近日，德国马克斯普朗克量子光学研究所的Nathalie Picqué及其研究团队取得一项新进展。经过不懈努力，他们揭示近紫外光子计数的双梳光谱学。相关研究成果已于2024年3月6日在国际权威学术期刊《自然》上发表。

该研究团队提出一种光子计数方法，可以将该方法的独特优势扩展到非线性频率转换效率非常低的紫外区域。该研究的光谱仪基于两个重复频率略有不同的频率梳，提供原子钟精度范围内的大跨度，高分辨率频率校准，以及光谱的总体一致性。研究人员展示了量子极限下的信噪比和测量时间的最佳利用，这是由在单个光子计数器上多路记录所有光谱数据提供的。

最初的实验是在近紫外和可见光谱范围内用碱原子蒸汽进行的，每梳线的功率低至1飞瓦。这一迈向短波精确宽带光谱学的关键一步，为极紫外双梳光谱学铺平了道路，更广泛地说，为光子级诊断开辟了一个新的应用领域，例如，当驱动单个原子或分子时。

据悉，紫外光谱学提供了对物质结构的独特见解，其应用范围从基础测试到地球大气中的光化学以及太空望远镜的天文观测。在较长波长下，双梳光谱技术通过利用两个干涉激光频率梳，已成为一种功能强大的方法，能够同时实现光谱范围的广泛覆盖以及极高的分辨率。

附：英文原文

Title: Near-ultraviolet photon-counting dual-comb spectroscopy

Author: Xu, Bingxin, Chen, Zaijun, Hnsch, Theodor W., Picque, Nathalie

Issue&Volume: 2024-03-06

Abstract: Ultraviolet spectroscopy provides unique insights into the structure of matter with applications ranging from fundamental tests to photochemistry in the Earth’s atmosphere and astronomical observations from space telescopes. At longer wavelengths, dual-comb spectroscopy, using two interfering laser frequency combs, has become a powerful technique capable of simultaneously providing a broad spectral range and very high resolution. Here we demonstrate a photon-counting approach that can extend the unique advantages of this method into ultraviolet regions where nonlinear frequency conversion tends to be very inefficient. Our spectrometer, based on two frequency combs with slightly different repetition frequencies, provides a wide-span, high-resolution frequency calibration within the accuracy of an atomic clock, and overall consistency of the spectra. We demonstrate a signal-to-noise ratio at the quantum limit and an optimal use of the measurement time, provided by the multiplexed recording of all spectral data on a single photon-counter. Our initial experiments are performed in the near-ultraviolet and in the visible spectral ranges with alkali-atom vapour, with a power per comb line as low as a femtowatt. This crucial step towards precision broadband spectroscopy at short wavelengths paves the way for extreme-ultraviolet dual-comb spectroscopy, and, more generally, opens up a new realm of applications for photon-level diagnostics, as encountered, for example, when driving single atoms or molecules.

DOI: 10.1038/s41586-024-07094-9

Source: https://www.nature.com/articles/s41586-024-07094-9