AAWSAP DIRD, Metamaterials for Aerospace Applications, April 2010

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Our implementation of the FSL utilizes an 1PM whose dielectric permittivity tensor is
anisotropic and contains positive and negative components: c1_ > 0,c11 < 0, where parallel
refers to the !PM/object interface. We have already fabricated such IPMs using SiO2­
SiC-SiO2 multi-layer, and are investigating other approaches involving selectively-doped
semiconductor multi-layers similar to the ones used by Gmachl's group at Princeton.
SiO2-SiC-SiO2 multi-layers are produced in-house (with SiC films shipped by Professor
Ferro from University of Lyons, France). The main function of the 1PM is to propagate
sub-diffraction waves ( "ii > wl c) with as little decay as possible. That happens because
these sub-diffraction waves are no longer evanescent: k1 ~ -kI~&11 I &1- > 0. It is
demonstrated experimentally that there exists a frequency range for which sub­
diffraction waves propagate through the 1PM with less attenuation than the radiation­
zone waves ( "ii < w/ c ), see Figure 11.
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Figure 11. First Experimental Demonstration of Propagating Sub-Diffraction Waves in the 1PM. (Left):
Experimental setup demonstrating how sub-diffraction waves are launched into the 1PM using FIB-fabricated sub­
wavelength grating. Because the periods of the bottom ("launching") and top ("transforming") gratings are
different, far-field observation of different harmonics of the bottom grating is enabled. (Right): Experimental
results: the first sub-diffraction harmonic of the grating (green line) becomes stronger than the zeroth radiation-
zone harmonic of the grating (blue line) in the region where£1- > 0, &11 < 0 .
Once sub-diffraction waves propagate through the 1PM, they can diffract on the image­
releasing grating (see Figure 10) and be radiated out into the far field. A detector array
can be used to collect the signal and reconstruct the image. Unfortunately, different
wave numbers k 11 of the object are directed into the same detector and produce an
ambiguity in extracting their respective amplitudes A(k11 ). This ambiguity is illustrated
by Figure 10: wave numbers k1 = tik + 21r ID and k2 = M + 41r ID are directed to the
same far-field detector. Simply put, a single number (intensity of light with the wave
number tik < w I c incident on the detector) is insufficient for determining two scattering
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