Modelling pulse propagation through homogeneous and inhomogeneous dielectrics

摘要

A general concept based on harmonic decomposition of pulses has been introduced to model ultra short pulse propagation through homogeneous and inhomogeneous dielectrics. This include propagation through free space, apertures and lens systems. This approach permits us to consider pulses of any arbitrary spatial and temporal characteristics. The pulse characteristics are found to be affected by angular and material dispersion. A computationally efficient method for the proper sampling of spectral phase has been introduced which requires only a minimum number of harmonic fields for the simulation. In the case of free space propagation, pulses maintains their shape but experience temporal and spectral shifts whose magnitudes depends on angular dis-persion(diffraction angle). The pulse broadens, becomes asymmetric and chirped in dispersive media because of group velocity dispersion and higher order dispersion in the media. The pulse broadens due to radially varying group delay and group delay dispersion on propagation through focusing elements. The pulse energy at the focus is affected by the interplay of spherical and chromatic aberration by distributing the pulse energy over a large region on the axis.