Phase-controlled nonlinear interferometry for the selective detection of coherent anti-Stokes Raman scattering signals

We have controlled the relative phases of two successively generated coherent anti-Stokes Raman scattering (CARS) signals with dispersive material placed between the two CARS signals. A home-made phase shifting unit made of BK7 glass was used as the dispersive medium. To control the relative phase between two CARS signals that changes with the wavelength of Stokes beam scanned, we adjusted the thickness of phase shifting unit adjustable to compensate for the change in a wide spectral range. With this nonlinear interferometric technique, we could selectively suppress the undesired contribution from the 3rd order nonlinear susceptibility.