arXiv subjects

Ilia Fradkin

Publications and source records attributed to Ilia Fradkin.

2 recordsLinked to original sources

arXiv2025

Hyperbolic-enhanced Raman scattering in van der Waals MoOCl2: from Fano resonances to picomolar detection

Natural van der Waals (vdW) crystals with hyperbolic dispersion challenge artificial metamaterials but remain confined to the mid-infrared. The emergence of MoOCl2, a quasi-one-dimensional metal with in-plane hyperbolicity, overcomes this spectral limit, shifting the focus to the practical visible range. Here, using angle-resolved polarized Raman spectroscopy, we uncover pronounced polarization-dependent Fano lineshapes that reveal coupling between phonons and the anisotropic metallic continuum, together with strong wavelength-dependent reshaping of the Raman polarization patterns governed by the anisotropic optical response of MoOCl2. Harnessing this optical anisotropy, we demonstrate "Hyperbolic-Enhanced Raman" (HypER) scattering, where MoOCl2 provides polarization-tunable analytical enhancement factors exceeding 10^7 and picomolar-level detection of Rhodamine 6G down to 100 pM, without deliberate surface nanostructuring. These results establish air-stable MoOCl2 as a simple, wafer-compatible platform for visible-range hyperbolic nanophotonics and lithography-free sensing.

physics.optics↗

arXiv2024

Anisotropic van der Waals Crystal with High Refractive Index and Transparency for UV-Visible Range Applications

Thanks to their record high refractive index and giant optical anisotropy, van der Waals (vdW) materials have accelerated the development of nanophotonics. However, traditional high refractive index materials, such as titanium dioxide (TiO2), still dominate in the most important visible range. This is due to the current lack of transparent vdW materials across the entire visible spectrum. In this context, we propose that germanium disulfide (GeS2) could offer a significant breakthrough. With its high refractive index, negligible losses, and biaxial optical anisotropy across the whole visible range, GeS2 has the potential to complement TiO2 and close the application gap of vdW materials in the visible spectrum. The addition of GeS2 could have a profound impact on the design of van der Waals nanophotonic circuits for any operation wavelength from ultraviolet to infrared, emphasizing the significance of the potential impact of GeS2 on the field of nanophotonics.

physics.optics↗