Optical parametric amplifications in parity-time symmetric negative-index materials

Parity-time (PT) symmetry has been studied quite extensively in optics. Recently, PT-symmetry has been explored even in the context of optical metamaterials. One major concern in optical metamaterial is the issue of loss. Though various schemes have been proposed and developed to address this issue, in this work we explore the possibility of exploiting the concept of parity-time symmetry to compensate for loss of signal strength in a negative index optical material. We have studied optical parametric amplification in parity-time symmetric negative refractive index metamaterials with second order nonlinearity. It is shown that the amplitude of the signal can be enhanced tremendously if the system is operated beyond the parity-time symmetric threshold. It is shown that even if one deviates from the exact condition of parity-time symmetry the amplification of the signal is pretty robust.