Single-molecule-resolution ultrafast near-field optical microscopy via plasmon lifetime extension

Abstract

Metal nanostructures support plasmon oscillations on their surfaces, which normally decay very quickly. Nevertheless, the lifetime of these oscillations can be extended near a longer lifetime particle, e.g., a molecule. We utilize this phenomenon for ultrahigh (single-molecule) resolution ultrafast apertureless (scattering) applications. We demonstrate the phenomenon with the numerical solutions of 3D Maxwell equations. We use a nm-sized quantum emitter (QE) for the long lifetime particle. We place the QE at the apex of a metal-coated atomic force microscope tip. We illuminate the tip with a femtosecond laser. The near-field on the metal apex decays quickly. After some time, one receives the scattering signal only from the vicinity of the QE. Thus, the resolution becomes single-QE size. We propose the use of a stress-induced defect center in a 2D material as the QE. The tip indentation of the 2D material, transferred to the tip, originates a defect center located right at the sharpest point of the tip, which is exactly at its apex. Our method can equally be facilitated for single-molecule-size chemical manipulation.