Nanoporous antireflection coating for high-temperature applications in the infrared

Area of Science:

• Materials Science
• Optical Engineering
• Nanotechnology

Background:

• Antireflection (AR) coatings are critical for optical systems, preventing performance degradation due to surface reflections, especially at steep angles of incidence (AOIs).
• Operational demands for optical systems often involve extreme conditions, including high temperatures and steep AOIs, posing significant challenges for conventional AR coatings.
• Nanoporous coatings made from high-temperature-tolerant materials present a viable solution for AR coatings under harsh environmental conditions.

Purpose of the Study:

• To develop and characterize nanoporous AR coatings with high-temperature tolerance and wide AOI performance.
• To investigate the thermal stability and optical performance of novel AR coatings under demanding operational parameters.
• To enable the extended operation of optical technologies in extreme temperature and steep angle environments.

Main Methods:

• Deposition of nanoporous silicon dioxide (SiO2) and hafnium dioxide (HfO2) coatings on a sapphire substrate using oblique angle deposition by electron beam evaporation.
• Evaluation of coating thermal stability in a controlled high-temperature environment up to 800°C.
• Measurement of optical performance, specifically power reflection reduction, at various AOIs up to 70° for a design wavelength of 1550 nm.

Main Results:

• The developed nanoporous coatings exhibited remarkable thermal stability, maintaining integrity and performance at temperatures up to 800°C.
• Significant reduction in power reflections was achieved, with performance optimized for AOIs up to 70° at a 1550 nm wavelength.
• The chosen materials (SiO2 and HfO2) and deposition technique (oblique angle deposition) proved effective for creating robust and high-performance AR coatings.

Conclusions:

• Nanoporous SiO2 and HfO2 coatings deposited via oblique angle deposition offer a promising solution for AR coating applications in high-temperature and steep AOI environments.
• These findings pave the way for enhanced reliability and performance of optical systems operating under extreme conditions.
• The developed AR coatings are suitable for demanding applications such as solar cells, laser optics, and optical windows operating at elevated temperatures and wide angles.