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Zero-contrast grating filters for pixelated applications in the mid-IR range

Abstract : Summary form only given. Pixelated filters are of great interest for spatial applications because they compare favourably with traditional filter-wheel multi-spectral imagers in terms of weight and footprint. The thin film technology, which is mainly used to produce filters in the mid-IR range is limited when it comes to fabricating pixelated designs, because the thickness of the stacks in two neighbouring pixels would be different, leading to intricate fabrication steps even though some original methods exist [1]. It has been shown recently that zero-contrast gratings (ZCG) can be used to implement bandpass transmission filters [2]. They consist of a partially-etched high-index material on a low-index substrate. The main advantage is that the central wavelength of the filter can be adjusted simply by modifying the lateral dimensions of the patterns, not the thickness of the high-index layer. However these filters possess 2 major limitations. First, they have a low angular tolerance which limits the smallest possible pixel size. Secondly, their bandwidth is only of few nm which restricts too much the incident flux. Indeed, since the total incident flux is divided along both spectral and spatial dimensions in multi-or hyper-spectral imagers, there is only little flux into each channel.In this paper we report a simple and efficient method to design narrowband transmission filters as well as the first use of a doubly-corrugated grating in order to increase both the bandwidth and angular tolerance of a ZCG. The design method relies on both analytical and empirical relations with very little numerical optimization conducted using Rigorous Coupled Wave Analysis (RCWA).
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https://hal.laas.fr/hal-01942961
Contributor : Olivier Gauthier-Lafaye <>
Submitted on : Monday, December 3, 2018 - 3:17:53 PM
Last modification on : Friday, January 10, 2020 - 9:10:14 PM

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Léopold Macé, Olivier Gauthier-Lafaye, Antoine Monmayrant, Henri Camon, Benjamin Portier, et al.. Zero-contrast grating filters for pixelated applications in the mid-IR range. CLEO-Europe/EQEC, Jun 2017, munich, Germany. ⟨10.1109/CLEOE-EQEC.2017.8087179⟩. ⟨hal-01942961⟩

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