Determination of the refractive index of BaY<inf>2</inf>F<inf>8</inf>:Er<sup>3+</sup> (0.5 mol% to 30 mol%) in the 300 nm–1800 nm range by ellipsometry; a record-breaking upconversion material

Elsevier BV
Publication Type:
Journal Article
Journal of Luminescence, 2021, 230, pp. 117639-117639
Issue Date:
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© 2020 The Author(s) This work reports the ellipsometric study of trivalent erbium (Er3+) doped monocrystalline barium yttrium fluoride (BaY2F8), which has recently been shown to be one of the best photon upconversion (UC) materials available. This spans the BaY2F8 applications in a large range of wavelengths, from ultraviolet (UV) to near-infrared (NIR). We detail the optical properties of BaY2F8: Er3+ (0.5 mol%, 10 mol%, and 30 mol%), measured via variable angle spectroscopic ellipsometry over a spectral range from 300 nm to 1800 nm, reporting for the first time the indices of refraction for BaY2F8:Er3+. The upconversion external photoluminescence quantum yield (ePLQY) of the BaY2F8:Er3+ samples have also been studied by exciting at [JG]λ=1588nmλ=1493 nm. The highest ePLQY of BaY2F8 was found for the largest dopant concentration 30 mol% Er3+ reaching the value of [JG]1.07% ± 0.12%, at an irradiance of 9.512 ×10−2W/cm23.62% ± 0.01%, at an irradiance of (6.23 ± 0.45) ×10−2 W/cm2. The refractive index (λ= 589.3 nm) was determined to be 1.4808± 0.014 for 0.5 mol%, 1.4980± 0.003 for 10 mol%, and 1.5022± 0.006 for 30 mol%. Increasing Er3+ doping concentration increased the refractive index. All samples decreased monotonically with increasing wavelength. The Brewster angle of BaY2F8:Er3+ is observed to be ≈ 56∘, whilst the Abbe number of the samples was found to be as high as 124.62. These findings provide valuable insight into the optical properties of BaY2F8:Er3+ in the wide range of frequencies that is has proven useful.
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