Abstract
Abstract We study how nanophotonic structures can be used for determining the position of a nearby nanoscale object with subwavelength accuracy. Through perturbing the near-field environment of a metasurface transducer consisting of nano-apertures in a metallic film, the location of the nanoscale object is transduced into the transducer’s far-field optical response. By monitoring the scattering pattern of the nanophotonic near-field transducer and comparing it to measured reference data, we demonstrate the two-dimensional localization of the object accurate to 24 nm across an area of 2 × 2 μm. We find that adding complexity to the nanophotonic transducer allows localization over a larger area while maintaining resolution, as it enables encoding more information on the position of the object in the transducer’s far-field response.
Highlights
Nanoscale metrology is imperative for advances in nanoscience, biology and semiconductor technology
We have constructed a nanophotonic nearfield transducer for detecting the position of a subwavelength object, which is encoded in the far-field radiation pattern of the transducer
By monitoring the radiation pattern and using a library-based technique, we demonstrated the retrieval of the object position accurate to 24 nm across an area of 2 × 2 μm
Summary
Nanoscale metrology is imperative for advances in nanoscience, biology and semiconductor technology. The intensity of the scattered signal as a function of position, usually measured on a bucket detector with a single degree of freedom, gives information on the permittivity distribution of the sample [7] or on the optical near field supported by the sample. We aim to construct an optical near-field transducer in the form of a nanophotonic target structure that determines the position of a nanoscale perturbation located near the structure on basis of collected scattered light. The ‘sample’ in s-NSOM terms becomes in our work a transducer that encodes the location of a scatterer – the known tip in s-NSOM, but here the unknown variable under study – into a far-field optical response. Our approach to retrieving the scatterer position purely from optical fields is to not use a bucket detector for total scatterered intensity, but instead to exploit the
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