Twisted Laser Beams and Light Springs
IPFN, Instituto Superior Técnico, Universidade de Lisboa
We discuss the physics of twisted laser beams, and present some recent results and new concepts. These beams carry a finite amount of orbital angular momentum (OAM), which can change the main characteristics of laser-matter interactions. Of particular relevance are the new selection rules for atomic radiative transitions. Different kinds of new processes occurring in solid targets and in plasmas have been identified. Not only twisted photons but also twisted scalar waves (such as plasmons and phonons) can be excited. In particular, these scalar waves with OAM display qualitatively new kinetic properties, such as modified Landau resonances.
We also discuss the related concept of light strings, and the formation of wakefields and fractional vortices. Their impact on particle acceleration, nonlinear wave mixing, magnetic field generation and laser amplification is considered. Other nonlinear effects associated with twisted laser beams propagating in a medium are discussed. This includes Raman and Brillouin stimulated scattering, modified forms of the inverse Faraday effect, radiation pressure and high harmonic generation. The results can be relevant to atomic physics, nonlinear optics, astrophysics and plasmas.