Observation of Poynting’s vector reversal in an active photonic cavity

Optical power flow along an active cavity having net gain can differ dramatically from that in a passive cavity. We report the first observation of Poynting’s vector reversal in an active cavity under scattering boundary conditions. At a sub-lasing gain, which we call Poynting’s threshold, a null develops in Poynting’s vector, which divides the cavity into sections with oppositely directed energy flows. Furthermore, we demonstrate that the direction of Poynting’s vector at a fixed point in an active cavity can be controllably reversed without changing its magnitude via an intra-cavity passive element, thereby suggesting a potential methodology for optical switching. © 2016 Optical