1D line-scan imaging of gold nanoparticles beyond diffraction limit with white light via absorbance modulation nanoscopy

Far-field reflection microscopes are widely used due to minimal sample preparation and environmental requirements, though their lateral resolution is limited by diffraction. Absorbance Modulation Imaging (AMI) enables a lateral resolution enhancement below the diffraction limit by using a photochromic absorbance modulation layer (AML). A confinement beam with a TEM01* intensity pattern converts exposed AML regions from transparent to opaque, forming a subwavelength aperture by non-linear interaction. This aperture narrows the point spread function (PSF) of a Gaussian measurement beam.¹ In this study, a 1.17-fold lateral resolution enhancement was achieved for the first time using a broadband white light source (450–700 nm) in reflection microscopy. Experimental results show that the PSF of gold nanoparticles, which is measured using an amplified photodiode, is reduced by approximately 14.4% compared to the diffraction-limited PSF at a numerical aperture (NA) of 0.65. This confirms the feasibility of hyperspectral AMI in reflection mode. Additionally, we used a TEM01* (doughnut-shaped) confinement beam, enabling isotropic PSF confinement. We also demonstrate that the measurement light intensity is sufficient for effective surface visualization.