US Patent 9664614 Method for high resolution sum-frequency generation and infrared microscopy

A method for analyzing a sample with a light probe with a spatial resolution smaller than the wavelength of the light probe comprising the steps of: —illuminating the sample by a first light pulse saturating a vibrational and/or electronic transition, said light pulse presenting an intensity spatial distribution on the sample presenting at least one minimum wherein saturation does not occur, —measuring the local absorbance properties and/or the local second order non-linear susceptibility of the sample by using a second light pulse forming the light probe at a wavelength corresponding to said electronic and/or vibrational transition, wherein the second light pulse overlap said first light pulse intensity minimum.