Two-channel interferometric detection for the compensation of phase fluctuation noise in nonlinear infrared microscopy

We demonstrate an interferometric implementation of nonlinear optical infrared microscopy in which a probe beam interrogates the refractive index change of samples that is induced by molecular vibrational absorption of an infrared pump beam. To compensate for the phase noise caused by the ambient airflow and external vibration, we configure two coupled Mach-Zehnder interferometers sharing a single microscope setup in the sample arm. Proper control over the phase between the two interference channels allows two simultaneous quadrature mode outputs. The validity of our method is proven by imaging polystyrene bead aggregates and comparing the images with the conventional single-channel results. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4773999]