Universal role of Lorentzian solitons in structures with photonic bandgaps

Summary form only given. Periodic dielectrics exhibiting photonic bandgaps (PBGs) attract a lot of interest from both fundamental and applicative point of view. One-dimensional PBG structures, are best suited to fully understand the effect of nonlinearity. For example, bistability, self-pulsing, modulation instability and gap-solitons have been first predicted and observed in Bragg gratings with Kerr nonlinearity. Here, we show that these PBGs possess in common a particular type of gap solitons which do not decay exponentially, but rather exhibit Lorentzian intensity profile (and a phase chirp).