Epsilon near zero (ENZ) materials have potential in various applications such as all-optical switching and quantum information. Materials that support ENZ modes include metamaterials, semiconductors, and transparent conducting oxides (TCOs) like indium tin oxide (ITO). ITO supports an ENZ mode in the near-infrared (IR), giving rise to large nonlinearities and enabling strong optically induced changes in its refractive index. Recently, a perovskite TCO, La-doped BaSnO3 (LBSO) has demonstrated wide tunability of the ENZ wavelength ranging from the near IR to mid-IR regions. In this work, we use a reflective gold layer to access the Ferrell-Berreman (FB) mode of LBSO, a special class of leaky optical mode that occurs at the material’s ENZ wavelength. The FB mode has strong extinction, making it an ideal candidate for reflection modulation. Here, we interrogate the charge carrier dynamics of multiple Au-coated LBSO samples with varying ENZ wavelengths, paying special attention to the tuning behavior of the FB mode. We find that, upon UV excitation, injected charge carriers are long-lived compared to other transparent conducting oxides and that the photoexcited carriers induce strong modulation of the FB mode. This Au-coated LBSO shows promise for infrared optical switching applications, especially those requiring high thermal stability.
Gebre et al. (Tue,) studied this question.