  The spectral behaviour and the real-time operation of Parity-Time (PT PT)
symmetric coupled resonators are investigated. A Boundary Integral Equation
(BIE) model is developed to study these structures in the frequency domain. The
impact of realistic gain/loss material properties on the operation of the PT
PT-symmetric coupled resonators is also investigated using the time-domain
Transmission-Line Modelling (TLM) method. The BIE method is also used to study
the behaviour of an array of PT-microresonator photonic molecules.
