High-Precision Ramsey-Comb Spectroscopy Based on High-Harmonic Generation

TL;DR

This paper demonstrates a high-precision Ramsey-comb spectroscopy technique using high-harmonic generation, achieving unprecedented accuracy in UV spectral measurements and enabling advanced tests of fundamental physics.

Contribution

The authors introduce a novel Ramsey-comb spectroscopy method based on HHG, significantly improving measurement precision in the UV range.

Findings

Achieved phase measurement precision of a few milliradians.

Enhanced the accuracy of a specific UV transition measurement by 10,000 times.

Demonstrated potential for fundamental tests with He+ spectroscopy.

Abstract

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 $5p^6 \rightarrow 5p^5 8s~^2[3/2]_1$ transition at 110 nm in $^{132}$Xe. We improve its relative accuracy $10^4$ times to a value of $2.3\times10^{-10}$. This is 3.6 times better than shown before involving HHG, and promising to enable $1S-2S$ spectroscopy of He$^+$ for fundamental tests.