arXiv subjects

Jui-Han Fu

Publications and source records attributed to Jui-Han Fu.

4 recordsLinked to original sources

arXiv2026

Finite-Size Effect Induced Spatial-Spectral Mode Splitting in Membrane Metasurfaces

This work reports the spatial-spectral engineering and finite-size quantization of optical modes within a triangular-lattice silicon nitride membrane metasurface. Truncating the lattice into a finite square cavity breaks translational symmetry and lifts modal degeneracy, splitting optical modes into discrete cavity-envelope sub-modes. High-resolution photoluminescence (PL) scanning reveals distinct spatial field distributions. The corner-localized sub-mode features the highest Q-factor due to multipolar far-field destructive interference, whereas the core-localized sub-mode exhibits strong radiative coupling. PL mapping reveals a symmetric, four-fold clover-like wavelength arrangement. These results demonstrate that boundary-induced deterministic symmetry can override underlying lattice characteristics, offering a robust strategy for precise spatial-spectral tailoring of light-matter interactions at the nanoscale.

physics.optics↗

arXiv2026

Freestanding Resist Metasurface Supporting Higher-Order BICs for Efficient Field Enhancement in TMD Monolayers

Enhancing light-matter coupling in two-dimensional (2D) semiconductors such as transition metal dichalcogenide monolayers remains a central challenge in nanophotonics due to their atomic thickness, which limits their interaction volume with light. Here, we demonstrate that first-order quasi-bound states in the continuum (quasi-BICs) supported by a freestanding metasurface provide exceptionally strong surface field enhancement, enabling efficient coupling with a tungsten disulfide (WS2) monolayer. Triangular-lattice polymer patterns on silicon nitride membranes are fabricated to realize these higher-order modes. Simulations reveal that first-order quasi-BICs exhibit much stronger field enhancement than zeroth-order modes at the top surface where the WS2 monolayer is placed. Photoluminescence (PL) measurements confirm a remarkable PL enhancement factor of 127 for first-order quasi-BICs, over six times larger than that of zeroth-order quasi-BICs. These results establish higher-order BICs in freestanding metasurfaces as a powerful route to engineer light-matter interactions in 2D semiconductors for advanced nanophotonic and quantum photonic applications.

physics.optics↗

arXiv2025

Large-Area Photonic Membranes Achieving Uniform and Strong Enhancement of Photoluminescence and Second-Harmonic Generation in Monolayer WSe2

Two dimensional transition metal dichalcogenides exhibit strong excitonic responses, direct bandgaps, and remarkable nonlinear optical properties, making them highly attractive for integrated photonic, optoelectronic, and quantum applications. Here, we present a large area freestanding membrane photonic platform that achieves exceptional enhancement of light matter interactions in monolayer WSe2 via quasi bound states in the continuum. The freestanding architecture effectively suppresses radiative losses and supports high Q optical resonances, leading to enhanced light matter interactions. This results in significant photoluminescence emission and second harmonic generation enhancement factors of 1158 and 378, respectively, with spatial uniformity sustained across a 450 times 450 um2 area. This uniform SHG enhancement further enables polarization resolved mapping of crystal orientation and grain boundaries, offering a practical method for large area structural characterization of 2D materials. Moreover, femtosecond pumped SHG spectra reveal multiple narrowband peaks originating from distinct quasi BIC modes providing direct spectral evidence of resonantly enhanced nonlinear coupling. The combined attributes of strong optical enhancement, spectral selectivity, and wafer scale compatibility establish this platform as a scalable interface for 2D semiconductor integration in next generation optoelectronic, nonlinear, and quantum photonic technologies.

physics.optics↗

arXiv2025

Atomic-Scale Light Coupling Control in Ultrathin Photonic Nanomembranes

Atomic-layer and two-dimensional (2D) materials have emerged as essential building blocks for next-generation quantum and semiconductor technologies, where atomic-scale control over light-matter interactions is critical. However, their inherently small interaction volume poses fundamental challenges for efficient integration into quantum and nanophotonic devices. Addressing this limitation requires the development of photonic platforms that can effectively enhance atomic-scale optical coupling. To this end, freestanding nanomembranes with extreme thinness and minimal radiative loss offer an ideal framework for integrating these materials into photonic systems. Here, we demonstrate an ultrathin photonic nanomembrane enabling atomic-scale control of light coupling. This architecture supports strong field confinement at the surface and significantly enhances light-matter interaction. Through the integration of atomic-layer dielectrics, we achieve {\AA}-level thickness modulation, where each deposition cycle leads to an ultrafine shift of the high-Q resonance. High-resolution spatial mapping further confirms uniform and deterministic resonance tuning across the nanomembrane surface. Furthermore, by integrating a WS2 monolayer with the photonic nanomembrane, strong field localization within the monolayer and a significant emission enhancement are achieved. This approach offers a scalable and versatile route for atomic-scale light coupling, helping to overcome the limitations of conventional photonics and opening opportunities in quantum photonics, optoelectronics, and advanced semiconductor technologies.

physics.optics↗