Selective Emitter with Engineered Anisotropic Radiation to Minimize Dual-Band Thermal Signature for Infrared Stealth Technology.

Selective emitters comprising plasmonic resonators have been exploited for cooling devices or infrared stealth technology. While selective emitters have been designed using odd-order resonances, even-order resonances also emit anisotropic thermal radiation signals. Thermal radiation by even-order resonances in selective emitters can be experimentally detected by thermal imaging cameras, and such thermal emissions often degrade the observability of infrared detectors, rendering them inapplicable to infrared stealth technology. Here, a selective emitter with extremely low thermal radiation signature in a dual-band range, a detection range by an infrared detector, is proposed with engineering anisotropic thermal radiation by even-order resonances. To minimize infrared signature in a dual-band range, the characterization of even-order resonances of gap plasmon metasurfaces is achieved based on vectorial diffraction within a relative error of 10%. Thermal radiation by even-order resonance has been shown to be highly directional and can be experimentally measured using mid-wave infrared images. Based on model prediction, the proposed selective emitter reduces mid-wave infrared signatures and long-wave infrared signatures by factors of 37.95 and 38.06, respectively, compared with those of blackbody surfaces. In addition, numerically confirmed thermal signature reduction and captured mid-wave infrared images indicate excellent thermal camouflage performance of the selective emitter with background medium. Thus, the characterization of even-order resonances provides a basis for the design of metasurfaces that can be employed for multispectral applications, especially infrared stealth technology.