Off-resonant Fano-enhanced single-molecule-resolution imaging with a CW source
Ramazan Şahin, PhD · · 1 min read · Updated
Simulations show how a defect at the tip apex can push near-field optical imaging towards 1 nm resolution under continuous-wave light.
In apertureless scanning near-field optical microscopy (a-SNOM), the size of the tip apex usually caps the resolution at around 10 nanometres. This numerical study argues that about 1 nanometre is within reach using an ordinary continuous-wave (CW) laser, by making use of Fano interference.
The key element is a defect centre that appears spontaneously on the very end of an AFM tip with a metal coating and behaves as a quantum object. The interference it creates lets a stronger plasmon mode at 597 nanometres, which would normally sit off resonance, act as if it were resonant with the 520-nanometre driving light. Since the effect appears only right below the defect, a roughly 1-nanometre-wide, defect-specific contribution forms inside the larger hotspot at the apex; the paper stresses that the metallic hotspot as a whole does not shrink to 1 nanometre. With this field, full three-dimensional Maxwell simulations tell apart two model objects placed very close to one another.
This summary is based on the paper's published abstract; the author list, journal and DOI are shown in the citation box.