Enhancing The Transmission Of Diffracted Light In Sub-Wavelength Apertures

Anomalous transmission through sub-wavelength aperture metamaterials, frequency selective surfaces and sub-wavelength sized aperture arrays has been a topic immense interest in the present decade. The ability to manipulate electromagnetic energy as it propagates through a metamaterial has ushered in a an age of sub-wavelength optical devices. Optical devised are prone to diffraction and back scattering. Diffraction effects inhibit the transmission performance of metamaterial sub-wavelength films. Depending on the application, back scattered light could be beneficial or undesirable. A method to reduce back scattered light is explored in this paper. This method involved placing sub-wavelength square apertures within a film to suppress the diffraction. Coupling of the fields between the apertures was observed in one of the studied structures. There is a spatial relationship between the distance separating the apertures and the coupling of the light. To characterize the coupling behavior and thereby reduce the far-field back scattering of light, more apertures were placed in various positions within the unit cell. This enabled reduction of the back scattering thereby, enhancing the forward transmission of light. It was found that populating the unit cell with more apertures resulted in a higher transmission. Increasing the spacing between the apertures resulted in couple cavity effects between the apertures. This effect is due to the fact that the apertures have a wider bandwidth hence broader transmission channels which aid light transmission rather than light scattering or reflection.