CARS micrscopy and micro-spectroscopy
CARS (coherent anti-Stokes Raman scattering) is a third order nonlinear optical process that generates its signals from the vibrational response of the sample. Due to its high signal level and chemical selectivity, CARS microscopy is emerging as a powerful chemical imaging tool for material and biology studies. With a broadband laser pulse, CARS can also be configured to detect vibrational spectrum of a sample in a single measurement (multiplex CARS). However, CARS signals always accompany a background from the electronic response of the sample and its interference with the vibrational signals has been the major problem in applications. We combine the concepts of laser pulse shaping and spectral interferometry to develop a new version of multiplex CARS technique that not only extracts spontaneous Raman-like spectrum but also amplifies the desired vibrational signal significantly. We are currently working on further sensitivity improvement and its applications to material and biological systems.