Fluorescence modulation of quantum dots in subsurface defects of optical elements by a linearly polarized light

The limited excitation efficiency of quantum dots in the detection of subsurface defects in optical elements by quantum dot fluorescence gives rise to insufficient accuracy. To enhance the excitation efficiency of quantum dots, we studied the modulation of the polarization direction of linearly polarized incident light on quantum dot fluorescence. We first apply density matrix evolution theory to study the quantum dots interacting with linearly polarized incident light and emitting fluorescence. The fluorescence intensity exhibits cosine oscillations versus modulated laser polarization. It reaches a maximum value at the polarization angle zero, and then decreases as the angle becomes larger until π/2. The experimental results for the quantum dot in both solutions and subsurface defect of optical elements confirmed these results. For optical elements tagged with CdSe/ZnS quantum dots, the fluorescence intensity increases by 61.7%, and the area for the detected subsurface defects increases by 142.9%. Similarly, for C and InP/ZnS quantum dots, there are also increases in both the fluorescence intensity and the area of subsurface defects. Our study suggests that the subsurface defect detection in optical elements by the linearly polarized incident light could enhance the detection accuracy of subsurface defects in optical elements, and potentially achieve super-resolution imaging of subsurface defects.