Center for Relativistic Laser Science

2019 RamanFest 

Abstract:

In CARS imaging, with a non-resonant background, the dark dip exhibits at the interface between the objects and the medium. Although a variety of CARS imaging techniques have been already developed to eliminate a non-resonant contribution to the CARS signal, it still remains a promising task to remove such interfacial dip at the same time. Here, we report a new approach of two-color resonant CARS microscopy using two Stokes beams and one pump beam to concurrently eliminate both undesirable non-resonant background and interfacial dip. Two resonant CARS signals are simultaneously acquired at each vibrational mode of the target molecules in objects, such as polystyrene beads, lily pollens, mamalian cells, and nematode C. elegans, and the water molecules in the surrounding medium. By subtracting these two complementary images with a non-resonant background correction factor, coherent CARS signal to the molecular vibration of interests could be purely obtained without a loss of signal intensity. Because we employed a super-continuum laser source (500 cm^-1 ~ 2,900 cm^-1) that can continuously detect the signals in a broad range of molecular vibrations, our CARS microscopy will be extensively used for investigating the molecular structures at the interfaces as a powerful tool for multi-color label-free imaging.