Infrared spectroscopy is a non-intrusive method for identifying unknown samples and recognized chemical compounds. It is based on how different molecules react to infrared light. This device may have been used in airports to check for illegal narcotics. Liquid biopsy, environmental gas monitoring, contaminant identification, forensic analysis, search for exoplanets, etc., are some of the various uses of the method.

Yet the data produced by conventional infrared spectroscopy methods has low (temporal) resolution. Because collecting spectral data is a time-consuming operation, they are often only used for static samples. Multiple rapid measurements are needed to detect rapidly changing phenomena.

prof. Ideguchi and his team at the University of Tokyo have made it possible to obtain high-speed, high-resolution spectral data. The group discovered upconversion time-stretch infrared spectroscopy (UC-TSIR), which can collect 10 million spectra per second of infrared data and measure spectra with 1,000 spectral elements.

Due to the fact that the devices operate in the infrared region, where optical technology is currently limited, conventional time-stretch infrared spectroscopy data has fewer observable spectral elements (~30).

Dr Hashimoto said: “UC-TSIR breaks the limit by converting infrared pulses of molecular vibration information into near-infrared pulses with wavelength conversion (upconversion) techniques and temporarily stretching and detecting the pulses in the near-infrared region.”

“Compared to conventional methods, UC-TSIR offers more than 30 times more spectral elements and 400 times better spectral resolution. The UC-TSIR can detect high-speed phenomena, such as the combustion of gaseous molecules and irreversible chemical reactions of biomolecules, with high temporal resolution.”

“In theory, the concept sounds simple and easy to implement; but it was far from that. We carefully selected optical elements and adjusted the parameters by trial and error. Even after building the setup, we have had to deal with various spectral distortions caused by unwanted non-linear optical effects and insufficient time delay. After solving those problems, we were thrilled to finally see clear infrared absorption spectra.”

“Ultrafast continuous infrared spectral measurements at the nanosecond or microsecond scale by UC-TSIR can solve problems not solved by conventional spectroscopy methods.”

Magazine reference:

  1. Hashimoto, K., Nakamura, T., Kageyama, T. et al. Upconversion stretches infrared spectroscopy in time. Light Sci Appl 12, 48 (2023). DOI: 10.1038/s41377-023-01096-4