Imaging of nanoscale birefringence using polarization-resolved chromatic confocal microscopy

We demonstrate a homebuilt confocal microscope with similar to 60 nm axial resolution to visualize the optical path length (OPL) of liquid crystals (LCs) inside a 2-domain alignment LC cell. Since the microscope is sensitive to light polarization, it is capable of determining LC orientation by accounting for the OPL variation, Delta OPL. The resolution of birefringence depends on the measured Delta OPL from two cross-polarized channel detections, of which the concept is different from other polarization-resolved optical imaging techniques, but is relatively simple in optical layout and analysis. The different orientations of LCs and the voltage-dependent LC rotation properties in the 2-domain LC cell are monitored and analyzed. Additionally, the complicated LC orientation distribution at the junction of the two domains with different alignments can be clearly observed. It shows great possibilities of examining tissue birefringence related to disease progression and tiny birefringence variation of electro-optical materials under an external field, which are hardly resolved by conventional optical imaging techniques. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

The article introduces a homemade confocal microscope with high resolution for visualizing optical path length and orientation of liquid crystals. By measuring the optical path length variation Delta OPL, LC orientation and birefringence resolution can be determined. The technique is simple and efficient, capable of monitoring different LC orientations and rotation properties under an electric field.