Avalos Victor, Nie Xiaoyu, Yang Anbang, He Canming, Kumar Sunil, Dieckmann Kai
Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543.
Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542.
Rev Sci Instrum. 2023 Jun 1;94(6). doi: 10.1063/5.0152305.
We present the comparison of a field-programmable-gate-array (FPGA) based digital servo module with an analog counterpart for the purpose of laser frequency stabilization to a high-finesse optical cavity. The transfer functions of both the digital and analog modules for proportional-integral-derivative control are measured. For the lasers stabilized to the cavity, we measure the singe-sideband power spectral density of fast phase noise by means of an optical beat with filtered light transmitted through the cavity. The comparison between the digital and analog modules is performed for two low-phase-noise diode lasers at 1120 and 665 nm wavelengths. The performance of the digital servo module compares well to the analog one for the lowest attained levels of 30 mrad for the integrated phase noise and 10-3 for the relative noise power. The laser linewidth is determined to be in the sub-kHz regime, only limited by the high-finesse cavity. Our work exploits the versatility of the FPGA-based servo module (STEMlab) when used with open-source software and hardware modifications. We demonstrated that such modules are suitable candidates for remote-controlled low-phase-noise applications in the fields of laser spectroscopy and atomic, molecular, and optical physics.
我们展示了一种基于现场可编程门阵列（FPGA）的数字伺服模块与模拟对应模块的比较，目的是将激光频率稳定到一个高精细度光学腔。测量了数字和模拟模块用于比例积分微分控制的传递函数。对于稳定到该腔的激光器，我们通过与透过该腔的滤波光进行光拍频来测量快速相位噪声的单边带功率谱密度。在1120和665纳米波长的两个低相位噪声二极管激光器上对数字和模拟模块进行了比较。对于积分相位噪声最低达到30毫弧度、相对噪声功率达到10⁻³的水平，数字伺服模块的性能与模拟模块相当。激光线宽被确定处于亚千赫兹范围，仅受高精细度腔的限制。我们的工作利用了基于FPGA的伺服模块（STEMlab）在与开源软件和硬件修改一起使用时的通用性。我们证明了这种模块是激光光谱学以及原子、分子和光学物理领域中遥控低相位噪声应用的合适候选者。
