Detailed structure of femtosecond and sub-femtosecond pulses diffracted by a nanometre-sized aperture

The spatial structure of ultra-short (femtosecond and sub-femtosecond) pulses diffracted by a sub-wavelength (nanometre-size) slit-type aperture in a perfectly conducting thick screen is studied in detail. The near- and far-field distributions of the electromagnetic field amplitude and energy flux of the wavepacket having the central wavelength in the visible spectral region are found numerically by solving the Neerhoff and Mur coupled integral equations. The computations show that the shape deformation, temporal/spatial broadening and superluminal behaviour of the pulse are the main effects that influence the spatial and temporal capabilities of the near-field optics, in which the pulse passing through the aperture is used to provide nanometre spatial resolution together with fs or sub-femtosecond temporal resolution.