Random nanostructured infrared window scatter analysis using the Harvey-Shack transfer function method

David A. Gonzalez; Karun Vijayraghavan; Menelaos K. Poutous

doi:10.1117/12.2648542

15 March 2023 Random nanostructured infrared window scatter analysis using the Harvey-Shack transfer function method

David A. Gonzalez, Karun Vijayraghavan, Menelaos K. Poutous

Proceedings Volume 12430, Quantum Sensing and Nano Electronics and Photonics XIX; 1243018 (2023) https://doi.org/10.1117/12.2648542
Event: SPIE OPTO, 2023, San Francisco, California, United States

Conference Poster

Abstract

Random-distribution antireflective metasurfaces suppress specular reflection by selectively scattering light into the forward axial direction. These surfaces have been shown to produce broadband, polarization independent transmission enhancement in the visible and IR wavelength bands. Rigorous full-wave solvers of light scatter from aperiodic surfaces can be computationally intensive, therefore alternative methods are desired to predict and analyze bi-directional surface scatter. Using a transfer function approach, an approximation of far-field light scatter can be modeled based on surface statistics. Random rough surfaces, which are generally globally isotropic and polarization insensitive, are well-modeled by Gaussian statistics, making them ideal candidates for a surface transfer function approach of surface scatter analysis. For this study, Si windows were processed to have statistically random nanofeatures which were optimized to enhance transmission throughput in the MWIR (3-5 μm). Optical performance of structured samples was verified using FTIR spectrophotometry. Bidirectional scattering distribution function of processed substrates was measured at selected angles of incidence using a 3.39-μm-wavelength polarized-laser scatterometer. Surface statistics were obtained via non-contact profilometric methods and used as input for calculation of surface feature diffractive effects by the Generalized Harvey-Shack scatter theory. Scatter distributions predicted using a Gaussian approximation of a random surface and structured surface metrology data were compared to the measured scatter data for assessment of the transfer function model validity within the bandlimit of interest.

Citation Download Citation

David A. Gonzalez, Karun Vijayraghavan, and Menelaos K. Poutous "Random nanostructured infrared window scatter analysis using the Harvey-Shack transfer function method", Proc. SPIE 12430, Quantum Sensing and Nano Electronics and Photonics XIX, 1243018 (15 March 2023); https://doi.org/10.1117/12.2648542

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