AAWSAP DIRD, Metamaterials for Aerospace Applications, April 2010

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than the zeroth one. This confirms the recently predicted effect that for IPMs one can
indeed observe a very counterintuitive effect: sub-diffraction waves can indeed
propagate with less loss than the diffraction-limited ones.
The second milestone involves demonstrating the possibility of observing the
interference of sub-diffraction electromagnetic waves inside the IPM using the two­
beam/two-detector technique. Figure 10 demonstrates this interference pattern which
reveals the phase advance of the sub-diffraction waves inside the IPM. While we have
so far demonstrated the interference between the first Fourier component of the grating
(sub-diffraction) and the zeroth Fourier component, we see the possibility of interfering
even more sub-diffraction waves (2nd and 3rd).
Interference scan, 10.800 micro11s
•
•
10
12
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I°' +-t---+---
----1-1,__,__
_
+f-_,___
l-f--t-i
lnst-t-l---l-+--l-l--,f+--1- -1--t- l--l-i
I DA ,__,,_,__
.,._1--,.-1--1-,
Figure 13. (Left): Experimental Setup for 2-Beams/2-Detectors Interferometric Measurement in Our
Lab. (Right): Preliminary Experimental Results : infrared intensity on two detectors (red and black lines) are
(i) different from each other; (ii) have a sinusoidal dependence on the delay line position (in microns), which is
equivalent to the phase delay between the two beams; (iii) are shifted in phase by the amount equal to twice the
phase difference between the pt order (sub-diffraction) and 0th order (radiation zone) Fourier components of the
bottom grating. Measurements taken at J..= 10.8 µm and J..= 11.3 µm.
With these two milestones established, it is now possible to conduct true sub­
wavelength imaging experiments using two (or more) far-field detectors and jointly
processing their inputs.
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