The performances of an optical trap depend on the ability to reduce its transverse size, such that one can optimally control the relative position of the atom and eventually get an inter-traps distance as small and precise as possible. The size of a conventional diffraction-limited trap can be defined by the Abbe radius of its optical hotspot.
However, it is possible to reduce the size of the hotspot beyond Abbe’s limit using the phenomenon of superoscillations that allows band-limited function to locally oscillate faster than its highest Fourier component. Optical superoscillations are rapid subwavelength spatial variations of the intensity and phase of light, occurring in complex electromagnetic fields formed by the interference of several coherent waves. In recent years, the understanding of the superoscillatory phenomenon in optics has led to the development of superoscillatory lensing, imaging, metrology technologies and trapping of nanometres-size dielectric objects.
In our paper, published in Communications Physics, we report the trapping of a single atom in a superoscillatory optical trap where the transverse size is subwavelength and below the Abbe’s limit by a factor 0.69(3).
Superoscillatory traps can find applications when compact and tunable ensembles of trapped atoms are needed for quantum simulation of many-body effects, cooperative quantum metasurfaces, and for single-molecule quantum chemistry.