Laser profile changes due to photon–axion induced beam splitting

This paper looks at a potentially unique measurable due to photon–axion coupling in an external magnetic field. Traditionally, detection of such a coupling has focused on observation of an optical rotation of the beamʹs polarization due to either a birefringence or a path length difference (p.l.d.) between two polarization states. Such experiments, utilizing mirror cavities, have been significantly limited in sensitivity; approaching coupling strengths of ~ga=10−7 GeV−1. Here the bifurcation of a beam in a cavity is explored along with the possibility of measuring its influence on the photon density. Simulations indicate that coupling to levels ga~10–12 are, with an appropriate choice of cavity, within measurable limits. This is due to a rapid growth of a signal defined by the energy loss from the center accompanying an increase in the region beyond the beam waist. Finally, the influence of a non-zero axion mass is explored.