Phase-sensitive optical coherence tomography for non-contact monitoring photocuring process

A method combining phase-contrast technique and spectral-domain optical coherence tomography (OCT) has been recently proposed for visualizing curing behaviors inside polymers (2020 Appl. Phys. Lett. 116 054103). Here, based on the method, a non-contact and highly-sensitive optical sensor is further developed to monitor the photocuring process of light-cured polymers. Compared with the existing method, the proposed optical sensor features two distinct advantages: (a) the sensor uses a point-detection OCT, rather than a line-field OCT, to capture the interference signal, which significantly improves its practicability and the measuring speed; (b) the sensor can simultaneously monitor the shrinkage strains and refractive index variations during a photocuring process, featuring enhanced functionality in practical applications. For validation, a cure monitoring experiment was carried out, proving that the sensor can accurately monitor the shrinkage strain and refractive index variation during the polymer photocuring process. The polymer coating fabrication process and the polymer adhesive process were also monitored, showing the effectiveness and practicability of the sensor.