Abstract
We computationally investigate moth-eye anti-reflective nanostructures imprinted on the endfaces of As2S3 chalcogenide optical fibers. With a goal of maximizing the transmission through the endfaces, we investigate the effect of changing the parameters of the structure, including the height, width, period, shape, and angle-of-incidence. Using these results, we design two different moth-eye structures that can theoretically achieve almost 99.9% average transmisison through an As2S3 surface.
Highlights
It has been known since the time of Lord Rayleigh that microscale structures on the surface of optical interfaces are effective at reducing Fresnel reflections [1]
Reducing Fresnel reflections from optical interfaces is important in mid-IR applications, where high power and low loss are needed
Because in the structures studied in this work, the microstructure feature dimensions are on the same order as the wavelength of the incoming radiation (∼1 μm), light in adjacent features interacts, and neither the long-wavelength average refractive index model nor the short-wavelength ray optics model is appropriate to describe transmission through moth-eye structures
Summary
It has been known since the time of Lord Rayleigh that microscale structures on the surface of optical interfaces are effective at reducing Fresnel reflections [1]. Because in the structures studied in this work, the microstructure feature dimensions are on the same order as the wavelength of the incoming radiation (∼1 μm), light in adjacent features interacts, and neither the long-wavelength average refractive index model nor the short-wavelength ray optics model is appropriate to describe transmission through moth-eye structures They must be modeled using rigorous computational methods [16], such as the finite-element method (FEM), the finite-difference time-domain method (FDTD) [17, 18], or rigorous coupled-wave analysis (RCWA) [19, 20], where the results become exact in principle as the grid size and step size tend to zero (FEM and FDTD) or the number of harmonics becomes infinite (RCWA).
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