Tapered fiber-based shear force scanning photoacoustic microscopy

Abstract

Optical resolution photoacoustic microscopy (OR-PAM) provides high optical contrast and lateral resolution. However, the resolution of a typical OR-PAM using an objective lens is limited to not exceeding Abbe's optical diffraction limit. In this study, a lensless shear force scanning PAM is presented. Instead of a lens, the system uses an imaging probe that combines a non-coated tapered fiber with a quartz tuning fork (QTF). A shear force feedback mechanism is used to maintain a tens of nm (near-field) distance between the fiber tip and the sample. With the system, PA signals generated in the near field of a gold sputtered glass sample were successfully acquired. We also performed 2D PA scanning experiments and obtained PA images of gold cube samples with high lateral resolution. This study demonstrates the existence of a near field PA signal and shows its potential for super-resolution scanning PAM.