A system is disclosed for detecting a non-linear coherent field induced in a sample volume. The system includes a first source for generating a first electromagnetic field at a first frequency, a second source for generating a second electromagnetic field at a second frequency, first optics for directing the first and second electromagnetic fields toward the sample volume, second optics for directing the first and second electromagnetic fields toward a local oscillator volume, and an interferometer. The interferometer is for interfering a first scattering field that is generated by the interaction of the first and second electromagnetic fields in the sample volume, with a second scattering field that is generated by the interaction of the first and second electromagnetic fields in the local oscillator volume.