Abstract
We introduce an optimized aperiodic multilayer structure capable of broad angle and high temperature thermal emission over the 3 μm to 5 μm atmospheric transmission band. This aperiodic multilayer structure composed of alternating layers of silicon carbide and graphite on top of a tungsten substrate exhibits near maximal emittance in a 2 μm wavelength range centered in the mid-wavelength infrared band traditionally utilized for atmospheric transmission. We optimize the layer thicknesses using a hybrid optimization algorithm coupled to a transfer matrix code to maximize the power emitted in this mid-infrared range normal to the structure’s surface. We investigate possible applications for these structures in mimicking 800–1000 K aircraft engine thermal emission signatures and in improving countermeasure effectiveness against hyperspectral imagers. We find these structures capable of matching the Planck blackbody curve in the selected infrared range with relatively sharp cutoffs on either side, leading to increased overall efficiency of the structures. Appropriately optimized multilayer structures with this design could lead to matching a variety of mid-infrared thermal emissions. For aircraft countermeasure applications, this method could yield a flare design capable of mimicking engine spectra and breaking the lock of hyperspectral imaging systems.
Highlights
Infrared countermeasures break or jam seeker-missile signal locks on fixed-wing or rotor aircraft
We designed a thin-film structure composed of alternating layers of silicon carbide and graphite of aperiodic thicknesses above a semi-infinite tungsten substrate
We used a hybrid optimization algorithm consisting of a global stochastic micro-genetic algorithm coupled to a local deterministic algorithm to optimize structural dimensions for maximum emitted power in the 3–5 μm wavelength range
Summary
Infrared countermeasures break or jam seeker-missile signal locks on fixed-wing or rotor aircraft. It has been shown that optimized multilayered structures exhibit properties similar to more complex and harder-to-fabricate two- or three-dimensional structures.[5] Here, we optimize the layer thicknesses using a transfer-matrix code[6] to maximize the power emitted in the 3–5 μm wavelength range in the normal direction. This wavelength range corresponds to both the mid-infrared atmospheric transmission window and the combined aircraft engine and fuel combustion spectra. These are typically applications in the visible to near infrared range and largely ignore the mid-infrared atmospheric transmission windows.[3]
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