The research team of Professor Zeng Heping and researcher Yan Ming from the State Key Laboratory of Precision Spectroscopy Science and Technology of East China Normal University has made important progress in infrared molecular spectroscopy measurement technology, and achieved broadband mid infrared molecular spectroscopy measurement with a spectral rate of up to 77.5Mspectra/s. The relevant results were published online on August 24, 2023, under the title "Broadband Up-Conversion Mid-Infrared Time-Stretch Spectroscopy" in the Laser&Photonics Reviews journal, and were selected as the inner cover for the current period.
There are many types of molecules in nature, each with a unique "fingerprint" characteristic spectrum. Transient molecular fingerprint spectroscopy measurement technology is the most basic tool for revealing molecular bonds and reaction processes, and is the cornerstone for promoting interdisciplinary research centered on molecules. The field of molecular science faces some important scientific challenges, such as rapidly characterizing free radical molecules in complex biochemical systems and measuring their motion patterns and reaction kinetics in real-time, which has always been an unresolved problem; For example, protein molecules have rich and complex spatial structures, and their folding changes can occur on time scales of milliseconds or even microseconds. However, there is still a lack of effective spectroscopic methods for irreversible or non repetitive physical and chemical processes. The reason is that there is a lack of broadband, high-speed, and high signal-to-noise ratio detection devices in the mid to far infrared bands where molecular fingerprint peaks are enriched.
In response to the challenge of high-speed detection of red spectra, Professor Zeng Heping's research group has proposed a new method for ultra high speed broadband infrared spectroscopy based on nonlinear frequency upconversion. A near-infrared erbium-doped fiber laser was used as the light source to obtain broadband tunable (2.6 to 3.9 μm) mid infrared femtosecond pulses using nonlinear frequency down conversion. Then, frequency up conversion technology was used to convert the broadband infrared light field to the 1.5μm band, and time-stretched Fourier spectroscopy measurement was achieved through single-mode fiber and a high-speed single point detector. The system can achieve a single spectral width of 200 cm-1, with a time of only 12.9 ns, and can continuously measure millions of independent events. Therefore, it can provide an effective transient spectral analysis method for chemical reaction kinetics, protein folding, and other research.
Figure 1: Measurement results of transient spectra of benzene during vaporization using infrared time-Fourier transform technology
Figure 2: Transient infrared spectroscopy technique for spectral measurement of benzene samples behind water layers
Source：【科研动态】宽带频率上转换时间色散傅里叶中红外光谱技术(qq.com)
Paper Link：Broadband Up-Conversion Mid-Infrared Time-Stretch Spectroscopy
