Past Achievements and Future Challenges in the Development of Infrared Antireflective and Protective Coatings

Abstract

Infrared (IR) antireflective and protective coating (ARPC) is crucial for the development of IR precision guidance and detection systems for practical applications, attracting significant attention from strong military powers worldwide. Extreme application environments require functional film to have high surface hardness, excellent stability, and good adhesion. Further, multispectral optical transmission demands extremely low absorption in the visible and far‐IR bands, adjustability of optical performance parameters, and optical antireflection in particular bands, and radar stealth requires a relatively low resistance. Herein, recent experimental progress on IR ARPC is reviewed and future opportunities are discussed. Based on the application environment and window substrate, various ARPC material systems, including diamond‐like C, Ge carbide, B phosphide, and oxides, have been developed. These systems are capable of fulfilling different application demands and demonstrate exciting application prospects. To promote the development of IR ARPC material technology, the basic characteristics, fabrication techniques, microscale structures, optical properties, mechanical properties, and development and applications of typical IR ARPC materials from a comprehensive and systematic perspective are presented.

SiO2/HfO2 Laser Film with Enhanced Protection and Antireflection for Sapphire Infrared Windows at High Temperatures

“…The higher the maximum phonon energy, the shorter the cutoff wavelength of the infrared spectrum. This makes the infrared window material less applicable at elevated temperatures; therefore, antireflection is highly indispensable. , However, there are different temperature variations of the refractive indices for sapphire, SiO 2 , and the HfO 2 films; therefore, there are some obvious differences in antireflection between SiO 2 and the SiO 2 /HfO 2 film for sapphire windows at high temperatures. The double-sided SiO 2 /HfO 2 films greatly improve the high-temperature infrared transmittance of the sapphire window in a wide wavelength range.…”

“…Progress in the preparation of large-sized sapphire (α-Al 2 O 3 single crystal) with high quality makes it an attractive infrared (IR)-transmission window candidate material. − However, in extreme military, metallurgy, and aerospace environments, sapphire windows may face further challenges such as harsh climates, flying sand, thermal shock, and high-power laser. Therefore, many issues should be considered for their practical application.…”

Periodic Al2O3 Nanohole Arrays on MgO (100) for a Low-Reflectivity External Cavity Fabry–Pérot Interferometer

“…Currently, multilayer composite thin-film coating is the most common approach to achieving AR. 10,11 However, the stability of the multilayer structures may be insufficient for hightemperature applications. With the development of photonics technology, interfaces can be designed with periodic subwavelength-scale structures, such as pillars, holes, pyramids, and cones.…”

“…Currently, multilayer composite thin-film coating is the most common approach to achieving AR. , However, the stability of the multilayer structures may be insufficient for high-temperature applications. With the development of photonics technology, interfaces can be designed with periodic subwavelength-scale structures, such as pillars, holes, pyramids, and cones. − The refractive index on both sides of the interface can gradually change using relief structures, avoiding light loss or reflection caused by abrupt refractive index changes without increasing the influence of diffraction.…”

Poly(Vinylidene Fluoride‐co‐Hexafluoropropylene) Films Filled in Iron Nanoparticles for Infrared Shielding Applications

“…The shielding materials are important for many commercial and military applications, including stealth technology, control panels DOI: 10.1002/marc.202300038 of electromagnetic interference, etc. [1,2] In particular, the infrared (IR) shielding materials gain more and more attention in the scientific community because they can act as the barriers or filters against IR radiation and resulting heating effects. [3,4] This unique property can be effectively used in the application like wearable IR shield, [5] solar filters, [6,7] solar collectors, [8] optical fibers, [9] stealth technology, [10][11][12][13] and so-called smart windows which aim to limit or increase the indoor temperature during summer or winter season, respectively.…”