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Journal of Physics D: Applied Physics - latest papers

Latest articles for Journal of Physics D: Applied Physics

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  • Ablation of cathode material heated by high current, high energy transient arcs under different ambient pressure
    This study investigates the evolution of transient arc plasma and its ablation behavior of cathode (initial) material under high-power electric pulse, addressing the issue of material ablation control arising from localized thermal gradients and phase transitions during plasma-condensed-matter interactions. Experiments were conducted using a pin-plate gas gap breakdown at varying ambient pressures. The discharge process was diagnosed using synchronized high-speed photography and voltage/current/photoelectric probes. Following discharge channel formation, plasma expansion was observed with an initial velocity of 2–3 km s−1, evolving from a spherical shape into an inverted bell shape, subsequently contracting into an inverted funnel configuration, accompanied by the plasma ejection in form of electrode spots. Increasing the discharge current from 15.4 kA to 21.9 kA resulted in a ∼90% increase in plasma radiation intensity. Reducing the ambient pressure led to increased dispersion and weakened radiation intensity of the plasma channel. Post-discharge ablation morphology observations revealed concentrated ablation with distinct regions at 0.1 MPa. Pressure, contrasting with a speckle pattern and significantly reduced surface roughness (Ra decreasing from ∼2.5 μm to < 0.5 μm) at lower pressure of 0.02 MPa. Inspired by these findings, the study explored and validated the arc-root dispersion effect and ablation homogenization capability of metal foams.

  • Ultralow-threshold single-mode quantum-dot laser operating at O-band based on bound-states in the continuum
    Light sources for generation of optical angular momentum (OAM) are popular on telecommunication systems and in demand for key telecommunications platforms, including on-chip ultra-compact integrated communication systems, free-space optical communication and optical fiber networks. Here, we demonstrate an ultralow-threshold laser based on optical bound states in the continuum (BIC), which serves as an ideal light source for generation of beams with OAM. In this context, given semiconductor material stability and robustness, the proposed BIC laser, comprising an InAs/GaAs quantum-dot (QD) active region and lasing at a wave-length of ∼1.3 μm, is characterized by a power threshold of 7.5 μW (0.038 kW cm−2) at room temperature. Moreover, our experimental measurements and computational analysis of the generated optical field reveal the vortex nature of the optical beam, as well as its non-trivial topological properties. This work demonstrates an energy-efficient, stable, and versatile single-mode QD BIC laser, which, as a source of optical vortex beams with large light extraction efficiency, offers great potential to facilitate high-capacity data transmission in future optical communication systems.

  • Second-order nonlinear generation for electric fields propagating in two spatial dimensions
    A derivation is conducted in two spatial dimensions to obtain the electric field pulse generated through second-order nonlinear processes, given electric fields incident onto a non-centrosymmetric crystal at a non-normal angle. Within this detailed derivation, it is necessary to perform a two-dimensional evaluation of the second-order nonlinear wave equation and allow the electric fields (along with their varying spectral components) to propagate through the crystal at different angles. The derived equations are employed within a representative example to depict electric field generation from a GaSe crystal, whereby we consider various incident angles and provide a comparison between theory and experiment. The developed model has the ability to evaluate sum frequency generation and difference frequency generation in any non-centrosymmetric crystal for electric fields at any incident angle.

  • Instantaneous deposition of functional coating with adjustable wettability via multi-phase thermal plasma jet
    Electrical explosion of metal wire comes with high-density thermal plasmas that can generate multiscale micro-nano surface structures benefiting functional performance in many scenarios. In this paper, supersonic plasma jet has been achieved via electrical explosion of a Cu wire, enabling ‘single-step’ fabrication of high-quality super-hydrophilic coatings (⩽6° contact angle). Then, we optimize the plasma premixing chamber by adding non-metal particles (40–260 μm), resulting in a multiphase jet comprising continuous-phase plasma and dispersed-phase solid particles. The deposited composite coating with distinct structural and compositional heterogeneity exhibits evidently hydrophobic properties (152.3°±3.3 contact angle). To find out more physical details, high-speed photography is adopted to reveal jet dynamics (speed 0.6 km s−1 at kJ-level discharge energy) and coating deposition process (5 ms). Supersonic plasma jet brings small particles (e.g., diamond) that impact the sample surface, forming robust mechanical interlocking. Simultaneously, metal plasma undergoes attachment, nucleation, and stacking-melting processes, establishing consolidated metallurgical bonding structures. Microscopic characterization further confirms composite coatings with micron-scale non-metallic particles and micro-nano metallic particulates. By modulating premixed particle sizes and plasma discharge parameters, tunable wettability across a broad range (95°–152°) is achieved, resulting in hydrophobic coatings. This study demonstrates the tunability of ‘one-step method’ prepared hydrophilic/hydrophobic metal coatings. By adjusting the ratio of non-metallic particles to metal wires, coatings with varying hydrophilicity/hydrophobicity can be obtained. This approach enhances coating preparation efficiency while further expanding the applicability range of the design.

  • Enhanced dielectric properties of PVDF-based three-phase composite films through introducing the semiconductive ZnO and ferroelectric NKBT filler
    Three-phase composites have emerged as a research focus in advanced electronic manufacturing due to their high permittivity, low loss, flexibility, and unique integration capabilities. In this study, ZnO-Na0.25K0.25Bi0.5TiO3/PVDF three-phase composites with varying filler contents were prepared through the solution-casting method. The incorporation of ZnO particles increased the content of the β-phase in PVDF, directly enhancing permittivity (ϵ′). The ϵ′ of the composites increased with increasing content of the filler, achieving an ϵ′ of 164 with a low tanδ of 0.12 at a volume ratio of 0.5. Moreover, the film exhibited a large breakdown strength of 359.5 kV mm−1 and excellent flexible properties. The enhancement in ϵ′ could be attributed to the interfaces of ZnO-PVDF and NKBT-PVDF, which created space charge accumulation that strengthened interfacial polarization. The dielectric response of ZnO-NKBT/PVDF composites was governed by the effective medium percolation theory model, with the ϵ′ dependence on filler content closely aligning with its theoretical predictions. This study provides a basis for the design of three-phase composites with high permittivity and low loss via interface regulation and model optimization.