Light-driven PT symmetry in colloids with gain and loss nanoparticles

Abstract

We consider a planar layer of a colloid solution with gain and loss nanoparticles. The concentration of the particles of both types is assumed to provide balanced light amplification and dissipation in the corresponding effective medium. The normally incident plane electromagnetic wave causes the spatial separation of gain and loss particles due to the pulling and pushing ponderomotive forces that act on active and absorptive particles, respectively. We show that at the moderate intensity of incident light, the emerging stationary distribution of the gain and loss nanoparticles forms a parity–time (PT)-symmetric profile of the effective dielectric permittivity satisfying the condition εeff(−z)=εeff∗(z). The magnitude of the imaginary part of the colloid refractive index can be controlled by the intensity of incident light, which makes the proposed tunable PT-symmetric layer a promising tool for studying non-Hermitian optical phenomena.