Significance With the diversified development of infrared detection technology, the demand for infrared stealth technology is increasingly urgent. Infrared stealth technology aims to effectively control the infrared signature signals of weapons and equipment, reduce the operating range of enemy infrared detection systems, improve survival ability, penetration ability, and combat effectiveness. However, traditional infrared stealth technology is facing serious challenges of multi-band detection and multi-functional compatibility, making it of great significance to study the infrared stealth technology of micro-nano optical structure. Sub-wavelength micro-nano optical structures based on local resonance mechanism greatly enrich the modulation of light transmission behavior. They can be state-of-the-art in material and structure design for infrared radiation, so as to meet the demand of ideal emissivity spectrum for infrared stealth. It is foreseeable that infrared stealth technology based on the optical micro-nano structures will transform traditional infrared stealth technology and provide point-to-point spectral design for the multi-aspect demand, which makes the research progress of micro-nano optical structure infrared stealth technology meaningful.
Progress Focusing on the progress of infrared stealth technology, this paper introduces the basic principles of thin film absorber, metal surface plasmonic, tunable absorber based on phase change materials (PCMs), and intelligent design for spectral response firstly. For example, the PCMs are widely used in tunable infrared absorbers by regulating resonance wavelength and changing infrared emissivity without the structural changes (Fig.4). And the innovatory field of the intelligent design has recently been transforming conventional micro-nano optical structure and allowing for the discovery of unorthodox optical structures via computer algorithms rather than engineered "by hand" (Fig.5-6). Secondly, the development status of optical micro-nano structure infrared stealth technology in the past decade is introduced. As an application technology driven by demand, infrared stealth technology faces many challenges such as multi-spectral compatibility, multi-functional integration, and complex changing environments. With the deepening optical micro-nano structures research, the application of infrared stealth technology has been expanding and showing the following new characteristics. (1) In order to deal with the thermal radiation detection of infrared atmospheric transparent window bands, infrared stealth technology is developing from single-band towards the multi-band infrared stealth; (2) On the basis of multi-band infrared stealth, balance and comprehensive design with infrared laser, visible light, radar and other multispectral stealth are required; (3) A new infrared stealth technology is developed that combines multiple functions such as thermal management, infrared sensor, and radiation regulation; (4) Adaptive infrared stealth technology is developed that integrates new materials such as phase change materials, two-dimensional materials of graphene, and vanadium oxides. To this end, the spectral tailoring design achieved through optical micro-nano structures endows infrared stealth technology with more new possibilities, including multispectral infrared stealth technology, multifunctional infrared stealth technology, and adaptive infrared stealth technology. According to the different requirements of multi-spectral compatibility, this paper summarizes the possible requirement of multispectral infrared stealth technology and current development status (Fig.7). Through the comprehensive survey, this paper reveals four development trends of micro-nano optical structure infrared stealth technology: multispectral compatibility, multi-function integration, large-area fabrication, and adaptive infrared stealth system.
Conclusions and Prospects During the last decade, the micro-nano optical structure infrared stealth technology has made dramatic development. The multispectral infrared stealth technology has been extended from the single-band to the multi-band infrared stealth technology which is compatible with visible band, laser, and microwave. The multifunctional infrared stealth technology has been considered to integrate the thermal management, infrared encryption and infrared sensor, the adaptive infrared stealth technology has been widely studied in the dual-band infrared transparent atmosphere window by flourishing research of smart materials. The research of this paper aims to provide some reference for the infrared stealth technology of optical micro-nano structures in the future. It is expected that optical micro-nano structures will provide a promising way for the more multispectral, more versatile, and more adaptive infrared stealth technology.
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