biostudies-literatureUnknown11(17)John JWe theoretically and experimentally demonstrate a strong and tunable optical anisotropy in epitaxially-grown VO₂ thin films. Using a combination of temperature-dependent X-ray diffraction, spectroscopic ellipsometry measurements and first-principle calculations, we reveal that these VO₂ thin films present an ultra-large birefringence (Δ<i>n</i> > 0.9). Furthermore, leveraging the insulator-to-metal transition of VO₂, we demonstrate a dynamic reconfiguration of optical properties from birefringent to hyperbolic, which are two distinctive regimes of anisotropy. Such a naturally birefringent and dynamically switchable platform paves the way for multi-functional devices exploiting tunable anisotropy and hyperbolic dispersion.Nanophotonics (Berlin, Germany)3913-3922https://www.ebi.ac.uk/biostudies/studies/S-EPMC11501475biostudies-literatureTunable optical anisotropy in epitaxial phase-change VO&lt;sub&gt;2&lt;/sub&gt; thin films.PMC11501475Slassi ACueff SRamanathan SOrobtchouk RJohn JBachelet RCalzolari APenuelas JSun YSun JSaint-Girons GfalseTunable optical anisotropy in epitaxial phase-change VO&lt;sub&gt;2&lt;/sub&gt; thin films.We theoretically and experimentally demonstrate a strong and tunable optical anisotropy in epitaxially-grown VO₂ thin films. Using a combination of temperature-dependent X-ray diffraction, spectroscopic ellipsometry measurements and first-principle calculations, we reveal that these VO₂ thin films present an ultra-large birefringence (Δ<i>n</i> > 0.9). Furthermore, leveraging the insulator-to-metal transition of VO₂, we demonstrate a dynamic reconfiguration of optical properties from birefringent to hyperbolic, which are two distinctive regimes of anisotropy. Such a naturally birefringent and dynamically switchable platform paves the way for multi-functional devices exploiting tunable anisotropy and hyperbolic dispersion.2022-01-01T00:00:00Z2022 Sep2025-04-04T00:46:18.29Z2025-04-04T00:46:18.29ZS-EPMC115014753963516810.1515/nanoph-2022-0153