Coating

Coatings are applied to lenses and other optical substrates to modify optical properties such as transmission and reflection. This is essential for optimizing the performance of everything from camera lenses to telescope mirrors. At JML, we utilize advanced in-house coating equipment and techniques to customize optical components for a range of applications and environments.

Coating Types

Using various coating types and techniques, JML can manipulate an optical surface’s reflective properties to improve its functionality in the intended application. Our coating options include:  

Dielectric Coatings

Dielectric coatings are thin-film coatings made from one or more layers of polymers, ceramics, metal oxides, or other non-conductive materials. Depending on the desired optical properties, the coating can include anything from a single layer of material to as many as 100 layers deposited in various complex sequences. The types and sequences of materials in a dielectric coating influence the reflectivity of the coated surface through optical interference.

Depending on the type of dielectric coating used, an optical surface’s reflectivity can be increased or decreased for individual or multiple wavelengths of light. Dielectric coatings are generally classified into the following categories:

• Reflective. Reflective dielectric coatings create a mirror-like surface with higher reflectivity than most metallic mirror coatings. Capable of reflecting high-energy-density laser beams, these coatings are commonly used in high-power laser systems. A well-designed multi-layer dielectric coating is generally better suited than reflective metallic coatings for handling these high laser power densities.
• Anti-reflective. Anti-reflective dielectric coatings reduce a surface’s reflectivity to near-zero, enabling a maximum transmission of light through the optical surface. Broadband anti-reflective dielectric coatings can be produced with relatively few layers.
• Bandpass filters. Dielectric coatings can also be designed to allow a specific wavelength or narrow range of wavelengths to be reflected while permitting the passage of others. Composed of many layers, these types of coatings are used to create optical components known as spectral beamsplitters.

Mirror Coatings

A mirror coating is a reflective optical coating that can be customized to reflect almost all incident light or a certain percentage of incident light. Broadband mirrors, generally coated with metal, provide high reflectivity across a broad spectral region. In contrast, partially reflective mirrors—also known as partial mirrors or beamsplitters—provide partial reflectivity over a broad spectral region. 

Coating Process

To ensure maximum coating adhesion, each optical component must be thoroughly inspected and cleaned before starting the application process. Several technologies can be used to apply the coating, all of which involve vaporizing the coating material. The dielectric or metal layers are applied within a specially designed heated vacuum chamber. Once vaporized, the coating is deposited onto the optical surface in extremely thin, uniform layers.  

Applications and Industries

Dielectric and mirror coatings are useful across several industries and applications:

Dielectric Coatings

At JML, our dielectric coatings are used in a range of optical assemblies, including:

• Telescopes
• Spectroscopes
• Gene sequencers
• Blood analyzers
• Weapon sights
• Semiconductor wafer inspection equipment

Mirror Coatings

Our mirror coatings are commonly used to create:

• Telescope mirrors. In telescopes, a series of mirror-coated optical surfaces allow light to be collected, reflected, and focused to create a magnified image.
• Turning mirrors. To fit a long optical system into a compact space, turning mirrors set between other optical elements can redirect and fold the path of the light beams.
• Collimating mirrors. Collimating mirrors are curved, reflective surfaces that produce collimated beams of light by reflecting the light from a point source.

Why JML

With over 40 years of experience in optical system design and fabrication, JML has the expertise and resources to create high-quality custom optical solutions for nearly any application. We maintain eight onsite coating chambers, allowing us to provide both start-to-finish optical system manufacturing as well as coating-only services. Our coating experts work with a wide range of dielectric and mirror coatings on various substrates.

Depending on the customer’s needs, we also provide:

• Design support
• Manufacturability assessment and performance optimization
• Lens assembly optimization

To learn more about our optical coating services and other capabilities, please contact us today.