New optical microscope captures atomic world with one-nanometer precision

Researchers have developed a groundbreaking optical microscopy technique called ULA-SNOM (ultralow tip oscillation amplitude scattering-type scanning near-field optical microscopy) that achieves one-nanometer resolution, enabling the visualization of individual atoms using light rather than electrons. This innovation overcomes the longstanding diffraction limit of traditional optical microscopes, which restricts resolution to about 200 nanometers—too coarse to observe atomic-scale features. By precisely controlling a polished silver scanning tip to oscillate with an amplitude of just 0.5 to 1 nanometer under ultrahigh vacuum and cryogenic conditions (8 Kelvin), the team created a plasmonic cavity that confines light to a cubic nanometer volume, allowing detailed optical interaction with single atoms. The ULA-SNOM technique builds on existing scattering-type scanning near-field optical microscopy (s-SNOM) but significantly improves resolution by minimizing tip oscillation amplitude, balancing signal strength and noise reduction. The setup uses a 633-nanometer red laser to