Wavevector resonance modulation in multilayered nanostructures for sub-λ/10 label-free super-resolution imaging

Label-free super-resolution imaging based on the spatial-frequency-shift (SFS) effect enables conventional microscopes to surpass the diffraction limit, holding significant promise for nanoscale inspection in materials science and biology. However, current SFS approaches generally face a practical trade-off in obtaining both the ultra-high resolution and the high signal-to-noise ratio (SNR) when using high lateral wavevector (kx) illumination supported by a natural waveguide or single metal film. Here, we proposed a wavevector resonance modulation scheme in multilayered nanostructures that introduces an enhanced deep SFS effect, which is realized by surface plasmon polariton illumination supported by a designed multilayer with relaxed fabrication tolerance. This approach simultaneously achieves a peak-to-peak distance of ∼70 nm under the excitation wavelength of 780 nm, a resonance-enhanced illumination field, and a more than 10-fold expansion for the coherent transfer function (CTF). We demonstrated the simple excitation process by means of gratings and presented an application in nano-imaging experiments for label-free particles. Results show the advance in the resonance-enhanced illumination modulation method for super-resolution imaging, enabling conventional microscopes to detect and distinguish label-free nanoscale structures with characteristic lateral scales down to sub-λ/10.