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NIR-Tuned Anti-Reflective Coatings

Maximize transmission and minimize reflections

Anti-Reflective Coatings Tuned for Near Infrared (NIR) Applications

Applied to your choice of CLAREX optical-grade cell-cast acrylic sheets.

Standard acrylic sheets without any anti-reflective coatings will typically have about 4% reflection from each surface, front and back, for a total of 8%. Certain applications require maximum transmission through the optical filters/windows, minimum reflections from the surfaces, or both. Anti-reflective coatings are the answer. By decreasing the percentage of reflection coming off of each surface (front and back), the total percentage transmission through the material increases. With AR coatings on both sides of the sheet, it is possible to get >99% Transmission at your desired NIR design point.

When working in the Visible range (380-700nm), the standard broadband anti-reflective coating (BBAR) will typically do the trick. However, these standard coatings designed for the visible range don’t work so well as you move outside the visible range. For instance, for applications in the Near Infrared (NIR) range (700-1100nm), we are able to supply NIR-tuned anti-reflective coatings. We have a few examples below of the different types available. These can be custom-tuned, so if you don’t see what you need, we might still be able to help you.

The specs for the standard AR-coated sheets would still apply, with the exception of the optical curves.

And note that you can choose different AR coatings for the front and rear surfaces.

Features

  • AR coating tuned for NIR applications
  • With AR coating on both sides, you can achieve >99% Transmission at your NIR design point
  • Several design types to choose from
  • Applied to your choice of CLAREX optical grade cast acrylic sheets
  • Can apply different AR coatings on the front and rear surfaces
  • Can include anti-smudge (oleophobic) coating for an easy-clean surface
  • Low to high volume
  • Easily machined or laser cut

NIR Coating Examples

Standard Anti-Reflective Coatings
for the Visible Range

First, it’s best to see why the standard anti-reflective (AR) coatings designed for the visible range (380-700nm) don’t work well in the NIR range. As you can see here, the standard visible AR coating has a low percentage reflection in the visible range (compared to about 4% reflection from an uncoated surface). But the performance tapers off as you move out from the 550nm design point. At 775nm the coating has as much reflection as uncoated acrylic (4%). And then above 775nm the percentage reflections continue to increase. This is not going to make your NIR sensor happy!

Broad NIR Anti-Reflective Coating
Designed for the NIR Range

This is a similar idea to the Standard Visible AR coating above, except in this case, it is centered around 850nm so that it works well across the NIR range (700-1100nm). To an NIR Sensor, this will look great, as if the filter isn’t even there. However, this coating design has a very high visible percentage reflection. To the human eye, the coated surface will look as if it has a partial mirror coating. That may or may not matter to your application. If it does, continue reading…

850/VIZ Anti-Reflective Coating
Designed for 850nm and Low Visible Reflections

For some NIR applications, the high visible reflection of the Broad NIR AR coatings will not work. Perhaps there are multiple sensors, visible and NIR, looking through the optical filter. Or maybe the high visible reflection is just not aesthetically acceptable for the application. In those cases, we can supply AR coatings that are tuned to work at a specific NIR design point, and also have reduced visible reflections. The catch is that it will have a higher percentage reflection at other NIR points. This example is used for an 850nm application. However, that NIR design point could be shifted as needed.

1545 Anti-Reflective Coating
Designed for 1545nm

Here’s an example of an AR coating designed for a customer who was working at 1545nm. That’s outside the range of the Broad NIR coating, so the factory was able to offer the custom-tuned design.

1063/1545 Anti-Reflective Coating
Designed for 1063nm & 1545nm

In this case the customer had a sensor working at 1063nm and another at 1545nm. The standard Broad NIR AR coating would not work because the 1545nm was outside the design range. The factory was able to offer this custom-tuned AR coating as a solution.

Need a different customization? We can customize the anti-reflection curves to suit your specific application.

Please give us a call or email to discuss your particular requirements.

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