LaserLaB, Department of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, Netherlands.
Phys Rev Lett. 2019 Oct 4;123(14):143001. doi: 10.1103/PhysRevLett.123.143001.
High-harmonic generation (HHG) is widely used for up-conversion of amplified (near) infrared ultrafast laser pulses to short wavelengths. We demonstrate that Ramsey-comb spectroscopy, based on two such pulses derived from a frequency-comb laser, enables us to observe phase effects in this process with a few mrad precision. As a result, we could perform the most accurate spectroscopic measurement based on light from HHG, illustrated with a determination of the 5p^{6}→5p^{5}8s^{2}[3/2]_{1} transition at 110 nm in ^{132}Xe. We improve its relative accuracy 10^{4} times to a value of 2.3×10^{-10}. This is 3.6 times better than shown before involving HHG, and promising to enable 1S-2S spectroscopy of He^{+} for fundamental tests.
高次谐波产生（HHG）被广泛用于将放大的（近）红外超快激光脉冲转换为短波长。我们证明，基于两个源自频率梳激光的此类脉冲的拉姆齐组合光谱学使我们能够以几毫弧度的精度观察该过程中的相位效应。结果，我们可以基于 HHG 光进行最精确的光谱测量，用在 ^{132}Xe 中 110nm 处的 5p^{6}→5p^{5}8s^{2}[3/2]_{1}跃迁的确定来说明，其相对精度提高了 10^{4}倍，达到 2.3×10^{-10}。这比以前涉及 HHG 的结果好 3.6 倍，有望使 He^{+}的 1S-2S 光谱学用于基础测试。
