An ideal nanocomposite for gas-phase sensing with coherent anti-Stokes Raman scattering

A nano-optical solution to the problem of coherent background suppression in coherent anti-Stokes Raman scattering (CARS) is proposed. Based on the arguments of effective-medium theory for weakly nonlinear nanocomposites, we discuss a design of nanocomposite systems optimized for CARS gas-phase sensing. A nanocomposite with a properly engineered morphology can predominantly concentrate the pump field in the areas of low refractive index, e.g., in a network of pores, substantially reducing the coherent background in CARS spectra and enhancing the resonant CARS signal.