Developing a Durable MWIR/LWIR AR Coating for Chalcogenide
The challenge was to develop MWIR/LWIR AR coatings for several different IRG chalcogenide lenses that met spectral requirements as well as multiple environmental and durability tests. This required high transmission values over the several bandwidths in the 3-14µm range and all lenses had to meet this both pre- and post-environmental testing. Due to the material composition, it is difficult to achieve good adhesion and pass environmental testing.
This new request came to us after having multiple coating durability failures and delivery problems from several other coating vendors using this material. This also resulted in missed delivery dates to the end customer. The project required several different lens types.
We had already developed durable coatings for the same IR wavelengths applied to germanium substrates. The next step was to redesign these coatings for the chalcogenide material; it required different coating materials and process temperatures because of the specific limitations of this type of material. After extensive coating process development and rigorous environmental testing, we were able to successfully coat and meet the customer’s requirements.
The customer performed all environmental and durability testing to confirm the results and certified it to the end customer. We then coated all the remaining lens types and enabled our customer to deliver the parts to their customer.
Accucoat can provide coatings for the entire range of IR coatings on chalcogenide and other typical IR substrate materials.
Rehabbing Original FTIR Mirrors
A customer with multiple sets of damaged gold plated industrial FTIR mirrors wanted to experiment with the possibility of saving the mirrors, some dating back to 2008, versus replacing them with new ones. The mirrors sent to us had degradation to the gold plating from a harsh use environment, and we first needed to verify that we could repair it. We could not tell when the mirrors arrived if the nickel plating under the gold was damaged or not. By stripping the damaged gold off and recoating the surface with our PVD gold, we returned the mirrors to a fully functional state. This process saved multiple sets of very expensive mirrors and prevented the customer from having to replace them, allowing a significant cost saving.
Coating Aluminum Optic Spinners for an NIR Application
This diamond-turned aluminum optic with a NIR coating project required a very high reflectivity with stringent specifications for environmental testing and durability factors. The challenge was to coat the multiple facets of each part uniformly. To successfully perform this, we needed to include custom fabricated spacers to allow the stacking of the components on rotating spindles to stabilize parts as they orbit the coating chamber. Our approach allowed for the uniform deposition of the coating on all of the facets while protecting any perpendicular surfaces from overspray. In order to enhance the NIR performance and stability over the life of the product, we added a dielectric protection layer to the gold metal layer.
Our attention to detail allowed for very high yield as well as high run-to-run consistency for delivered, measured performance: a reflectivity > 98% @1550nm across wide-angle (AR) was consistently achieved. We have applied a similar, proven process to other polygon spinners and cylinders that require anti-reflective coatings for near-IR applications. Our HEPA filtered booths adjacent to the coating chamber assist in keeping pre-cleaned parts in “coating ready” condition.
For coating optics for LiDAR, barcode scanners, laser guidance systems, or other multi-directional scanners in high volumes, we are here to help your project go smoothly.
Local Touch, Global Reach
Although located in the optics hub of Rochester NY, AccuCoat has supported companies working globally with solving custom thin-film coating questions. Our exceptional attention to detail throughout the entire process from design to verification to repacking is monitored and scheduled. The team works proactively to avoid issues and as a result, we can typically offer higher yields, resulting in lower costs. The perils of shipping glass and other fine optics are mainly avoided when using our custom tooling kits to provide stable environments during heavy movement. For these reasons, combined with our on-time delivery commitment, customers outside of the US work with us consistently for their custom thin-film coating needs.
"For more than 10 years AccuCoat Inc. has provided coating services for us. When we originally introduced our first light source using plastic optics, we were looking for a provider of AR coating (broad band) on polymers. AccuCoat Inc. was identified as one company of only a few that provide this service. Since the beginning we have been very pleased with the quality of the coatings from AccuCoat Inc. Within all these years, they have guided us towards solutions that could improve either our quality, yield or make the process more efficient for us.
We have always found AccuCoat Inc. very easy to communicate with, that is today a very important quality in the global community."
Delivering More Value with Increased Yield, Part Performance and Durability
Our customer came to us with several AR coating issues on Germanium. They were struggling with marginal coatings that sometimes failed performance testing for transmission at 4.4 um. The coatings were not consistently durable for the intended environment, which was a problem for the end-user.
To address these critical issues, we started by developing a new coating design to alleviate the transmission problem and created a plasma cleaning step that allowed the parts to meet the demanding eraser durability test parameters. These actions resulted in the parts exceeding the transmission performance required for the application.
Our customer was very pleased with the redesigned part performance and the fact that they could now satisfy their customers by delivering a higher transmission rate.
In addition to developing a solution that performed over and above for both performance and durability, we also increased the volume of parts delivered, which the previous supplier was unable to match.
As a result of our much higher yield rates, the improved AccuCoat parts were created at a similar cost to the customer, with a measurably improved acceptance rate over the past provider.
For more information on our AR coating options, read more...
Coating Beam Splitters for the Film Industry
The film industry always pushes the envelope for creativity, which creates new opportunities in the coating realm. By using a beam splitter part in a special holder in front of the camera lens, colored special effects can be created during action sequences as shot. AccuCoat offers fully custom thin-film coatings on beam splitters with ratios from 90R/10T to 10R/90T and anything in between, creating that unique look. Polarization is typically offered in an immersed option from 50-100 nm wavelengths if required. If a hybrid, non-polarized option is needed, a dielectric coating on large glass or polymer plates can be created at 50R/50T or 70R/30T to be held at an angle for light reflection.
Read our tech note on "Beam splitters: Divide, combine & conquer"
Coating Freeform Optics
Polymer optics, created by injection molding or diamond-turned into a freeform or aspheric optic design, are regularly coated by AccuCoat. Because of the level of difficulty to manufacture correctly, we have developed a specific process for precise and predictable coatings for freeform prisms with multiple aspheric surfaces or other shapes that are commonly too difficult to conventionally fabricate with glass. This type of optic is typically constructed from materials such as Zeonex, acrylic, polystyrene or Ultem.
AccuCoat has 20 years of experience with developing specific custom tooling that allows correct and complete coverage to these non-flat surfaces. Onsite, we have a fully-automated ultrasonic process for perfectly cleaned high-value SPDT coated optics.
Optical coatings applied to freeform or diamond-turned products are typically used in head-mounted displays providing in-the-moment data or VR imaging used for military and high-end commercial projects.
Read our Tech Note for more detail regarding how we coat SPDT optics …
Coating micro-optics requires an elegant combination of tooling, orientation, and rotation within the coating chamber to apply a uniform film that conforms to every nook and cranny without filling in the low points. We can coat plastic or glass micro-optics with any of our standard coating types – from lenslet arrays, Fresnel structures, and diffusers to highly angled diffractive structures such as ruled gratings. By using relatively thin coatings (<0.5 µm) and the right fixtures and coating processes, we improve spectral performance without negatively impacting beam propagation. We can even apply different coatings on different facets, carefully designing the tooling to mask the appropriate area at each stage for precision application of AR, high reflector, or beamsplitter coatings to each location. No challenge is too small!
Spinners & Polygons
Optical coatings applied to spinners are used in critical laser guidance systems, bar code readers, land surveying, and LIDAR technology. At AccuCoat, we coat these multifaceted polygons and cylinders using a sophisticated system that enables rotation of parts around multiple axes simultaneously. This ensures we can deliver uniform high reflectivity and AR coatings, whether on injection molded plastic parts or high precision spinners for premium laser market applications.
Read our tech note on coatings used in LiDAR applications.
The OEM that came to us had been using a small triangular coated glass window at the end of a gunsight, but was seeing frequent cracking in the field due to the rough handling. They needed a drop-in replacement window in plastic that met both the needed optical performance and all environmental requirements (including chemical exposure and severe temperature cycling). Of the three suppliers who provided prototype optics in plastic, AccuCoat was the only one to pass the full suite of environmental tests.
Read our tech note on how we meet the demanding needs of the defense industry.
Hot Mirrors for Virtual Reality
Hot mirrors are used in virtual reality (VR) systems to reflect the IR light used by eye or positional tracking systems while passing the visible light. These heads-up display optics need to be lightweight, and thus are coated on plastic. Optical requirements for VR vary, but can include 80-90% reflection of 800-830 nm light or nonpolarizing beamsplitting of the laser and visible, both of which are possible using AccuCoat coatings on plastic substrates.
AR Coated Mylar Sheets
The laser instrumentation and diagnostics markets have a need for very thin (2 mil) mylar coated sheets. By adjusting coating processes and developing custom tooling to accommodate the thin, flexible material, current coating technology can achieve a uniform AR V-coat across the sheet without compromising pliability; the coated sheet can even be rolled up and flexed without cracking or crazing the coating.
Read our tech note on how we apply durable coatings to plastic and polymer substrates.