Modulational transparency and femtosecond pulse train in Bragg reflectors with time-varying dielectric constant

A theoretical study is conducted to investigate the nonlinear properties of a one-dimensional (1D) periodic stratified structure with time-varying dielectric constants. When the dielectric constant is modulated temporally, the distributed Bragg reflector exhibits different throughputs depending on the modulation amplitude. Below or at the critical value, a periodic and stable femtosecond pulse train is generated; above this critical value, the modulational transparency is observed, as the reflectivity decreases rapidly, so that all incident radiation is completely transferred through the layered media. When the layer number is up to 15, the pulse train generated at the critical value is periodic with perfect reflectivity and zero rejection. These excellent optical properties may enhance the potential applications of the 1D periodic stratified structure in optical switches and laser optics.