Hoghooghi Nazanin, Xing Sida, Chang Peter, Lesko Daniel, Lind Alexander, Rieker Greg, Diddams Scott
Precision Laser Diagnostics Laboratory, University of Colorado, Boulder, CO, 80309, USA.
Time and Frequency Division, National Institute of Standards and Technology, Boulder, CO, 80305, USA.
Light Sci Appl. 2022 Sep 7;11(1):264. doi: 10.1038/s41377-022-00947-w.
Mid-infrared (MIR) spectrometers are invaluable tools for molecular fingerprinting and hyper-spectral imaging. Among the available spectroscopic approaches, GHz MIR dual-comb absorption spectrometers have the potential to simultaneously combine the high-speed, high spectral resolution, and broad optical bandwidth needed to accurately study complex, transient events in chemistry, combustion, and microscopy. However, such a spectrometer has not yet been demonstrated due to the lack of GHz MIR frequency combs with broad and full spectral coverage. Here, we introduce the first broadband MIR frequency comb laser platform at 1 GHz repetition rate that achieves spectral coverage from 3 to 13 µm. This frequency comb is based on a commercially available 1.56 µm mode-locked laser, robust all-fiber Er amplifiers and intra-pulse difference frequency generation (IP-DFG) of few-cycle pulses in χ nonlinear crystals. When used in a dual comb spectroscopy (DCS) configuration, this source will simultaneously enable measurements with μs time resolution, 1 GHz (0.03 cm) spectral point spacing and a full bandwidth of >5 THz (>166 cm) anywhere within the MIR atmospheric windows. This represents a unique spectroscopic resource for characterizing fast and non-repetitive events that are currently inaccessible with other sources.
中红外（MIR）光谱仪是用于分子指纹识别和高光谱成像的宝贵工具。在现有的光谱方法中，吉赫兹（GHz）中红外双梳吸收光谱仪有潜力同时具备准确研究化学、燃烧和显微镜领域中复杂瞬态事件所需的高速、高光谱分辨率和宽光学带宽。然而，由于缺乏具有宽且完整光谱覆盖范围的吉赫兹中红外频率梳，这样的光谱仪尚未得到验证。在此，我们介绍首个重复频率为1 GHz的宽带中红外频率梳激光平台，其光谱覆盖范围为3至13 µm。该频率梳基于商用的1.56 µm锁模激光器、坚固的全光纤铒放大器以及在χ非线性晶体中对少周期脉冲进行的脉冲内差频产生（IP-DFG）。当用于双梳光谱（DCS）配置时，该光源将能够在中红外大气窗口内的任何位置同时实现具有微秒时间分辨率、1 GHz（0.03 cm）光谱点间距和大于5 THz（大于166 cm）全带宽的测量。这代表了一种独特的光谱资源，可用于表征目前其他光源无法实现的快速且非重复的事件。
