Spatial eigenmodes of atmospheric turbulence

Abstract: Free space quantum communication can benefit from encoding information into highdimensional
quantum states of light. One possibility of such encoding is to use orbital
angular momentum (OAM) of photons. However, the wavefronts of the spatial modes
of light endowed with OAM, such as Laguerre-Gauss (LG) modes, are fragile with
respect to fluctuations of the refractive index of air. In the present thesis, we explore
the potential of alternative encoding high-dimensional states of photons – into spatial
eigenmodes of atmospheric turbulence.
Specifically, we study the properties of eigenvalues and eigenvectors of the “turbulence
operator”, which describes the action of a single realisation of the atmospheric
turbulence on light beams propagated over a distance of 400m in the air and confined
to a circular aperture in the receiver plane. This operator takes into account beam
diffraction, refraction on the inhomogeneities of the dielectric susceptibility of air, and
losses arising from the finite sized aperture and from the finite dimensional basis used
to represent the turbulence operator.
We consider two sets of basis modes on a circle: the Zernike polynomials and the
LG modes. We show that the former set of functions is rather useless, since it is not
possible to accurately represent light beams propagated in vacuum or in turbulence.
For the LG basis set, we use a basis dimension limited to 240 mode functions and
investigate how the proximity of the eigenvalues to unity depends on the specific choice
of the mode functions. We find that the eigenmodes whose eigenvalues are close to
unity are highly localized in the transverse plane

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• Location: Deutsche Nationalbibliothek Frankfurt am Main
• Extent: Online-Ressource
• Language: Englisch
• Notes: Universität Freiburg, Bachelorarbeit, 2018

Classification and Topics

• Keyword: Atmosphärische Turbulenz

Contributors, Places and Time

• Event: Veröffentlichung
• (where): Freiburg
• (who): Universität
• (when): 2019
• Creator: Schuler, Jan
• Contributor: Buchleitner, Andreas ; Shatokhin, Vyacheslav N.

Further information

• DOI: 10.6094/UNIFR/150010
• URN: urn:nbn:de:bsz:25-freidok-1500108
• Rights: Der Zugriff auf das Objekt ist unbeschränkt möglich.