Raman-induced Kerr effect microscopy with balanced detection

We present a new coherent Raman scattering technique, which we call balanced-detection Raman-induced Kerr effect. The technique relies on a balanced detection architecture, inspired to that applied for electro-optic sampling in the terahertz domain, which allows one to sensitively measure the Raman-induced Kerr effect-induced polarization rotation of the Stokes field. Balanced detection allows for an intrinsic rejection of laser noise, thus making possible to approach shot-noise limited conditions even when using fiber laser sources and relatively low modulation frequencies. Balanced-detection Raman-induced Kerr effect removes both linear and nonlinear background, provides self-heterodyne amplification of the nonlinear Raman signal, and scales linearly the sample concentration. Furthermore, by properly changing the detection conditions, it allows the reconstruction of the full complex vibrational response, both in amplitude and phase, greatly increasing chemical selectivity in single-color excitation.