基于DDS的激光频率高精度控制系统及其应用

High-accuracy control system based on DDS for laser frequency and its applications

在诸如激光冷却原子、光频标和冷原子干涉等实验中,通常采用压控振荡器(VCO)技术对激光移频,但是移频精度和稳定性不能满足实验要求。本文提出并研制了一种直接数字频率合成器(DDS)及其专用高精度时序控制系统用于激光的移频。DDS基于AD9852芯片,配合微控制器(MCU)控制其参数,输出经功率放大后直接驱动声光调制器以调控激光频率。上位计算机端的专用控制系统采用Labview平台结合高精度数据采集卡,以精确地调控时序。经测试,系统产生的信号相噪低、线宽窄于5Hz、谐波抑制比优于30dB、频率精度优于10-7和时序调控精度优于1μs,且参数调节方便、控制界面友好,这一系统已成功地应用在激光冷却原子和原子喷泉实验中。

In many experiments such as laser cooling of atoms, optical frequency standard and atomic interferometer,the voltage controlled oscillator （VCO） was usually used to shift laser frequency in the past,but its accuracy and stability could not satisfy the demands of the experiments. In this paper, we have demonstrated a direct digital synthesizer （DDS）. It can be used in high-accuracy control system for laser frequency shift. This DDS is based on IC AD9852 and micro control unit （MCU）. Its amplified out- put can drive the acoustic optical modulator （AOM） directly to shift laser frequency. The Labview con- trol system operates on supervisory computer and controls the timing sequence accurately. Testing re- sults demonstrate that the signal generated by this device has low phase noise, narrow bandwidth below 5 Hz,high harmonic suppressing ratio higher than 30 dB,high frequency accuracy better than 10-7 and high timing accuracy shorter than 1μs. The control system has the friendly user interface. It has been used successfully for laser cooling of atoms and atomic fountain.