Ozawa Akira, Davila-Rodriguez Josue, Bounds James R, Schuessler Hans A, Hänsch Theodor W, Udem Thomas
Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, 85748, Garching, Germany.
National Institute of Standards and Technology (NIST), 325 Broadway, Boulder, 80305, CO, USA.
Nat Commun. 2017 Jun 29;8(1):44. doi: 10.1038/s41467-017-00067-9.
Optical frequency combs have revolutionized the measurement of optical frequencies and improved the precision of spectroscopic experiments. Besides their importance as a frequency-measuring ruler, the frequency combs themselves can excite target transitions (direct frequency comb spectroscopy). The direct frequency comb spectroscopy may extend the optical frequency metrology into spectral regions unreachable by continuous wave lasers. In high precision spectroscopy, atoms/ions/molecules trapped in place have been often used as a target to minimize systematic effects. Here, we demonstrate direct frequency comb spectroscopy of single Mg ions confined in a Paul trap, at deep-UV wavelengths. Only one mode out of about 20,000 can be resonant at a time. Even then we can detect the induced fluorescence with a spatially resolving single photon camera, allowing us to determine the absolute transition frequency. The demonstration shows that the direct frequency comb spectroscopy is an important tool for frequency metrology for shorter wavelengths where continuous wave lasers are unavailable.Frequency combs are useful tools in high precision measurement including atomic transitions and atomic clocks. Here the authors demonstrate direct frequency comb spectroscopy to shorter wavelengths by probing a transition frequency in a trapped Mg+ ion using a single mode of a UV frequency comb.
光学频率梳彻底改变了光频测量方式，提高了光谱实验的精度。除了作为频率测量标尺的重要性之外，频率梳本身还能激发目标跃迁（直接频率梳光谱学）。直接频率梳光谱学可能会将光频计量扩展到连续波激光器无法到达的光谱区域。在高精度光谱学中，被囚禁在特定位置的原子/离子/分子常被用作目标，以尽量减少系统效应。在此，我们展示了在深紫外波长下对囚禁在保罗阱中的单个镁离子进行直接频率梳光谱学研究。一次大约20000个模式中只有一个模式能发生共振。即便如此，我们仍能用空间分辨单光子相机检测到诱导荧光，从而确定绝对跃迁频率。该演示表明，直接频率梳光谱学是在连续波激光器无法使用的较短波长下进行频率计量的重要工具。频率梳是高精度测量中的有用工具，包括原子跃迁和原子钟。本文作者通过使用紫外频率梳的一个单模探测囚禁镁离子中的跃迁频率，展示了直接频率梳光谱学在更短波长下的应用。
