ISO 9001 - AS 9100 - ITAR Standard & Custom Optical Filters and Coatings

Optical Coating Capabilities


What is an Optical Filter Coating?

An optical thin film coating is one or more thin layers of material deposited on a substrate material suitable for a particular application, which alters the way in which light reflects and transmits. One type of thin film coating is an antireflection coating, which reduces unwanted reflections from surfaces, and is commonly used on lenses, windows, and imaging optics. Another type is a high-reflector coating which can be used to produce mirrors and dichroics that reflect and transmit light as well. More complex thin film coatings exhibit specific spectral responses over some range of wavelengths, and can perform multiple functions, allowing for the production of complicated thin film optics for the the defense industry. One of the most common types of thin film coatings are band-pass filters that only transmit a certain wavelength band and block others. The width of such a filter is expressed in the wavelength range it lets through, and can be anything from much less than an angstrom to a few hundred nanometers.


Andover has a variety of optical coating thin film deposition technologies at its disposal, providing customers with solutions tailored to their specific applications. Technologies include:

We can design and manufacture coatings to meet your most demanding requirements. Range of Wavelengths from 193nm to 14 microns, on a wide variety of substrate materials including BK-7, filter glass, borosilicate glass, Silicon, Germanium, Sapphire, Fused Silica, Calcium Fluoride, Zinc Selenide, Zinc Sulfide, and more.

All Andover chambers are internally custom-built or modified turnkey systems that are computer-controlled, and use the latest deposition techniques.


We have an extensive back-catalog of optical coating formulas for a variety of wavelength ranges and substrate materials from hard oxide and crystalline materials to fluorides and metals. Our thin-film coatings employ oxide and fluoride dielectric multilayer coating materials including MgF2, SiO2, Ta2O5, HfO2, and dozens more. Our current coating line-up covers a nominal wavelength range from 193nm - 14µm.

Coating Types

  • Anti-reflective coatings
  • High reflective coatings
  • Partially reflective coatings and Dichroics
  • Non-polarizing or limited-polarizing separation coatings
  • Bandpass coatings for the UV, visible, and infrared
  • Beam splitter coatings for the UV, visible, and infrared
  • Neutral density filters
  • Protective and enhanced aluminum, silver, and gold coatings 

We have the unique ability to provide a diverse range of coatings spanning a broad wavelength range on a wide variety of materials. We produce coatings for a multitude of applications, ranging from environmental monitoring to space-based astronomy, Life Sciences, Spectroscopy, military and defense. Our AS9100 certification ensures compliance with aerospace and military standards, and ITAR.

Dichroic Filter Coatings

Andover designs and produces custom dichroic filter coatings for a variety of applications. Our in-house engineers can design exotic coatings to meet very stringent spectral and environmental requirements. As with all of our coatings, they can be applied to a wide variety of materials, in a myriad of shapes and sizes.

Heat Control Coatings

A hot mirror is a dichroic filter that reflects 90% of near-infrared (NIR) and infrared (IR) light while transmitting up to 90% of the visible light. Hot mirrors transmit shorter wavelengths and reflect infrared energy. Hot mirrors can be specified for an angle of incidence ranging from aero to 45 degrees AOI.

A cold mirror is a dichroic filter that reflects up to 90% of the visible light spectrum while allowing transmission of infrared wavelengths IR and near IR of up to 90%. Cold mirrors reflect the shorter wavelengths and transmit the heat (infrared). A cold mirror can be specified for an angle of incidence ranging from zero to 45 degrees.

Anti-Reflective AR Coatings

Andover produces hard oxide AR coatings from 193nm to 14μm. We routinely coat customer-supplied substrate material in all shapes and sizes: Flat optics, fibers, lenses, prisms, domes, etc. We can coat a wide variety of materials, ranging from typical optical glass to exotic materials such as Calcium Fluoride, Zinc Sulfide, and Zinc Selenide. The hard coatings not only reduce reflections to <0.1% at angles up to 50°, but also help protect optical surfaces, as the coating is more durable than the uncoated substrate. 

*HIGH VOLUME* - This product lends itself to being produced in large quantities at competitive pricing. Email or fill out a contact form for details.

Neutral Density Filters

Andover is a leader in flat response neutral density filters in the UV to near-infrared (250nm-2000nm) and far-infrared (2000-14000nm). These coatings are hard and pinhole-free. Our ND Filters exhibit industry-leading spectral neutrality over a broad wavelength range, with optical densities up to 4.0. Andover's absorptive ND filters are unique in that they are AR coated to reduce surface reflections. This enables them to be stacked without concern about losses and unwanted artifacts due to multiple reflections.

*HIGH VOLUME* - This product lends itself to being produced in large quantities at competitive pricing. Email or fill out a contact form for details.

Bandpass Filters

We produce bandpass filters over a much broader range than any other coating firm, from 193nm to 14μm in wavelength. Bandwidths range from very wide, (> 10%) to extremely narrow, (< 0.02%). We can produce semi-custom bandpass filters with short lead times. We also have over 1,500 standard filters.

Specialized Coatings

With our computer-controlled systems, we can quickly produce a variety of high-quality coatings in sizes up to 300mm with excellent repeatability using any process from resistance evaporation to magnetron sputtering. We also offer Ion-assisted e-beam deposition and Hybrid technologies.

Specifications depend considerably on the light wavelength range. Different kind of glasses and coatings can improve performance in particular spectral regions.

Contact a technical sales representative for more information.



ISO 9001 and AS 9100 Certified. ITAR Registered.