Turbolence-induced orbital momentum in starlight: a source for a new type of light-matter interaction in circumstellar disks

Apart from helicity, photons might, under certain circumstances, also acquire an orbital angular momentum, which makes the wave front of the electromagnetic wave similar to a spiral phase ramp, with the Poynting vector creating a vortex around the direction of propagation where actually a zero intensity for the field is found (a point phase singularity) [1,2]. The formation of such photonic orbital momentum in electromagnetic waves has been recently demonstrated both in deflected (and phase-modified) light emitted near black holes [3] and in starlight propagating through turbolence [4]. Some stars (49 Ceti, HR 1895, HR 1529, HR 1577...) [4,5] are indeed associated with a turbolent assemblage of molecules or atoms and on encountering such turbolence, a propagating wave acquires an additional phase based on the spatial variation in the index of refraction of the medium.
Here I will first present the basic physical mechanisms for the formation of such "turbolent light": such orbital momentum can be imparted to light from interstellar media with a perturbed electron density function in the plane perpendicular to the propagation direction, revealing that the study of obrital momentum could give information about the spatial structures of the traversed inhomogeneous media. Then, I will talk about how it can influence the light-matter interaction around a star and about the idea to implement such electromagnetic waves in a code generally used to study molecular physics and condensed matter physics problems, and which allows to treat the nuclear motion and the spectroscopic response of ions, molecules and even solid objects in real time [6].

[1] L. Allen et al., Phys, Rev. A 45, 8185 (1992) [2] M. Harwit, Astrophys. J. 597, 1266–1270 (2003).
[3] F. Tamburini et al., Nature Physics 7, 195 (2011)
[4] D.W. Oesch and D. J. Sanchez, A&A 567, A114 (2014)
[5] D.W. Oeach et al., in Imaging and Applied Optics 2014, OSA Technical Digest (online) (Optical Society of America, 2014), paper PW1E.3 (proceedings of the Conference "Propagation Through and Characterization of Distributed Volume Turbulence", Seattle, Washington United States July 13-17, 2014) [6] X. Andrade, et al., J. Phys. Cond. Matt. 24, 233202 (2012)

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