Infrared Camouflage Technology Based On Spectral Control Of Thermal Emission

Thermal emission is a natural and ubiquitous phenomenon in daily life,which propagates in the form of electromagnetic wave and functions as one of the heat transfer channels.With the rapid development of the nanophotonics,the thermal emission can be regulated by the photonic structures e.g.Fabry-Perot cavity,Tamm plasmon,photonic crystal,grating,and metasurface.The manipulation on thermal emission spectrum is an important part of thermal emission regulation,which has significantly high degree of freedom.The manipulation on thermal emission spectrum is crucial in energy and information applications,which is related to the control of radiative heat transfer and electromagnetic wave of thermal emission,respectively.The infrared camouflage is a particular application of manipulation on thermal emission spectrum,involving both employments towards energy and information.However,the current researches about infrared camouflage are limited to individual realization through regulation of either thermal conduction or thermal emission.When employed for infrared camouflage in high-temperature occasions,devices in current researches may suffer from insufficient camouflage due to extremely strong infrared signal of high-temperature objects.In addition,as the noble metals are extensively used in current researches,there are not only material failures for high-temperature infrared camouflage related to melting points,but also the incompatibility among camouflage in infrared and other spectral ranges due to intrinsic reflective properties of metals.Furthermore,in the current researches,the metasurfaces with complicated fabrications and expensive noble metal materials drastically increase the cost of infrared camouflage devices,preventing them from large-scale applications.In light of the above,in this thesis,the infrared camouflage is theoretically and experimentally studied by manipulation of thermal emission devices,which is combined to thermal insulators and the microwave absorptive metasurface,with regard to high-temperature application and multispectral-compatible application,respectively.For the high-temperature application,the scheme that combines the wavelength-selective emitter based on manipulation of thermal emission and the thermal insulator,is proposed and realize infrared camouflage through the simultaneous decrease of surface temperature and surface emittance.The temperature decrease is achieved by both the large temperature gradient in thermal insulator and the heat dissipation in non-atmospheric window for wavelength-selective emitter.The surface temperature is decreased to 410 K with the object temperature of 873 K,and the radiation temperature is decreased to 310 K,through the low emittance in the atmospheric window for wavelength-selective emitter and the low surface temperature.According to the calculation of lock-on range,the high-temperature infrared camouflage can effectively reduce the detection range by 50.9%compared to the conventional broadband low emittance materials.For the multispectral-compatible application,a layered device combining wavelength-selective absorber/emitter and microwave absorptive metasurface is proposed for multispectral camouflage for infrared,visible,lasers,and microwave spectral ranges.The multispectral camouflage realizes low emittance of 0.11/0.12 in mid-wave infrared/low-wave infrared,colors in visible range,absorptance of higher than 0.9 in microwave X-band,and absorptance higher than 0.7 at two lasers'wavelength,with the single anti-reflection surface ZnS layer along with the Ge/ZnS one-dimensional photonic crystal as the wavelength-selective absorber/emitter and the Cu-ITO-Cu structure as the microwave absorptive metasurface.And through the comparative experiments between normal-pressure,the enhancement of natural convection when coupled to radiation in non-atmospheric window is validated.The wavelength-selective emitter is designed and fabricated for manipulation of thermal emission.The infrared camouflage achieved by simultaneous low emissivity and low thermal conductivity as well as multispectral compatibility among camouflages for different bands are studied.With the combination between wavelength-selective emitter and thermal insulator as well as microwave absorptive metasurface,the high-temperature infrared camouflage as well as multispectral camouflage for infrared,visible,lasers,and microwave are realized,respectively.Based on the designs and the devices in this thesis,further researches on self-adaptive,wearable,or self-feedback infrared camouflage can be conducted.The development roadmap about combinative applications of the thermal emission manipulation for energy,fabrics and textiles,and artificial intelligence fields is prospected.