Theoretical study of XUV pulse shaping due to the modulation of an IR pulse in macroscopic systems

Abstract Propagation effects are widely recognized as the origin of complex features observed in macroscopic absorption spectra. Here, we examine the evolution of spectral reshaping driven by laser-imposed initial phase modulation during pulse propagation. We present an analytical framework that elucidates the physical mechanism underlying the emergence of these propagation-induced spectral structures, and validate it through numerical simulations. Our results reveal that both the peak position and maximum absorption can be precisely tuned by controlling the atomic density, propagation length, and initial phase. Notably, under specific conditions, a designated frequency component of the extreme ultraviolet spectrum can be completely suppressed, enabling off-resonance perfect absorption.