Spectral modification of array truncation effects in infrared frequency selective surfaces

Infrared frequency selective surfaces (FSS) are widely used in quasi-infinite, planar configurations; however, applications for finite arrays exist as well. Here, a square loop infrared FSS was designed with an infinite array resonance near 10 μm when illuminated at 60° off-normal. Along with the quasi-infinite array, a patterned area containing finite arrays of 7 × 7 square loops of this design was fabricated and characterized to have a resonance which was blue-shifted due to the effects of truncation. To counteract the effects of truncation, two geometrically modified arrays of 7 × 7 square-loop elements were designed and fabricated to shift the resonant wavelength approximately back to that of the infinite array.