ObjectiveThe narrow-linewidth, continuously tunable single-frequency 319 nm ultra-violet laser system is of great significance for the single-step Rydberg excitation of cesium atoms. The use of high-precision ultra-stable optical cavity, combined with PDH (Pound-Drever-Hall) frequency stabilization technology, electronic sideband frequency stabilization technology, and HC (Hansch-Couillaud) frequency stabilization technology, which realize the frequency locking of the single-frequency ultraviolet laser system. However, the structure of the conventional feedback locking system is much complex, the cost is higher, the volume is larger, and the whole process requires more seperated instruments. Therefore, FPGA (Field Programmable Gate Array) is used to simplify and upgrade conventional feedback locking systems.MethodsFPFA has the advantages of low energy consumption, high efficiency, high flexibility, high integration, high stability, programmability, and it has application prospects in the whole scientific research, especially in the field of quantum optics and atomic physics. Frequency sweeping, modulation and demodulation, feedback control and monitoring through the Red Pitaya board can make the whole laser system simple. FPGA can not only greatly reduce the cost in the experiment, but also fully save the space, bring great convenience, and have high integration, high flexibility, high stability and simple operation.Results and DiscussionsBased on the Red Pitaya's FPGA board, the laser frequency is locked by using PDH frequency stabilization technology, electronic sideband frequency stabilization technology, and HC frequency stabilization technology. The frequency locking effect of PDH frequency stabilization technology and HC frequency stabilization technology of the four-mirror frequency-doubling ring cavity is compared, the frequency fluctuation after PDH locking is ±0.425 MHz within 10 minutes, and the frequency fluctuation after HC locking is ±0.61 MHz within 10 minutes, the locking effect of PDH scheme is better, and it has a wider range of continuous frequency scanning.ConclusionThe laser frequency locking of the entire 319 nm ultra-violet laser system is realized based on FPGAs. the frequency sweeping, modulation and demodulation, feedback control, and monitoring can be realized through FPGA, and the IQ module, ASG module, PID module, Switch module, and Scope module in FPGA board are used to replace the conventional seperated equipments. Based on the Red Pitaya's FPGA board, PDH locking technology and electronic sideband locking technology are used to achieve 1560 nm and 1077 nm laser frequency locking at the same time; and the frequency locking effect of PDH locking technology and HC locking technology on the four-mirror frequency-doubling ring cavity was compared. FPGA realizes the simplification of the entire laser system, which can not only save space and cost, but also has excellent performance, improves the integration of the system, reduces the complexity of instrument operation, and is easier to operate.