The generation of broadband terahertz radiation by optical rectification in a gradient planar waveguide is investigated. The conditions for the capture of optical and terahertz pulses and collinear propagation of their bound states are studied. The waveguide structure significantly reduces the diffraction spreading of generated terahertz pulses in comparison to a homogeneous bulk medium.
The propagation of light pulses through the chirped Bragg structures with superimposed PT-symmetric complex potential (gain and loss) has been studied using the numerical methods. The reflective properties of such structures in the regime below PT-symmetry breaking threshold are discussed. It is shown, that due to the balanced amplification of different spectral components of a reflected pulse such structures can effectively transform the profile of a reflected pulse and at the same time amplify its amplitude.