Single-shot broadband mid-IR spectra measured in the visible via upconversion

Sept. 5, 2013
Researchers at the Institute for Molecular Science, National Chiao Tung University, and Kagawa University have demonstrated single-shot broadband mid-IR spectroscopy using a conventional visible dispersive spectrometer.

Researchers at the Institute for Molecular Science (Okazaki, Japan), National Chiao Tung University (Hsinchu, Taiwan), and Kagawa University (Takamatsu, Japan) have demonstrated single-shot broadband mid-IR spectroscopy using a conventional visible dispersive spectrometer; they do this by chirped-pulse upconversion of broadband IR spectra into the visible region. The results (red curves) compare well to results using a conventional mid-IR Fourier spectrometer (green curves) for analyzing films of polystyrene (a) and polyvinyl alcohol (b).

The entire mid-IR spectrum from 200 to 5500 cm-1 (1.8 to 50 μm) was upconverted via four-wave difference-frequency generation (FWDFG) in xenon gas. First, a subcycle broadband mid-IR pulse was created from the fundamental and the second harmonic of a 30 fs pulse from a Ti:sapphire laser, while at the same time part of the fundamental was split off and chirped. The mid-IR pulse was passed through the medium to be analyzed; the chirped and mid-IR pulses were then combined in xenon to create a visible spectrum via FWDFG. The researchers say that the chirped-pulse upconversion method is especially applicable to mid-IR spectroscopy with attenuated total reflectance (ATR) because the temporal and spatial overlap of the mid-IR pulse and the chirped pulse would not be changed by exchanging the sample in the ATR region. Contact Takao Fuji at [email protected].

About the Author

John Wallace | Senior Technical Editor (1998-2022)

John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.

Voice your opinion!

To join the conversation, and become an exclusive member of Laser Focus World, create an account today!