Simultaneous measurement of depth-resolved refractive index field and deformation field inside polymers during the curing process

A method based on phase-sensitive optical coherence tomography (PhS-OCT) has recently been used to visualize curing process inside polymers [Appl. Phys. Lett. 116: 054103 (2020)]. Based on this proven method, we further proposed a refractive index model to determine curing induced displacements. For validation, the curing process of a light-cured resin droplet was first monitored by recording a time series of spectral images. Amplitude images and phase difference maps were then calculated from the spectral images. Finally, according to the proposed refractive index model, amplitude and phase information were used together to simultaneously measure refractive index fields and displacement fields. The results show that the time-dependent refractive index field is generalized by a piecewise function consistent with the polymerization kinetics; only the displacements with the piecewise functional feature, similar to the refractive index change, can characterize polymerization shrinkage.