Reflection of few-cycle x-ray pulses by aperiodic multilayer structures

We report on the numerical investigation of the reflection of extremely short (femto- and attosecond) x-ray pulses by multilayer structures (MSs). Periodic and aperiodic MSs are considered. We formulate the conditions whereby the reflection does not significantly change the pulse shape and length. The optimization of broadband aperiodic MSs from the viewpoint of the reflection of few-cycle pulses and the possibility of chirped-pulse compression are considered. It is shown that the power reflection coefficient can be appreciably higher than unity. Aperiodic MSs have been calculated which are capable of reflecting pulses comprising only three wave periods.