Microscale structures on the surface of optical interfaces have been known for over a century as an effective method of reducing Fresnel reflections. The eyes of a moth are covered with a natural anti-reflective nanostructured film.
The moth-eye pattern is a pattern of subwavelength “bumps”; reduces reflection by creating an effective refractive index gradient between the air and the medium.
The moth-eye structure is one of the most effective nanostructures to reduce reflection
Moth-eye nanostructures can be patterned on surfaces to give them antireflection properties
Moth-eye structures have several advantages over traditional thin-film AR coatings
Minimal surface preparation
Higher laser-induced damage threshold
Self cleaning (lotus effect)
Moth-eye structures are especially useful for reducing reflections from and increasing transmission between materials with a large refractive index contrast
Particularly important in high-power & low-loss applications
Moth-eye AR structures have found uses in a number of applications, including laser systems, photovoltaics, LEDs, electronic displays, and fiber optics
In this work, we optimize the shape and dimensions of moth-eye structures for maximum output coupling through the endfaces of 𝐴𝑠2𝑆3 (n=2.45) chalcogenide optical fibers.
Rigorous computational EM propagation methods, like FDTD and RCWA, can be used to accurately simulate the transmission/reflection from the moth-eye surface.
For this particular moth-eye structure, RSoft’s DiffractMOD RCWA tool is utilized due to RCWA’s speed advantages over FDTD
RSoft’s MOST Optimization and Scanning Utility is used in conjunction with DiffractMOD to optimize the reflection/transmission for the moth-eye AR pattern