  Vibrational spectroscopy, comprised of infrared absorption and Raman
scattering spectroscopy, is widely used for label-free optical sensing and
imaging in various scientific and industrial fields. The group theory states
that the two molecular spectroscopy methods are sensitive to vibrations
categorized in different point groups and provide complementary vibrational
spectra. Therefore, complete vibrational information cannot be acquired by a
single spectroscopic device, which has impeded the full potential of
vibrational spectroscopy. Here, we demonstrate simultaneous infrared absorption
and Raman scattering spectroscopy that allows us to measure the complete
broadband vibrational spectra in the molecular fingerprint region with a single
instrument based on an ultrashort pulsed laser. The system is based on
dual-modal Fourier-transform spectroscopy enabled by efficient use of nonlinear
optical effects. Our proof-of-concept experiment demonstrates rapid, broadband
and high spectral resolution measurements of complementary spectra of organic
liquids for precise and accurate molecular analysis.
