Infrared Dome AR Coating, DLC Coating and Other Functional Coatings

Overview of Infrared Dome Coatings

For infrared domes and optical windows made from CVD ZnS, CVD ZnSe and sapphire, AR coating and DLC coating are the most widely adopted two thin-film solutions. Besides these two mainstream options, there are multiple other functional coatings to meet special optical, environmental and industrial requirements. Felix Optical Glass supplies full custom coating services for infrared optical components.

AR Coating & DLC Coating (Mainstream IR Dome Coatings)

Other Available Coatings for Infrared Domes

1. Single-layer AR / Multi-layer Broadband AR Coating

Single-layer AR is cost-effective and optimized for one fixed wavelength. Multi-layer broadband AR stacks multiple dielectric films, delivering high transmittance across a wide infrared spectrum for multi-spectral thermal systems.

• Single-layer AR: Budget option for single-band infrared equipment
• Broadband multi-layer AR: Ideal for multi-spectrum thermal cameras
• Limitation: Thin dielectric film, vulnerable to sand scratch without top protective coating

2. Anti-fouling / Hydrophobic Coating

Anti-fouling hydrophobic coating is a thin top functional layer, usually applied over AR coating. It repels water droplets, oil, dust and salt spray, greatly reducing surface contamination for coastal and underwater infrared domes.

• Hydrophobic & oleophobic, self-cleaning effect
• Reduce salt buildup for offshore optical windows
• Limitation: Low hardness, cannot withstand heavy sand erosion

3. Oxide Hard Protective Coating

Metal oxide hard coating serves as an alternative protective coating to DLC. It offers moderate scratch resistance and low infrared absorption, which makes it suitable for some laser-grade ZnSe optics where DLC may introduce extra absorption.

• Stable chemical resistance against humidity and weak corrosives
• Lower IR absorption than DLC on laser ZnSe substrates
• Less abrasion resistance compared with DLC

4. IR Bandpass Filter Coating

Bandpass filter coating selectively allows target infrared wavelength to pass and blocks out-of-band stray light. It improves signal-to-noise ratio for precision IR sensing and spectroscopy instruments.

• Custom wavelength band design available
• Suppress unwanted background light noise
• Often combined with AR coating for better optical throughput

5. Metallic Reflective Coatings (Au / Ag / Al)

Gold, silver and aluminum metallic coatings are high-reflection films instead of transmission coatings. They are used for infrared mirrors and beam reflectors, not transparent protective domes for thermal cameras.

• High reflectivity within infrared wavelength range
• Additional protective overcoat prevents metal oxidation
• Not applicable for IR dome windows that need light transmission

Coating Stack Combination Rules

Multiple coatings can be stacked to satisfy compound requirements. Common combinations: AR + anti-fouling topcoat, multi-layer AR + oxide hard coating. Coating stacking must strictly control film stress, especially for thin-wall hemispherical domes, to avoid surface figure distortion. Our optical engineers will evaluate substrate compatibility before coating production.

Substrate Compatibility Summary

• CVD ZnS: Compatible with nearly all coating types, most versatile substrate
• CVD ZnSe: AR coating series preferred; hard coatings such as DLC need pre-evaluation to avoid absorption
• Sapphire: Supports all above coatings, excellent choice for deep-sea high-pressure viewports

Coating Quality Inspection

All coated infrared optical parts will pass spectral transmittance or reflectance test, surface defect inspection, coating adhesion test and environmental aging test. Coating test certificates and spectral data sheets can be provided for OEM, industrial and aerospace customers.

Get Custom Coating Quote for Infrared Domes

Please provide your substrate material, dome dimensions, target wavelength, working environment and coating requirements. Our coating engineers recommend the best coating scheme. Both prototype samples and mass production orders are acceptable.

FAQ: Infrared Dome Coatings

1. Can anti-fouling coating replace DLC coating?
No. Anti-fouling coating repels water, oil and salt, but lacks high hardness. DLC is designed for sand and scratch abrasion protection.

2. Can we combine bandpass filter coating with AR coating?
Yes. The stack integrates wavelength filtering and anti-reflection functions for precision infrared detection systems.

3. Is gold coating used for thermal imaging protective domes?
No. Gold coating reflects infrared light. It is used for IR mirrors, not transparent camera domes.