Optical coating with a thin-film is used to improve transmission, alter reflective properties or change the polarization (direction) of light that passes through an optical component. An optical coating may be a simple layer of metal such as aluminum, or it may be a complex dielectric coating formed of multiple thin layers of material, where the composition, thickness, and number of layers is carefully controlled for a precise result.

The Coating on the optical element is very important, which can improve the transmission, high reflection, etc. SUPERIOR® Optics offers all kinds of anti-reflective (AR coating), high reflective (HR Coating) and partial reflective (PR Coating) coating according to customer’s requirement. We can produce a wide variety of coatings from simple single layer AR coatings using MgF2 and mirror coatings to complex multi-layer dielectric coating. Typical types of dielectric coatings are BBAR, V-coatings, and Dual wavelength coatings.

SUPERIOR® Optics measure the coating spectral curves by Perkin-Elmer Lambda 900(UV/VIS/NIR) spectrophotometer for our coatings. The coating spectral curves measured by Perkin-Elmer Lambda 900 can be provided upon your request. We make coatings meet the Standard Mil Spec tests of Abrasion (Mil-C-675A), Adhesion (Mil-M-13508C), Hardness(MIL-M-13508C).

1. Anti Reflective Coating (AR Coating)

An anti-reflective coatings reduce unwanted reflection. A standard, uncoated component of glass will reflect approximately 4% light. A glass component that has an AR coating customized for the wavelengths of light transmitted may reflect less than 0.1%. We offer different dielectric anti-reflective coatings including broadband and narrowband options. Magnesium fluoride is a versatile and durable option. It comes in single-film or multiple-layer options.

2. Reflective Coating

A Reflective Coating will cause the surface it is applied to to reflect some or all of the light that hits it. Take a look at the glass optic that is uncoated and has a 4% reflectance. Metal coating can completely change the properties of an optic. Aluminum coating will reflect 88-92% visible light. Silver coatings can reflect up to 99% of far-infrared light (the reflection will be less in the visible and UV spectrum). A dielectric coating, if chosen correctly, could boost reflectivity as high as 99.9%. Dielectric mirrors are usually made up of two distinct layers. One layer has a high index, such as ZnS, TiO2, and the other one has a low index, like MgF, or SiO2. These dielectric coatings are highly reflective over a very specific wavelength range called the bandstop.

3. Polarizing Coating

A polarizing coat is formed by a thin layer of birefringent materials, or alternatively through interference effects within a multilayer dielectric coating. If desired, polarizers may be designed with an angle of incidence of 45 degrees to produce a beam that is reflected at 90 degrees. In certain situations, a polarizing layer on a lens can replace the polarizing prisms of an optical assembly.

4. Transparent Conductive Coating

A transparent conductor coating combines high transmittance of visible light with electrical conductivity. These coatings are used to protect the device aperture from electromagnetic interference or provide electrodes that allow light to pass. The resistivity of transparent conductive coatings is measured in ohms/square and can range from 4 to 1,000 ohms/square depending on the application. ITO (indium titan oxide) and AZO are two conductive options.

SUPERIOR® Optics uses a number of different methods for the production of high-quality optical coatings. These include plasma sputtering and ion beamsputtering as well as atomic layer deposition and evaporative coating.

Thereinto, the ion beam sputtering and atomic layer deposition provide the highest spectral performance, high durability and high repeatability; but the manufacturing process is slow and expensive. Evaporative deposition offers a more cost-effective solution, while plasma sputtering or plasma assisted magnetic sputtering provides a middle ground that is both high quality and low performance.

1. Ion Beam Sputtering

Ion beam sputtering (IBS) is a technique that uses a high-energy electric field to accelerate an ion beam, resulting in a kinetic energy between 10 and 100 eV. The ion blast hits the material source, and the ions from that material sputter on the optical surface. Upon contact, a dense film forms. Every step in this process is monitored and controlled precisely, resulting in a uniform coating that is designed to meet design parameters and specifications. IBS coatings may even be smoother than the original substrate. This method is used to create “super mirrors”, coated mirrors that have a reflectivity greater than 99.99%.

2. Atomic Layer Deposition (ALD)

Atomic Layer Deposition (ALD) is to be coated will often be placed in a chamber with a high temperature and vaccum. Gas pulses are used to deliver the coating substance. The vacuum chamber is evacuated between each pulse to prepare for the next. This method offers a high degree of control over the thickness of the material layers and their composition. It also allows for uniform coating of optics of any shape. This method has only one negative aspect: it is expensive and slow.

3. Evaporative Deposition

Evaporative deposition is a fast process that produces medium high layer density and a stable spectral performance. It can be used on almost any substrate geometry, and has medium to high layer smoothness. One type of evaporative deposition is called ion assisted electron-beam evaporative deposition, and is performed in a vacuum chamber where an electron gun bombards and vaporizes source materials.

While this method is not ideal for ultra-low or ultra high reflection coatings, it is a good choice where low cost and flexibility are more important than high performance. Since it can be conducted at low temperatures (20-100 C) it may be a good choice for temperature-sensitive substrates.

4. Plasma Assisted Reactive Magnetron Sputtering

In plasma assisted reactive magnetron sputtering (PARMS), glow discharge plasma, confined by a magnetic field to an area near the target, accelerates positive ions onto the target deposition material. The atoms are ejected, which coat the optical surface. This process is efficient even with low chamber pressures, allowing it to be carried out in a short time.

PARMS has a higher throughput and is more repeatable than the evaporative process, even though it is not as repeatable. It is a good choice for a fluorescence filter because it balances good optical performance with high volume throughput.

SUPERIOR® Optics performs rigorous metrology tests on each component after it has received an optical coating to ensure that it works exactly as intended. We use spectroscopes of research-grade to characterize the reflectivity properties of coatings, from UV to Far Infrared. We also use state-of-the art metrology equipment such as optical diode and laser sources, power meters and detectors to quantify the properties of each component.

Optics coatings are essential for fiber optics, as they increase strength, reduce fatigue and improve attenuation. These coatings protect your device from damage and can extend its lifespan. Standard communication fibers are coated with a UV-cured polymer acrylate, usually in two layers. A soft primary layer and a hard secondary layer. Other specialty coatings are fluorescent materials, sensing agents, silicone, sapphire nitrides metals and carbon. Metal and carbon thin coatings are also suitable for use in combination with polymer coatings.

SUPERIOR® Optics has the capability to produce and coat high-performance fiber optics according to your specifications. We have clean room facilities, sensitive equipment and a highly controlled process to produce micro-optical products. All our fiber optics leave our factory after being carefully inspected.

The final properties and function of a thin film coating are dependent on the materials used to create the thin layers, especially their refractive index. The interference effects of thin film coatings can be completely altered by changing the thickness of the layers and the number. The optical thickness of every layer is very important for precision coatings.

Your budget, the wavelength of light in your environment and the work environment will all influence the design of your optical coating. Our team of designers has years of experience with coating technologies and would be delighted to assist you in determining the custom optical coatings which best suit your application.