A light beam can carry both spin angular momentum (SAM) and orbital angular
momentum (OAM). SAM is commonly evidenced by circular dichroism (CD)
experiments {\em i. e.} differential absorption of left and right-handed
circularly polarized light. Recent experiments, supported by theoretical work,
indicate that the corresponding effect with OAM instead of SAM is not observed
in chiral matter.
Isotropic materials can show CD when subjected to a magnetic field (MCD). In
Ref. ~\onlinecite{Mathevet2012} we report a set of experiments, under well
defined conditions, searching for magnetic orbital dichroism (MOD),
differential absorption of light as a function of the sign of its OAM. We
experimentally demonstrate that this effect, if any, is smaller than a few
10−4 of MCD for the Nd:YAG 4I9/2→4F5/2 transition.
This transition is essentially of electric dipole nature. We give an intuitive
argument suggesting that the lowest order of light matter interaction leading
to MOD is the electric quadrupole term.
We give here more experimental details and extra measurements.Comment: 6 pages, 7 figures. Supplemental material for a publication in Optics
Expres