Focusing characteristics of a 4 πparabolic mirror light-matter interface

Abstract

Abstract 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.

Keywords

• Atom-photon coupling
• Free space
• Quantum optics
• Ion trapping
• 4Pi parabolic mirror
• 4Pi microscopy