Scattering of linear and nonlinear waves in a waveguide array with a PT-symmetric defect

We study the scattering of linear and nonlinear waves in a long waveguide array with a parity-time (PT)symmetric defect created by two waveguides with balanced gain and loss. We present exact solutions for the scattering of linear waves on such a defect, and then demonstrate numerically that the linear theory can describe, with a good accuracy, the soliton scattering in the case of weak nonlinearity. We reveal that the reflected and transmitted linear and nonlinear waves can be amplified substantially after interaction with the PT-symmetric defect thus allowing an active control of the wave scattering in the array.