Non-Hermitian Wave Transport with Applications to Limiters and Isolators

Non-Hermitian wave transport has attracted a lot of attention during the last ten years, mainly because of its applications in on-chip photonic circuitry. The underlying principle of this subfield of wave transport is the violation (induced or spontaneous) of the time reversal symmetry via lossy mechanisms. When other symmetries are also involved in the design of such circuits (e.g. chiral, mirror, etc.), novel phenomena, such as topologically protected states, might emerge. In this thesis, we utilize time reversal symmetry and its violation along with other symmetries in order to propose a new type of reflective photonic limiters and asymmetric valves. The former family of devices are useful for protection of sensitive sensors from high power/fluence incident radiation, while the latter guides light in a directional fashion, thus providing the basic element for on chip isolators, circulators etc.