Terahertz coherent anti-Stokes Raman scattering microscopy

Vibrational spectroscopic imaging is useful and important in biological and medical studies. Yet, vibrational imaging in the terahertz region (<300 cm−1) under biologically relevant conditions is currently unavailable, as none of the available methods possesses a sufficient sensitivity and high spatial resolution at the same time. Here, we develop a terahertz coherent anti-Stokes Raman scattering (THz-CARS) microscope with a high sensitivity and high spatial resolution that shows chemically selective imaging of biological tissues by using low-frequency collective modes of the corresponding constituents, filling the existing energy scale gap for vibrational imaging in the THz region. The observation of collective modes of biomacromolecules, such as collagen and non-collagenous proteins, may have significant implications for elucidating their corresponding biological functions, and the methodology presented may find wider applications in biomedical research.