Unveiling the effects of the surface and in-depth nanostructure on the far-UV optical reflectance of thin fluoride multilayer coatings

López-Reyes, P.; Enríquez, E.; Crespillo, M.L.; Rodríguez-De Marcos, L.V.; Olivares, J.; Larruquert, J.I.

doi:10.1016/j.apsusc.2023.158455

Cited by 3 publications

(1 citation statement)

References 40 publications

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“…Two of the main challenges of metal fluoride-based MLs are that they grow with non-negligible tensile stress of thermal origin and the increasing roughness with the number of layers [ 7,9 ]. The first one is caused when deposited on a heated substrate to increase the metal fluoride density [ 10 ], especially when low-expansion substrates are used since fluorides have a relatively large thermal expansion coefficient.…”

Section: Comparison Between Alf3/laf3 and Mgf2/laf3 Mlsmentioning

confidence: 99%

Narrowband mirrors based on fluorides tuned at vacuum ultraviolet wavelengths

López-Reyes,

Honrado-Benítez,

Gutiérrez-Luna

et al. 2024

Advances in Optical Thin Films VIII

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The interest of the astrophysics community to make space observations in the vacuum ultraviolet (VUV, triggers the research to overcome the challenges to develop efficient VUV optics due to material absorption and the limited knowledge of optical constants. Future space observatories like the "Habitable Worlds Observatory, HWO/NASA" require efficient coatings capable of providing high-throughput image bandpasses in the VUV which is currently included as a NASA technology gap. Among the scarce transparent materials in this range, some metal fluoride materials exhibit the shortest cutoffs. Typically, highreflective narrowband coatings consist of periodic combinations of fluoride multilayers (MLs), with relatively high contrasting refractive index, such as MgF2/LaF3 or AlF3/LaF3 MLs.In this context, GOLD-IO-CSIC group has been developing high-performance all-dielectric VUV coatings, with special emphasis on short wavelengths down to 120 nm. This short VUV range is relatively unexplored and shows a comparatively lower performance due to the increased absorption of fluorides towards shorter wavelengths. Here, we present coatings based on combinations of MgF2/LaF3 and AlF3/LaF3 MLs, which can be tuned at any VUV wavelength >120 nm with a remarkable performance above 85% at H Ly-α (121.6 nm) for AlF3/LaF3 MLs; this improves the state-of-the-art at such short wavelengths. We also present a comparative study on the nanostructural morphologies of the two sets of MLs.Both the selection of the ML materials and the introduction of some aperiodicity on the ML designs allow choosing the bandwidth or the desired optical profile with remarkable freedom.Below ~120 nm there is no suitable combination of fluorides since all fluorides but LiF turn absorbing. We, then, present narrowband coatings based on Al, LiF, and SiC films, tuned at ~100 nm, with a strong rejection at the close H Ly-α line that could mask the observations.

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Section: Comparison Between Alf3/laf3 and Mgf2/laf3 Mlsmentioning

confidence: 99%

Narrowband mirrors based on fluorides tuned at vacuum ultraviolet wavelengths

López-Reyes,

Honrado-Benítez,

Gutiérrez-Luna

et al. 2024

Advances in Optical Thin Films VIII

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Examining the influence of W thickness on the Si-on-W Interface: A comparative metrology analysis

Valpreda,

Sturm,

Yakshin

et al. 2024

Applied Surface Science

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High performance La_1-xAl_xF₃ nanocomposite coatings prepared by a co-evaporation technique

Jiao,

Li,

Niu

et al. 2024

Opt. Express

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La1-xAlxF3 nanocomposite coatings with various amounts of AlF3 in LaF3 were deposited on the fused silica substrate using double-source electron beam co-evaporation. The effects of the material composition on the chemical composition, optical properties, microstructure properties, and residual stress of these deposited coatings were investigated. The results showed that although the doping of AlF3 led to a reduction in the refractive index, the overall performance of the nanocomposites showed remarkable improvement. The increase in the AlF3 content of prepared nanocomposites caused a decrease in the crystallinity, surface roughness, residual stress, and optical loss. Compared to polycrystalline LaF3, the La1-xAlxF3 nanocomposite (x ≥ 0.3) retained an amorphous structure, showcasing smooth surface morphology and lower absorption. As a result, the total optical loss was reduced. Additionally, the tensile stress was also mitigated to a certain extent, which means that the nanocomposite material was less prone to cracking. Finally, a 193 nm-La0.70Al0.30F3/AlF3 high reflective coating was prepared, which achieved an improved reflectance of 98.7% and better film quality compared to the pure LaF3/AlF3 sample. These findings clearly indicate the significant potential of La1-xAlxF3 nanocomposites for developing deep ultraviolet band thin films, extending even into the vacuum ultraviolet band.

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Unveiling the effects of the surface and in-depth nanostructure on the far-UV optical reflectance of thin fluoride multilayer coatings

Cited by 3 publications

References 40 publications

Narrowband mirrors based on fluorides tuned at vacuum ultraviolet wavelengths

Narrowband mirrors based on fluorides tuned at vacuum ultraviolet wavelengths

Examining the influence of W thickness on the Si-on-W Interface: A comparative metrology analysis

High performance La_1-xAl_xF₃ nanocomposite coatings prepared by a co-evaporation technique

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Unveiling the effects of the surface and in-depth nanostructure on the far-UV optical reflectance of thin fluoride multilayer coatings

Cited by 3 publications

References 40 publications

Narrowband mirrors based on fluorides tuned at vacuum ultraviolet wavelengths

Narrowband mirrors based on fluorides tuned at vacuum ultraviolet wavelengths

Examining the influence of W thickness on the Si-on-W Interface: A comparative metrology analysis

High performance La1-xAlxF3 nanocomposite coatings prepared by a co-evaporation technique

Contact Info

Product

Resources

About

High performance La_1-xAl_xF₃ nanocomposite coatings prepared by a co-evaporation technique