Investigation of electromagnetic diffraction at any distance from an infinite slit is presented for slit widths 0.5 wavelength and wider. Plane-wave incidence of arbitrary two-dimensional angle in a plane perpendicular to the edges of the slit is used. Infinite conductivity is assumed. The contribution of this work is in the near-field and medium-slit-width regions, where no numerical results have been given. One obvious application is high-resolution, contact or near-contact, printing.
BURN JENG LIN, "Electromagnetic Near-Field Diffraction of a Medium Slit," J. Opt. Soc. Am. 62, 976-981 (1972)