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NIR-Tuned AntiReflection Coatings

Maximize transmission and minimize reflections

AntiReflection Coatings Tuned for Near Infrared (NIR) Applications

Applied to your choice of CLAREX Optical Grade Cell-Cast Acrylic Sheets

Standard acrylic sheets without any AntiReflection 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. AntiReflection coating is the answer. By decreasing the %Reflection coming off of each surface (front and back), the Total %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 broad band antireflection 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 Antireflection 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 of course.

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 Antismudge (oleophobic) coating for an easy-clean surface
  • Low to high volume
  • Easily machined or laser cut

Examples

Standard AntiReflection coating for the Visible Range

First, it’s best to see why the standard AntiReflection (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 low %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 %Reflections continue to increase. This is not going to make your NIR sensor happy!

BroadNIR AntiReflection coating designed for the NIR Range

This is a similar idea as 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 very high visible %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 AntiReflection coating designed for 850nm and low visible reflections

For some NIR applications, the high visible reflection of the BroadNIR 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 higher %Reflection at other NIR points. This example here is used for an 850nm application. However, that NIR design point could be shifted as needed.

1545 AntiReflection 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 BroadNIR coating, so the factory was able to offer the custom-tuned design.

1063/1545 AntiReflection coating designed for 1063nm & 1545nm

In this case the customer had a sensor working at 1063nm and another at 1545nm. The standard BroadNIR 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.

Remember, these are examples. The factory can custom tune the AntiReflection curves for your application. Please give us a call or email to discuss your particular requirements.