By TelAztec LLC
A nano-texture is a collection of cone-like features that are fabricated into the surface of an optic like a lens or prism. An individual feature has height and width dimensions that are in the tens to a few hundred billionths of a meter, the nano-meter (nm) scale. These features are packed so tightly that their spacing is everywhere no more than 150-250nm. RAR is a sub-wavelength nano-texture that creates a “graded-index surface”, gradually transitioning from air to the bulk material. Unlike conventional thin-film AR coatings, which rely on interference between multiple layers, RAR controls the effective refractive index through the density and depth of the nano-texture — providing broadband, low-reflection performance without thin-film coatings. TelAztec’s Random Anti-Reflection, or RAR nano-texturing process creates such randomly distributed features that provide extreme AR function over a huge range of wavelengths, all while avoiding losses from scatter or diffraction. The graded refractive index function produced by nano-texturing reduces reflections to levels typically below 0.1% over a huge range of wavelengths. For laser applications, the reflection loss can be driven 10 times lower to the 0.01% level over a specific band such as the 266-365nm UV laser range, or the 1030-1080nm near infrared wavelength range of industrial laser optics, or the 1500-1600nm telecommunications optics wavelength band. This allows the RAR solution to be tailored to the wavelength and performance requirements of the application. RAR adds no absorption because it contains no thin-film coating layers that can introduce absorption. The structures that make up the RAR nano-texture are created by removing material from a polished surface using a proprietary and patented dry plasma etch process. This fast and efficient subtractive manufacturing method results in the texture inheriting all of the optical, mechanical, and chemical durability of the bulk optic material. This is especially important for high-power laser optics; eliminating coating absorption minimizes heating and thermal lensing, helping maintain optical performance and enabling significantly higher laser-damage thresholds. So for RAR nano-textured lenses, windows, and fiber end caps made from low absorption fused silica glass, we say that there is “Zero-Added Surface Absorption” from the nano-texture. RAR maintains its graded-index performance at steep angles of incidence, delivering exceptionally low reflectance, even out to 60°. This provides unprecedented off-axis optical performance compared with conventional AR coatings. When light crosses an RAR nano-textured interface at higher angles, the graded refractive index appears the same but the texture depth appears to be reduced. This means that the ultra-low loss of RAR will be maintained, but the huge performance bandwidth will be reduced slightly for light incident at 30°, 45° or higher. The nanoscale surface structures reduce reflection by allowing light to transition smoothly between air and the optical surface. While all surfaces with nano-features may introduce some degree of scatter, the design of RAR nano-textured optics specifically targets a balance between reducing reflection and maintaining minimal scatter. While looking at the spectral performance graphs, many choose the RAR-VL variant for its low surface reflection, when a different variant may perform better for your application. Please contact our support team for help finding the best solution for you. The RAR nano-texture solution can be effectively implemented on curved surfaces and is designed to maintain its anti-reflective and scatter-reducing properties regardless of surface curvature. Advanced fabrication techniques enable the nano-scale surface structures to be uniformly patterned across both flat and complex geometries. The RAR nano-texture solution is highly versatile and effective for a wide range of optical materials, including diamond, sapphire, and IR materials. Nano-texturing these materials minimizes reflections while preserving their exceptional optical properties. RAR nano-textured optics are not fragile and are easy to clean. However, conventional cleaning techniques used for thin-film coatings — such as the drop-and-drag method or physical wiping — should be avoided.
