Molecular spectroscopic imaging using a white-light laser source

Coherent anti-Stokes Raman scattering (CARS) microscopy has become a powerful technique for label-free and noninvasive imaging of chemical and biological systems at the molecular level. However, most CARS studies have focused on a limited molecular species such as lipids, and have provided monochromatic images typically at the CH stretch bands. In the present study, we have extended the CARS technique from monochromatic imaging (microscopy) to multi-color imaging (microspectroscopy). We employed a multiplex CARS process in order to obtain spectral information of the CARS signal. For the broadband Stokes laser, a white-light laser source is used. The white-light laser is generated by injecting ultrashort laser pulses into a novel photonic crystal fiber (PCF). Owing to an ultrabroadband spectral profile of the white-light laser, a wide range of the vibrational resonances can be investigated. We performed label-free and multicolor molecular spectroscopic imaging of biological samples through the multiplex CARS process.