Effects of Singular Dispersion Relation on Amplification in Electromagnetic Periodic Structures

The goal of the project was to develop concepts and theory, and to indicate possible benefits in modern technology, associated to singular dispersion relations for electromagnetic EM fields that either evolve in time in resonators or propagate in waveguides, focusing on spectral singularities and exploring the effect of gain. The UC Irvine research team has linked this fundamental research to various important applications from microwave to optical frequencies, like oscillators, antennas, amplifiers, lasers, sensors, etc. The spectral singularities investigated under this contract are referred to as exceptional points of degeneracy EPDs since they are all about a degeneracy point in a parameter space describing the spectral dispersion of electromagnetic fields either evolving in time or propagating in space. The UCI group has classified EM structures that develop EPDs of various orders into four categories, in relation to gain and losses and spacetime invariance or periodicity. The UCI group provided different examples of systems that lie under each category.