arXiv subjects

Zhaona Wang

Publications and source records attributed to Zhaona Wang.

10 recordsLinked to original sources

arXiv2026

Reconfigurable Momentum-space vectorial lasing enabled by Quasi-BIC

Bound states in the continuum (BICs) have enabled lasers with rich momentum-space textures. However, the output patterns of quasi-BIC lasers remain largely static and confined to a few geometries. Here, a reconfigurable momentum-space vectorial laser was proposed based on two-dimensional photonic crystal. By selectively exciting quasi-BIC modes, we identify the geometric asymmetry factors favoring single BIC, dual-BIC, and radiative mode with BIC operation. This approach yields vectorial lasing with characteristic patterns lasing in momentum space of bidirectional double lobes (BDL), radially polarized ring with BDL, azimuthally polarized ring with BDL, and linearly polarized spot with BDL. Importantly, reversible switching between a single donut and a donut with BDL was achieved in the same device by varying the pump energy density. Our work establishes a compact, versatile platform for reconfigurable vectorial lasers, with potential applications in tunable optical tweezers, super-resolution imaging, and on-chip optical interconnects.

physics.optics↗

arXiv2026

Reconfigurable and Recyclable Low-Threshold Quasi-BIC Lasers via a Tunable polymer Coating

Reconfigurable and sustainable microcavity lasers are highly desirable for next-generation integrated photonics. Here, we report a recyclable, low-threshold quasi-bound state in the continuum (q-BIC) laser fabricated via low-cost, high-throughput interference lithography. By introducing a polyvinyl alcohol (PVA) coating on a dye-doped photonic crystal, we suppress out-of-plane symmetry breaking, which reinforces optical confinement and reduces the lasing threshold. The q-BIC modes are further tuned through tailoring the refractive-index of the PVA layer by using Kramers-Kronig relation via Rhodamine 6G doping, demonstrating a wavelength shift of 7.14 nm and a sensitivity of 215 nm RIU as a sensing prob. More importantly, lasing modes are reversibly tuning via precisely controlling the coating thickness. Exploiting the dissolving and re-coating process, the laser is repeatedly reconfigured while maintaining performance. This work provides a sustainable and adaptive platform for sensing and reconfigurable photonic systems.

physics.optics↗

arXiv2026

Spatiotemporal Topological Phase Transition in non-Hermitian Photonic System

While energy band topology in spatial photonic crystals (PCs) and momentum-band topology in temporal crystals have each served as powerful probes of topological phases in their respective domains, their unification in a static platform remains unexplored. In this Letter, we bridge this gap by introducing a waveguide assisted non-Hermitian SSH model, in which controlled tuning of loss and coupling drives PT-symmetry breaking and enables a continuous transition between energy- and momentum-gap regimes. This allows us to construct a complete spatiotemporal topological phase diagram in a unified parameter space. By mapping this phase diagram onto a spatially graded PC, we experimentally observe multiple Bloch momentum-band gaps and a continuous spatiotemporal topological transition via translating across the static sample, enabling real-time control over the evolution pathway of the band topology. Our work creates a versatile, bias-free platform for exploring synthetic spacetime physics and opens new avenues for controlling light via non-Hermitian band engineering.

physics.optics↗

arXiv2026

Dual Flat-Bands of Bound State in the Continuum and Radiative Mode via TE-TM Coupling

A general symmetry-controlled mechanism is proposed for realizing dual flat-bands of bound state in the continuum (BIC) and its radiative counterpart in photonic crystal slabs. By breaking the vertical mirror symmetry of slab, inter-polarization coupling between TE-like and TM-like modes is activated, while intra-polarization coupling among modes within the same polarization class is simultaneously preserved. The cooperative action of these two coupling channels gives rise to the concurrent flattening of both the BIC-hosting band and the radiative band, resulting in a dual flat-band system with strongly contrasting quality (Q) factors. An effective two-step coupling model is constructed to capture the essential physics and show that the emergence of the flat bands is governed by geometric tuning rather than accidental degeneracies. The mechanism is shown to be generic with respect to polarization and material platform, enabling dual flat-band states in both low- and high-index systems, with substantially enhanced angular bandwidths in the latter. These finding establish a unified route for flat-band photonic engineering and provide a robust platform for angle-tolerant resonant photonic functionalities.

physics.optics↗

arXiv2025

Dynamically Switchable Polarization Lasing between q-BIC and Bragg Resonance Modes

Quasi-bound states in the continuum (q-BICs) enable low-threshold lasing through high-Q cavity modes, yet their polarization tunability remains constrained by nanostructure-imposed cavity symmetries. By engineering a microcavity with an optimized duty cycle (0.34), we demonstrate a polarization-switchable distributed feedback (DFB) laser with controlled emission transitions between dual off-Γ q-BIC lasing and single Γ-point Bragg resonance (BR) lasing through switching pump polarization. The switching mechanism shows unprecedented robustness in varying waveguide thickness and photonic crystal period of DFB structures. Our findings extend the capabilities of DFB lasers beyond their conventional limits, opening opportunities for nanophotonics, classical and quantum optics applications.

physics.optics↗

arXiv2022

Generalized nanoscale electromagnetic boundary conditions and interfacial photonics

Classical electromagnetic boundary conditions (EMBCs) fail to describe quantum interface phenomena at nanoscale. Here, we construct the interface model with a transition layer describing the electromagnetic field inhomogeneity across the interface. Generalized nanoscale EMBCs are derived by introducing the magnetic interfacial response functions (IRFs) and are rewritten as three different forms based on Maxwell's equations in first order approximation. The corresponding Fresnel formula are further used to analyze the interfacial photonic phenomenon, demonstrating interesting behaviors of Brewster angle shifting, non-extinction at Brewster angle and distinctive non-classical absorption or gain effect at Brewster angle and the total internal reflection angles. IRFs-controlled GH-shifts of Gaussian beam near Brewster angle are generated by the non-classical interface. These unique phenomena give us some guidance to measure the IRFs and expand interface photonics in nanoscale.

physics.optics↗

arXiv2021

Random lasers with tunable angular spectra for high contrast imaging

Random lasers with low spatial coherence have important potential applications in high quality imaging and displaying. Here, a random laser with tunable angular spectra is proposed and fabricated through directly coupling an asymmetric microcavity with a commercial optical fiber. The designed random laser demonstrates pumping direction-independence property in working threshold, and good storage stability.More importantly, the angular spectrum can be adjusted by pumping different microcavities on the fiber, the output random lasing with ring-shape in momentum space are used as illumination source for biological imaging. An excellent image with speckle-free and higher contrast is achieved due to the low spatial frequency-free of the illumination source even relative to that of the common white lighting. The results indicate that the designed random laser has great application values in the fields of high-resolution biological imaging, integration optics and smart sensing.

physics.optics↗

arXiv2019

A color-switchable ring-shaped random laser in momentum space

A color-switchable random laser is designed through directly coupling random laser with a commercial optical fiber. By using a simple approach of selectively coating the random gain layer on the surface of fiber, the red and yellow random lasers are respectively achieved with low threshold and good emission direction due to the guiding role of optical fibers. Moreover, the unique coupling mechanism leads to the random lasing with ring-shape in momentum space, indicating an excellent illuminating source for high-quality imaging with an extremely low speckle noise. More importantly, random lasing with different colors can be flexible obtained by simply moving the pump position.

physics.optics↗

arXiv2018

Switchable plasmonic scattering of nanogaps for linewidth-tunable random lasing

Linewidth-tunable lasers have great application requirements in the fields of high-resolution spectroscopy, optical communications and other industry and scientific research. Here, the switchable plasmonic scattering of the metal particles with plenty of nanogaps is proposed as an effective method to achieve linewidth-tunable random lasers. By using the nonlinear optical effect of the environment medium, the metal particles demonstrate the transition from local scattering of nanogaps with high spatial frequency to traditional Mie scattering free from detail information with increasing the pump power density. Based on these two scattering processes, random lasers can be continuously driven from a narrow-linewidth configuration exhibiting nanogap effect dominated resonances to a broad-linewidth regime of collectively coupling oscillating among nanowires (or nanoflowers), demonstrating the dynamic range of linewidth exceeds two orders of magnitude. This phenomenon may provide a platform for further studying of the conclusive mechanism of random lasing and supply a new approach to tune the linewidth of random lasers for further applications in high-illumination imaging and biology detection.

physics.optics↗

arXiv2013

General laws of reflection and refraction for subwavelength phase grating

The general reflection and refraction laws at the metasurface with the abrupt phase shift were derived by two different methods of Fermat's principle and the boundary conditions respectively. It is found that one or two critical angles for total internal reflection exist when a light hits on the optical sparse material from the optical denser material, and one such a critical angle exists when light spreads from the optical sparse material to the optical denser material. Anomalous reflection and refraction, such as, negative reflection and negative refraction may occur when a light passes through the metasurface, and the conditions of their occurrence were given. Finally, a kind of metasurface based on one-dimensional phase mask was designed to control the light propagation.

physics.optics↗