Sharif Digital Repository

We study the phenomenon of parametric amplification and instability in the context of time-varying electromagnetic structures, particularly dielectric slabs with periodically modulated permittivity. These structures show particular promise inasmuch as they are capable of very large amplifications when illuminated by an electromagnetic wave of half the modulation frequency. Successive studies have corroborated this finding but none have yet been able to ascertain the nature of amplification in such devices. On top of that, the problem of instability in time-periodic slabs has either been disregarded altogether or it has been subjected to loose analysis, leading to mere speculations which are...