period. This laser is insensitive to mechanical vibration and can give a warning signal when frequency of the laser is out of range, then relocked again.With the development and popularization of computer technology, the Virtual Instrument(VI) based on computer is applied more and more widely. The automatic digital frequency locking system with VI is presented in this paper. First, The principle of frequency stabilization of semiconductor is introduced. Then, we designed and realized a system to make the laser locked to the frequency of Cs atom absorption spectrum by PI feedback control. The strict research about all units of the ECDL automatic digital frequency locking system is presented in the paper. The entire system can be divided into several modules: temperature control module, data acquisition module, software interface module, data processing units. These units have been subdivided into single function parts, which are designed and tested respectively.We had tested the system with the ECDL. The result is that our system could lock the output frequency of the laser to the frequency of the any Cs absorption spectrum peak automatically and relock it quickly when the frequency of the laser is out of range. Moreover, it has ability of anti-inference and good performance of long time stability. Finally, the main factors which influence the precision of the system are analyzed in detail in this paper.This system has characters of good transformation and friendly human-machine interface. Meanwhile, it's convenient to operate panel and modify parameter. Now, it has been used in the research of Cs atomic fountain clock. |
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