arXiv subjects

Yun-Sheng Chen

Publications and source records attributed to Yun-Sheng Chen.

3 recordsLinked to original sources

arXiv2025

Uniform 2D Target Generation via Inverse-designed Metasurfaces

We propose an inverse design framework for metasurfaces that achieves highly uniform two-dimensional intensity profiles across an on-demand shape. The optimization objective is formulated to enhance overall projection efficiency via the adjoint method, while a regularization term penalizes local deviations in field amplitude to suppress intensity non-uniformity. The regularization weight is adaptively tuned based on the current non-uniformity, enabling stable and efficient optimization. Compared with the widely used mean squared error (MSE) objective, our method yields superior performance in both intensity fidelity and uniformity. We also extend our framework to handle realistic Gaussian beam illumination by biasing the library. Simulation results confirm the effectiveness of our approach for generating high-quality, uniform field patterns.

physics.optics↗

arXiv2023

Qi standard metasurface for free-positioning and multi-device supportive wireless power transfer

Free-positioning and multi-user supportive wireless power transfer systems represent the next-generation technology for wireless charging under the Qi standard. Traditional approaches employ multiple transmitting coils and multi-channel driving circuits with active control algorithms to achieve these goals. However, these traditional approaches are significantly limited by cost, weight, and heating due to their relatively low efficiency. Here, we demonstrate an innovative approach by using a metasurface to achieve free-positioning and multi-user compatibility. The metasurface works as a passive device to reform the magnetic field and enables high-efficiency free-positioning wireless power transfer with only a single transmitting coil. It shows up to 4.6 times improvement in efficiency. The metasurface also increases the coverage area from around 5 cm by 5 cm with over 40% efficiency to around 10 cm by 10 cm with over 70% efficiency. We further show that the system can support multiple receivers. Besides increasing the overall efficiency, we demonstrate tuning the power division between the multiple receivers, enabling compensation of receivers of different sizes to achieve their desired power.

physics.app-ph↗

arXiv2022

Understanding the Spatiotemporal Resolution of Near-Field Photoacoustics from Nanostructures

Understanding the mechanism of photoacoustic generation at the nano-scale is key to developing more efficient photoacoustic devices and agents. Unlike the far-field photoacoustic effect that has been well employed in imaging, the near-field profile leads to a complex wave-tissue interaction but is under-studied. Here we show that the spatiotemporal profile of the near-field photoacoustic waves can be shaped by laser pulses, anisotropy, and nanoparticle(s) spatial arrangement. Using a gold nanorod as an example, we discovered that the near-field photoacoustic amplitude in the short axis is ~75% stronger than the long axis, and the anisotropic spatial distribution converges to an isotropic spherical wave at ~50 nm away from the nanorod's surface. We further extend the model to asymmetric gold nanostructures by arranging isotropic nanospheres anisotropically with broken symmetry to achieve a precisely controlled near-field photoacoustic "focus" largely within an acoustic wavelength.

physics.bio-ph↗