Picqué Nathalie, Hänsch Theodor W
Max-Planck Institute of Quantum Optics, 85748 Garching, Germany;
Faculty of Physics, Ludwig-Maximilian University of Munich, 80799 Munich, Germany.
Proc Natl Acad Sci U S A. 2020 Oct 27;117(43):26688-26691. doi: 10.1073/pnas.2010878117. Epub 2020 Oct 14.
We probe complex optical spectra at high resolution over a broad span in almost complete darkness. Using a single photon-counting detector at light power levels that are a billion times weaker than commonly employed, we observe interferences in the counting statistics with two separate mode-locked femtosecond lasers of slightly different repetition frequencies, each emitting a comb of evenly spaced spectral lines over a wide spectral span. Unique advantages of the emerging technique of dual-comb spectroscopy, such as multiplex data acquisition with many comb lines, potential very high resolution, and calibration of the frequency scale with an atomic clock, can thus be maintained for scenarios where only few detectable photons can be expected. Prospects include spectroscopy of weak scattered light over long distances, fluorescence spectroscopy of single trapped atoms or molecules, or studies in the extreme-ultraviolet or even soft-X-ray region with comb sources of low photon yield. Our approach defies intuitive interpretations in a picture of photons that exist before detection.
我们在几乎完全黑暗的环境中，以高分辨率探测宽频谱范围内的复杂光谱。使用单光子计数探测器，探测的光功率水平比常用水平弱十亿倍，我们观察到计数统计中的干涉现象，该干涉由两台重复频率略有不同的独立锁模飞秒激光器产生，每台激光器在宽光谱范围内发射一组均匀间隔的谱线梳。因此，在预期只能检测到少量光子的情况下，双梳光谱这一新兴技术的独特优势，如利用多条谱线进行多路数据采集、潜在的超高分辨率以及用原子钟校准频率标度等，仍然能够得以保持。其应用前景包括长距离弱散射光光谱学、单个捕获原子或分子的荧光光谱学，或者利用低光子产额的梳状光源在极紫外甚至软X射线区域进行的研究。我们的方法在检测前光子存在的图景中违背了直观的解释。
