Abstract
We analyze the imaging properties of the four-wave mixing (FWM) technique, which allows high-resolution three dimensional (3D) refractive index (RI) mapping inside transparent materials using FWM microscopy. The analysis is based on a modified 3D beam propagation method. By comparing the numerical calculation results with experimental ones, we clarify that the measured RI profiles include artifacts that originate from (a) the refraction of the excitation beam by sample structures and (b) the power variation of FWM signals due to the finite numerical aperture of the collector lens. Artifact (a) can be compensated for using a heuristic method, and the amount of artifact (b) can be reduced by increasing the numerical aperture of the collector lens. These results provide important guidelines for reducing the amount of artifacts in the practical implementation of the FWM technique.