We develop a free-carrier theory of the optical absorption of light carrying
orbital angular momentum (twisted light) by bulk semiconductors. We obtain the
optical transition matrix elements for Bessel-mode twisted light and use them
to calculate the wave function of photo-excited electrons to first-order in the
vector potential of the laser. The associated net electric currents of first
and second-order on the field are obtained. It is shown that the magnetic field
produced at the center of the beam for the ℓ=1 mode is of the order of a
millitesla, and could therefore be detected experimentally using, for example,
the technique of time-resolved Faraday rotation.Comment: Submitted to Phys. Rev. Lett. (23 Jan 2008