Quadriwave lateral shearing interferometry as a quantification tool for microscopy. Application to dry mass determination of living cells, temperature mapping and vibrational phase imaging.

A Quadri-Wave Lateral Shearing Interferometer (QWLSI) is an efficient tool for measuring phase gradients of optical beams along two perpendicular directions. Post-processing integration then allows obtaining the complete phase spatial distribution of the beam. By placing a QWLSI on the exit image plane of such a microscope, we are able to measure the complex field spatial distribution in this plane, and then to retrieve the quantitative optical path difference (OPD) of the observed sample. Here, we demonstrate that we can extend the technique to new applications, were different physical phenomena produce a given sample-induced change in the phase of the exit optical beam that modulates the incident wavefront. More precisely, we used direct refractive-induced OPD, thermal-induced OPD, and resonant vibrational-induced OPD to produce phase contrast images of living cells, temperature distribution of complex patterns of nanostructures, and Raman spectra of polystyrene beads, respectively. In the case of refractive-induced OPD of living cells, we also show that the OPD distribution of a living cell can be used to monitor its dry mass during the cell cycle.