Azimuthally polarized vortex vector optical field enhances the lateral resolution of two-photon fluorescence microscopy imaging

Vector optical fields (VOFs) have attracted significant interest owing to their unique properties, which are distinct from those of traditional scalar optical fields. One of the most important properties is the ability to form a smaller focal volume. We have introduced the Azimuthally Polarized Vortex Vector Optical Field (APV-VOF) with this property into two-photon excitation fluorescence imaging (TPEF) to improve the lateral resolution of the imaging. We conducted detailed research from both numerical and experimental perspectives. Our numerical simulations predict that using APV-VOF as the excitation source, instead of the conventional linearly polarized Gaussian beam, can enhance the lateral resolution by 18.4% in a TPEF system. We verified through experiments using fluorescent beads and colorectal cancer tissue sections that APV-VOF can improve the resolution of two-photon excitation fluorescence imaging.