Nanointerferometric amplitude and phase reconstruction of tightly focused vector beams

Abstract

Highly confined vectorial electromagnetic field distributions are an excellent tool for detailed studies in nano-optics, such as nonlinear microscopy1, advanced fluorescence imaging2,3 or nanoplasmonics4,5. Such field distributions can be generated, for instance, by tight focusing of polarized light beams6,7,8,9. To guarantee high resolution in the investigation of objects with subwavelength dimensions, precise knowledge of the spatial distribution of the exciting vectorial field is of utmost importance. The full-field reconstruction methods presented to date involve, for example, complex near-field techniques10,11,12,13. Here, we demonstrate a simple and straightforward-to-implement measurement scheme and reconstruction algorithm based on the scattering signal of a single spherical nanoparticle as a field probe. We are able to reconstruct the amplitudes and relative phases of the individual focal field components with subwavelength resolution from a single scan measurement without the need for polarization analysis of the scattered light. This scheme has the potential to improve microscopy and nanoscopy techniques. An easily implementable reconstruction scheme is demonstrated for determining the full vectorial amplitude and relative phase distributions of highly confined electromagnetic fields with subwavelength resolution from a single-scan measurement. This scheme will help improve microscopy and nanoscopy techniques.