arXiv subjects

Dmitriy Grudinin

Publications and source records attributed to Dmitriy Grudinin.

5 recordsLinked to original sources

arXiv2025

Scalable van der Waals Photonics: High-Refractive-Index Gallium Sulfide Films with Single-Crystal Optical Properties

The integration of high-refractive-index dielectrics into scalable photonic architectures is foundational to advancing integrated circuits and augmented reality (AR) displays. Van der Waals (vdW) materials offer exceptional optical properties, including high refractive indices and giant anisotropy, but their implementation is constrained by the small area and uncontrolled thickness of mechanically exfoliated flakes. Here, we demonstrate that atomic layer deposition (ALD) grown gallium sulfide (GaS) overcomes the trade-off between high optical performance and manufacturability, emerging as a large-scale vdW dielectric platform. Through rigorous optical and structural benchmarking against pristine single crystals, we establish that the optical constants (n, k) of ALD-GaS are virtually indistinguishable from single-crystal counterparts. By leveraging the retained out-of-plane anisotropy, we demonstrate that ALD-GaS enables superior suppression of crosstalk in densely integrated waveguides compared to conventional scalable high-index platforms. Our findings establish ALD-GaS as a technologically viable pathway for implementing anisotropic vdW materials in visible-spectrum photonics.

physics.optics↗

arXiv2025

Giant optical anisotropy and visible-frequency epsilon-near-zero in hyperbolic van der Waals MoOCl2

The realization of extreme optical anisotropy is foundational to nanoscale light manipulation. Van der Waals (vdW) crystal MoOCl2 has emerged as a promising candidate for this quest, hosting hyperbolic plasmon polaritons in the visible and near-infrared wavelengths. However, the fundamental anisotropic dielectric tensor governing this behavior has remained elusive. Here, we resolve this problem by providing the first experimental determination of the full dielectric tensor of hyperbolic vdW MoOCl2. Via spectroscopic ellipsometry, Mueller matrix, and reflectance measurements, we quantify the material's optical duality: a metallic optical response ({\epsilon}_1 < 0) along the crystallographic a-axis and a dielectric response ({\epsilon}_1 > 0) along the orthogonal directions. This dichotomy drives an epsilon-near-zero (ENZ) condition at \approx 512 nm and results in giant in-plane birefringence of \delta n \approx 2.2 for MoOCl2. As a result, our work provides the critical missing experimental parameters for MoOCl2, establishing it as a benchmark hyperbolic and ENZ material.

physics.optics↗

arXiv2025

Giant optical anisotropy in CrSBr from giant exciton oscillator strength

The interplay between dimensionality and electronic correlations in van der Waals (vdW) materials offers a powerful toolkit for engineering light-matter interactions at the nanoscale. Excitons, bound electron-hole pairs, are central to this endeavor, yet maximizing their oscillator strength, which dictates the interaction cross-section, remains a challenge. Conventional wisdom suggests a trade-off, where the observable oscillator strength often decreases in strongly bound systems due to population dynamics. Here, we unveil a colossal oscillator strength associated with the quasi-one-dimensional (quasi-1D) excitons in the layered magnetic semiconductor CrSBr, which fundamentally defies this established scaling law. Through comprehensive optical characterization and ab initio calculations, we establish that this anomalous enhancement originates directly from the reduced dimensionality, which enforces an increased electron-hole wavefunction overlap. Moreover, we find a close connection between fundamental exciton and local spin fluctuations that contribute to the opening of the gap in the electronic spectrum. The resulting optical anisotropy shows a giant in-plane birefringence (Delta_n = 1.45) and profoundly anisotropic waveguiding, which we directly visualize using nano-optical imaging. Leveraging this extreme response, we realize a true zero-order quarter-wave plate with an unprecedented wavelength-to-thickness ratio (lambda/t) exceeding 3.4, surpassing the limits of current miniaturization technologies, including state-of-the-art metasurfaces. Our findings underscore the profound impact of dimensionality engineering in magnetic vdW materials for realizing novel regimes of light-matter coupling and developing next-generation ultracompact photonic architectures.

cond-mat.mtrl-sci↗

arXiv2025

Giant exciton binding energy in bulk CrCl3

Van der Waals (vdW) materials, with their unique combination of electronic, optical, and magnetic properties, are emerging as promising platforms for exploring excitonic phenomena. Thus far, the choice of materials with exceptional excitonic response has been limited to two-dimensional (2D) configurations of vdW materials. At the same time, large interlayer distance and the possibility to create a variety of heterostructures offers an opportunity to control the dielectric screening in van der Waals heterostructures and van der Waals 3D materials, thus engineering the excitonic properties. Here, we reveal that bulk vdW crystal CrCl3 answers this quest with a record exciton binding energy of 1.64 eV owing to a delicate interplay of quasi-2D electronic confinement and local magnetic correlations. We also suggest that the non-local magnetic correlations play an important role in the temperature dependence of photoluminescence intensity. Furthermore, we observe colossal binding energies in vdW crystals NbOCl2 (0.66 eV) and MoCl3 (0.35 eV) and formulate a universal exciton binding energy dependence on bandgap for 2D and 3D vdW materials. Hence, our findings establish a fundamental link between the layered structure of vdW materials and their excitonic properties.

cond-mat.mtrl-sci↗

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↗