JILA, National Institute of Standards and Technology and University of Colorado, Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.
Phys Rev Lett. 2013 Aug 30;111(9):093604. doi: 10.1103/PhysRevLett.111.093604.
Interactions between atoms and lasers provide the potential for unprecedented control of quantum states. Fulfilling this potential requires detailed knowledge of frequency noise in optical oscillators with state-of-the-art stability. We demonstrate a technique that precisely measures the noise spectrum of an ultrastable laser using optical lattice-trapped 87Sr atoms as a quantum projection noise-limited reference. We determine the laser noise spectrum from near dc to 100 Hz via the measured fluctuations in atomic excitation, guided by a simple and robust theory model. The noise spectrum yields a 26(4) mHz linewidth at a central frequency of 429 THz, corresponding to an optical quality factor of 1.6×10(16). This approach improves upon optical heterodyne beats between two similar laser systems by providing information unique to a single laser and complements the traditionally used Allan deviation which evaluates laser performance at relatively long time scales. We use this technique to verify the reduction of resonant noise in our ultrastable laser via feedback from an optical heterodyne beat. Finally, we show that knowledge of our laser's spectrum allows us to accurately predict the laser-limited stability for optical atomic clocks.
原子与激光的相互作用为量子态的前所未有的控制提供了可能性。要实现这一潜力，需要对具有最先进稳定性的光学振荡器中的频率噪声有详细的了解。我们展示了一种使用光学晶格捕获的 87Sr 原子作为量子投影噪声限制参考来精确测量超稳激光噪声谱的技术。我们通过测量原子激发的波动，根据一个简单而稳健的理论模型，从近 dc 到 100 Hz 确定激光噪声谱。噪声谱在 429 THz 的中心频率下产生 26(4) mHz 的线宽，对应于 1.6×10(16)的光学品质因数。与两个类似激光系统之间的光学外差拍频相比，这种方法通过提供单个激光特有的信息来改进，并且补充了传统上用于评估相对较长时间尺度激光性能的 Allan 偏差。我们使用该技术通过光学外差拍频的反馈来验证我们的超稳激光中共振噪声的降低。最后，我们表明，对我们激光光谱的了解使我们能够准确预测光学原子钟的激光限制稳定性。
