Nonlinear photon-atom coupling with 4Pi microscopy

Yue-Sum Chin,Christian Kurtsiefer,Matthias Steiner

doi:10.1038/s41467-017-01495-3

Yue-Sum Chin, Christian Kurtsiefer + Show 1 more

Open Access

https://doi.org/10.1038/s41467-017-01495-3

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Abstract

Implementing nonlinear interactions between single photons and single atoms is at the forefront of optical physics. Motivated by the prospects of deterministic all-optical quantum logic, many efforts are currently underway to find suitable experimental techniques. Focusing the incident photons onto the atom with a lens yielded promising results, but is limited by diffraction to moderate interaction strengths. However, techniques to exceed the diffraction limit are known from high-resolution imaging. Here we adapt a super-resolution imaging technique, 4Pi microscopy, to efficiently couple light to a single atom. We observe 36.6(3)% extinction of the incident field, and a modified photon statistics of the transmitted field–indicating nonlinear interaction at the single-photon level. Our results pave the way to few-photon nonlinear optics with individual atoms in free space.

Highlights

Implementing nonlinear interactions between single photons and single atoms is at the forefront of optical physics
To realize nonlinear interactions between a few propagating photons and a single atom in free space, the photons need to be tightly focused to a small volume[1,2,3,4,5,6,7,8]
It is well-known that a small focal volume requires optical elements, which cover a large fraction of the solid angle[9]

Summary

Introduction

Implementing nonlinear interactions between single photons and single atoms is at the forefront of optical physics. To realize nonlinear interactions between a few propagating photons and a single atom in free space, the photons need to be tightly focused to a small volume[1,2,3,4,5,6,7,8] From highresolution imaging, it is well-known that a small focal volume requires optical elements, which cover a large fraction of the solid angle[9]. While standard confocal optical microscopy accomplished already very small probe volumes, the excitation light is focused through a lens that can cover only up to half of the solid angle, limiting the axial resolution due to a focal volume elongated along the optical axis This limitation has been overcome by using two opposing lenses with coinciding focal points, known as 4Pi arrangement[10] The path of the incident beam is split, and the object is coherently illuminated by two counter-propagating parts of the field simultaneously (Fig. 1a). The 4Pi arrangement leads to a sizeable nonlinearity of the interaction at the single-photon level which is manifested in the intensity correlations of the transmitted field

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