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arXiv · 2606.18813

Magnetic-polarization-dependent spectroscopy of lanthanide-doped anisotropic crystals

Zoe Liestmann·Luca Koldeweyh·Moritz Badtke·Sascha Kalusniak·Christian Kränkel·Hiroki Tanaka
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Abstract

We experimentally demonstrate that absorption and emission spectra of trivalent lanthanide-doped anisotropic crystals can exhibit a significant magnetic-polarization dependence, which has been largely overlooked in spectroscopic studies to date. Focusing on the uniaxial laser host LiYF4 (YLF) doped with Yb3+, Tm3+, Er3+, and Ho3+, we measure magnetic-polarization-dependent absorption and emission spectra for transitions with strong magnetic-dipole (MD) contributions predicted by theory. Our results reveal that MD-induced spectral anisotropy, i.e., spectral differences for the same electric field orientation but for different magnetic field orientations, is present even in these well-established laser materials. A complete spectroscopic characterization of uniaxial crystals requires three polarizations, including the $\alpha$-polarization, with both the electric field vector E and the magnetic field vector H perpendicular to the c-axis (E $\perp$ c, H $\perp$ c), in addition to the commonly used two polarizations $\pi$ (E $\parallel$ c, H $\perp$ c) and $\sigma$ (E $\perp$ c, H $\parallel$ c). We further discuss the observed MD-induced spectral anisotropy and calculated MD branching ratios, the impact of the anisotropy on emission cross-section calculations, and the relevance of our results to other uniaxial and biaxial crystals.

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Zoe Liestmann, Luca Koldeweyh, Moritz Badtke, Sascha Kalusniak, Christian Kränkel, Hiroki Tanaka. 2026-06-17. Magnetic-polarization-dependent spectroscopy of lanthanide-doped anisotropic crystals. https://arxiv.org/abs/2606.18813

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