Optical Coating Explained: AR, BBAR, and HR Coatings — How to Choose the Right One?
optical coating
8/3/20261 min read
When selecting optical components, many engineers focus on material, surface quality, and dimensions. However, the optical coating is often the factor that determines the final system performance.
A high-quality optical surface without the correct coating may still result in unnecessary reflection, reduced transmission, and lower system efficiency.
So how should engineers choose between AR, BBAR, and HR coatings?
Anti-Reflection (AR) Coating: Improving Transmission
Every uncoated optical surface reflects a portion of incoming light.
For example, common optical glass can reflect approximately 4% of visible light at each air-glass interface.
AR coatings are designed to reduce these reflections and increase transmission.
Typical applications include:
Imaging lenses
Optical windows
Cameras
Laser systems
Single-layer AR coatings such as MgF₂ are commonly used for specific wavelength ranges, while multilayer AR coatings provide higher performance over wider wavelength bands.
Broadband AR (BBAR): Wider Wavelength Performance
Many optical systems operate across multiple wavelengths.
Broadband AR coatings are designed to maintain low reflection over a wider spectral range.
They are commonly used in:
Machine vision systems
Imaging equipment
Scientific instruments
Multi-wavelength optical systems
The wider the required wavelength range, the more complex the coating design becomes.
High Reflection (HR) Coating: Maximizing Reflection
Unlike AR coatings, HR coatings are designed to maximize reflection.
They are widely used in:
Laser mirrors
Optical resonators
Beam steering systems
The coating design must consider:
Operating wavelength
Angle of incidence
Polarization
Laser power
A Common Optical Procurement Mistake
One common mistake is selecting a coating only by name.
For example:
"AR coating" does not define the complete requirement.
A proper coating specification should include:
✔ Wavelength range
✔ Angle of incidence
✔ Reflection/transmission requirement
✔ Polarization requirement
✔ Environmental conditions
Engineering Takeaway
The best optical coating is not always the most expensive one.
The correct coating depends on:
Application
Wavelength
Optical performance requirements
Cost considerations
A properly selected coating can significantly improve system efficiency while avoiding unnecessary expense.
At Positive Optics, we provide custom optical components including lenses, windows, filters, mirrors, and prisms with application-specific coating solutions.
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