arXiv subjects

Ondřej Červinka

Publications and source records attributed to Ondřej Červinka.

4 recordsLinked to original sources

arXiv2026

Additive and Subtractive Color Filters Based on Birefringent Dielectric Metasurfaces

Dielectric metasurfaces offer a path to high-efficiency optical components at the sub-wavelength scale. In this work, we utilize the wavelength-dependent birefringence of TiO2 nanopillars to create transmissive color filters with switchable spectral responses. We demonstrate that the same physical nanostructure array can function as either an additive (band-pass) or a subtractive (band-stop) filter solely by rotating an external polarizer. The metasurface was fabricated via a modified damascene process, enabling high-aspect-ratio structures with spatial resolutions down to 250 nm. The filters achieve transmission efficiencies of 70% tailorable across the entire visible spectrum, avoiding the ohmic losses typical of plasmonic alternatives. This approach provides a tunable, high-efficiency platform offering a versatile and compact solution for next-generation high-resolution imaging systems.

physics.optics↗

arXiv2026

Durable Enhancement of $\mathbf{MoS_2}$ Single-Layer Photoluminescence by Ultraviolet Laser Treatment Under Ambient Conditions

Single-layer molybdenum disulfide ($MoS_2$) possesses significant potential for nanoscale optoelectronics, but achieving high-intensity, long-term-stable photoluminescence (PL) emission remains a challenge. In this work, we demonstrate a remarkably robust, more than 8-fold maximum enhancement in the PL intensity of exfoliated and CVD-grown single-layer $MoS_2$ via a non-destructive ultraviolet (UV) laser treatment method. This substantial increase in radiative efficiency is accompanied by a trion-to-neutral exciton transition in the PL signal and a corresponding blue shift of the Raman $E_{2g}^1$ and $A_{1g}$ vibrational modes, signaling successful electron depletion (p-doping) and formation of Mo-O bonds, respectively. Furthermore, we demonstrate precise spatial control over PL properties by confining PL treatment exclusively to the UV laser-treated area. Crucially, the enhanced PL performance shows exceptional longevity; the CVD sample and the exfoliated sample remained stable for the entire monitoring period (72 and 32 days, respectively) under ambient conditions. We further investigated UV laser treatment in a controlled-environment chamber under argon, nitrogen, and oxygen atmospheres, distinguishing the influence of oxygen as the PL treatment agent. These findings establish a reliable pathway for the permanent treatment of single-layer $MoS_2$ PL properties, an essential step toward practical, high-performance nanophotonic devices.

cond-mat.mes-hall↗

arXiv2026

Inverse designed full-Stokes polarimetric metasurface with simultaneous wavefront sensing for visible light

Metasurfaces have emerged as a powerful platform for compact optical sensors by replacing bulky lenses with flat arrays of subwavelength nanostructures. In precision optical metrology, the simultaneous mapping of a beam's polarization state and wavefront is crucial for real-time diagnostics of stress-induced birefringence and surface flatness. To achieve this in a compact footprint, existing metasurfaces typically partition their aperture into discrete zones, which inherently restricts the light-gathering efficiency and numerical aperture of the system. Here we demonstrate an inverse-designed metasurface that integrates full-Stokes polarimetry and Shack-Hartmann wavefront sensing within a single, continuous aperture in the visible spectrum. By leveraging an adjoint optimization approach to independently control the geometry and rotation of each nanostructure, we break the aperture-sharing paradigm and utilize the entire pixel area for all channels. When coupled with a shallow neural network to automate peak identification and correct for hardware non-idealities, our device yields a mean polarization reconstruction error of only 0.046 across 100 test states on the Poincaré sphere, while simultaneously maintaining the precise focal-spot tracking required for sensitive wavefront tilt detection. This work highlights the capacity of inverse design to generate multifunctional, non-intuitive flat optics that outperforms its traditional counterparts.

physics.optics↗

arXiv2025

Establishing a library of metasurface building blocks through coherence-controlled holographic microscopy

Digital holographic microscopy is a powerful tool for characterizing transparent and reflective phase objects. Its ability to reconstruct amplitude and phase can also offer great insight into wavefront shaping and design of all-dielectric optical metasurfaces. While metasurfaces have reached widespread popularity, their design is often based purely on the results of numerical simulations which can overlook many of the real-world fabrication imperfections. Being able to verify the real phase response of a fabricated device is of great utility for high-performance devices. Here, we use holographic microscopy to validate metalibraries of rectangular TiO2 and Si building blocks. Illumination effects are studied for wavelengths from 600 to 740 nm and linear polarization rotating within the full range of unique states (0 to 180deg). Finally, by varying the numerical aperture of the condenser lens from 0.05 to 0.5 we also study the effects of an off-axis illumination. Comparing the experimental results with simulations from finite-difference time-domain and rigorous coupled-wave analysis, we highlight the limitations of these theoretical predictions and underscore the utility of an experimentally established library of building blocks. We demonstrate that our proposed method of holographic microscopy is both practical and effective for creating a metalibrary that accounts for all fabrication and material imperfections, which is crucial for designing high-efficiency metasurfaces.

physics.optics↗