Contamination-resistant silica antireflective coating with closed ordered mesopores

Area of Science:

• Materials Science
• Optics
• Nanotechnology

Background:

• Traditional porous silica antireflective (AR) coatings for high power lasers suffer from transmittance decrease due to vacuum contamination absorption.
• The disordered pore structure of conventional coatings readily absorbs contaminants in high vacuum environments.

Purpose of the Study:

• To develop a contamination-resistant silica AR coating with enhanced transmittance stability in vacuum.
• To create a silica AR coating featuring ordered, closed mesopores for improved durability.

Main Methods:

• Fabrication of ordered mesoporous silica via evaporation-induced self-assembly using surfactant F127.
• Closure of mesopores using post-grafting with long-chain fluoroalkylsilane to impart hydrophobic-oleophobic properties.
• Characterization using grazing incidence small angle X-ray scattering (GISAXS), X-ray reflectivity (XRR), and nitrogen adsorption-desorption analysis.

Main Results:

• Successfully created silica AR coatings with ordered mesopores exhibiting Fmmm orthorhombic symmetry.
• Achieved low surface roughness, excellent abrasion resistance, and 100% transmittance on quartz substrate.
• Demonstrated exceptional vacuum stability with only a 0.02% transmittance decrease after one month of polydimethylsiloxane pollution.
• Obtained a high laser-induced damage threshold of 59.8 J cm⁻² for a 12 ns, 1053 nm laser pulse.

Conclusions:

• Developed a novel silica AR coating with closed ordered mesopores, offering superior contamination resistance and transmittance stability in vacuum.
• The hydrophobic-oleophobic nature of the closed pores prevents contaminant absorption, enhancing coating longevity.
• This approach provides a viable alternative for fabricating highly stable AR coatings for demanding applications like high power laser systems.