Focusing characteristics of a 4 πparabolic mirror light-matter interface

Journal of the European Optical Society-Rapid Publications, May 2017

Background Focusing with a 4 π parabolic mirror allows for concentrating light from nearly the complete solid angle, whereas focusing with a single microscope objective limits the angle cone used for focusing to half solid angle at maximum. Increasing the solid angle by using deep parabolic mirrors comes at the cost of adding more complexity to the mirror’s fabrication process and might introduce errors that reduce the focusing quality. Methods To determine these errors, we experimentally examine the focusing properties of a 4 π parabolic mirror that was produced by single-point diamond turning. The properties are characterized with a single 174Yb + ion as a mobile point scatterer. The ion is trapped in a vacuum environment with a movable high optical access Paul trap. Results We demonstrate an effective focal spot size of 209 nm in lateral and 551 nm in axial direction. Such tight focusing allows us to build an efficient light-matter interface. Conclusion Our findings agree with numerical simulations incorporating a finite ion temperature and interferometrically measured wavefront aberrations induced by the parabolic mirror. We point at further technological improvements and discuss the general scope of applications of a 4 π parabolic mirror.

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Focusing characteristics of a 4 πparabolic mirror light-matter interface

Alber et al. Journal of the European Optical Society-Rapid Publications Focusing characteristics of a 4π parabolic mirror light-matter interface Lucas Alber 0 1 3 4 Martin Fischer 0 1 3 4 Marianne Bader 0 1 3 4 Klaus Mantel 1 4 Markus Sondermann 0 1 3 4 Gerd Leuchs 0 1 2 3 4 0 Department of Physics, Friedrich-Alexander University Erlangen-Nürnberg (FAU) , Staudtstraße 7/B2, 91058 Erlangen , Germany 1 Max-Planck-Institute for the Science of Light , Staudtstr. 2, 91058 Erlangen , Germany 2 Department of Physics, University of Ottawa , 75 Laurier Avenue East, ON K1N 6N5 Ottawa , Canada 3 Department of Physics, Friedrich-Alexander University 4 Erlangen-Nürnberg (FAU) , Staudtstraße 7/B2, 91058 Erlangen , Germany Background: Focusing with a 4π parabolic mirror allows for concentrating light from nearly the complete solid angle, whereas focusing with a single microscope objective limits the angle cone used for focusing to half solid angle at maximum. Increasing the solid angle by using deep parabolic mirrors comes at the cost of adding more complexity to the mirror's fabrication process and might introduce errors that reduce the focusing quality. Methods: To determine these errors, we experimentally examine the focusing properties of a 4π parabolic mirror that was produced by single-point diamond turning. The properties are characterized with a single 174Yb+ ion as a mobile point scatterer. The ion is trapped in a vacuum environment with a movable high optical access Paul trap. Results: We demonstrate an effective focal spot size of 209 nm in lateral and 551 nm in axial direction. Such tight focusing allows us to build an efficient light-matter interface. Conclusion: Our findings agree with numerical simulations incorporating a finite ion temperature and interferometrically measured wavefront aberrations induced by the parabolic mirror. We point at further technological improvements and discuss the general scope of applications of a 4π parabolic mirror. Atom-photon coupling; Free space; Quantum optics; Ion trapping; 4Pi parabolic mirror; 4Pi microscopy; Confocal microscopy - Background Free space interaction between light and matter is incorporated as a key technology in many fields in modern science. The efficiency of interaction influences measurements and applications ranging from various kinds of fundamental research to industrial applications. New innovations and new types of high precision measurements can be triggered by improving the tools needed for a light-matter interface. To achieve high interaction probability with a focused light field in free space, an experimental scheme using parabolic mirrors for focusing onto single atoms has been developed in recent years [1–3]. This scheme relies on mode matching of the focused radiation to an electric dipole mode (cf. Ref. [4] and citations therein). Focusing in free-space experiments is usually done with state-of-the-art lens based imaging systems [5–8]. Single lenses, however, suffer from inherent drawbacks like dispersion induced chromatic aberrations, optical aberrations, and auto-fluorescence, respectively. Most of these limitations can be corrected to a high degree by precisely assembling several coated lenses in a lens-system, e.g. in a high numerical aperture (NA) objective. Although solving some problems, multi-lens-systems induce new problems such as short working distances, low transmission for parts of the optical spectrum, the need for immersion fluids, and high costs, respectively. Therefore, multi-lens systems are often application specific providing best performance only for the demands that are most important for the application. Mirror based objectives are an alternative to lens-based systems and can overcome some of these problems. The improvement is based on a mirror’s inherent property of being free from chromatic aberrations. The nearly wavelength independent behavior also leads to a homogeneous reflectivity for a large spectral window. Comparing the © The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. reflectivity of mirrors to the transmission of lens based objectives, mirrors can sometimes also surpass lens-based systems. But surprisingly, they are rarely used when high interaction efficiency is required. This lack in application may be due to the fact that reflecting imaging systems, like the Cassegrain reflector, cannot provide a high NA. A high NA is however needed for matching the emission pattern of a dipole, which spans over the entire solid angle. The limitation in NA consequently constitutes a limitation in the maximum achievable light-matter cou (...truncated)


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Lucas Alber, Martin Fischer, Marianne Bader, Klaus Mantel, Markus Sondermann, Gerd Leuchs. Focusing characteristics of a 4 πparabolic mirror light-matter interface, Journal of the European Optical Society-Rapid Publications, 2017, pp. 14, Volume 13, Issue 1, DOI: 10.1186/s41476-017-0043-y