In this study, the magneto-hydrodynamic boundary-layer flow and thermal convection of the Casson fluid with a ternary nanofluid mixture over a vertical cone is presented. The Casson model is used for modeling non-Newtonian yield stress fluids, which are present in polymeric and industrial fluids. The effects of an external magnetic field, thermal and momentum slip conditions, and non-uniform heat source/sink are considered, and the model is applicable to realistic thermal processing and energy applications. Conservation of mass, momentum, and energy equations are derived in the vertical cone geometry and converted to a dimensionless similarity form. Accurate velocities and temperatures inside the boundary layer are numerically calculated with the resulting nonlinear system solved numerically by a stable finite-difference method. Results show that because of the applied magnetic field, the fluid motion is slowed down in the boundary layer, and the thermal energy in the same region is increased by a resistive Lorentz force. The addition of ternary nanoparticles resulted in remarkable improvements in effective thermal conductivity and, hence, better heat transfer performance as compared to traditional fluids. With the help of momentum slip, the wall shear stress is reduced, while thermal slip enhances the reduction of the surface heat transfer rate. Moreover, the heat source parameter is non-uniform and increases the field of temperature, and the heat sink parameter decreases the field of temperature. The interplay of magnetic forces, Casson rheology, ternary nanoparticle effects, and slip mechanisms is of crucial importance to control the convective heat transfer over a vertical cone.
The presence of flicker noise in graphene-based Hall sensors (GHSs) with high Hall sensitivity degrades the signal-to-noise ratio for the detection of low-frequency magnetic signals. We report the design and characterization of a local back-gated GHS that achieves record-low flicker noise magnitude and corner frequency. These unprecedented noise levels are enabled by a modified fabrication process flow that suppresses effective trap density near the graphene channel. We report the measured record-low bias and area-normalized noise densities at 10 Hz for the driving and sensing terminals as 4.6 × 10−13 and 7.33 × 10−14 μm2 Hz−1, respectively. This translates to flicker-noise corner frequencies calculated as 32.5 and 0.6 Hz at the driving and sensing terminals, respectively. Furthermore, using results from adjoint network analysis for a generalized two-dimensional Hall structure, we correlate the flicker noise behaviors at the sensing and driving terminals of the GHS. To understand the origin of flicker noise in our fabricated devices, we study the noise contributions separately from the channel and contact regions by independently modulating each region through the local and global back gates, respectively. This analysis identifies the channel region as the primary source of flicker noise. Within the channel, to understand the dominant fluctuation mechanism in our devices, i.e., either carrier number or mobility fluctuations, we perform systematic investigation, through variations in carrier density, magnetic field, and temperature, at both the driving and sensing terminals, the latter being of particular relevance to the Hall sensor architecture. These measurements collectively support mobility fluctuations as the dominant mechanism. Moreover, to demonstrate the thermal-noise-floor-limited detection of low-frequency magnetic fields below the flicker noise corner frequency, we report, for the first time, the integration of the spinning current technique (SCT) with GHS. We achieve a current-normalized Hall sensitivity of 847 V/A T and a thermal noise floor of 29 nV/Hz using SCT, equivalent to a magnetic field noise spectral density of 342 nT/Hz.
Halide perovskite nanocrystals (PNCs) have attracted considerable interest due to their exceptional optoelectronic properties, presenting significant application potential across wide fields, particularly in optoelectronics. However, conventional synthesis methods face challenges in achieving sufficient precision, environmental sustainability, and reproducibility, which limit the advancement and practical implementation of these materials. Femtosecond (Fs) laser processing technology provides a novel and versatile approach for precise manipulation of perovskite materials, enabling controlled formation of diverse morphologies, dimensions, bandgaps, and complex nanoarchitectures, which is expected to accelerate the development and deployment of halide perovskites. This review presents a comprehensive synthesis of recent advances in fs laser-based processing of halide perovskite nanomaterials and their applications in optoelectronic devices. First, it examines the underlying mechanisms and strategies by which fs lasers induce nucleation, growth, bandgap tuning, and defect engineering of PNCs. Subsequently, the application of these engineered nanocrystals in light-emitting diodes (LEDs), lasers, and optical data storage is critically reviewed. Finally, the article highlights key future research directions and outstanding challenges in the field, aiming to provide essential theoretical insights and strategic guidance for the continued advancement of perovskite-based technologies.
This review provides a device-oriented, mechanism-based framework for understanding how two-dimensional Moiré superlattices can be engineered toward full-infrared photodetection from the NIR to the THz regime. This review evaluates the use of twist-angle-tunable two-dimensional Moiré superlattices as a platform for quantum cascade systems. In contrast to conventional III–V multi-quantum-well technologies that rely on fixed energy states, the Moiré-based approach provides a versatile alternative by utilizing Moiré-induced electronic states to enable tunable bandgap engineering. This study presents a comprehensive evaluation of four primary mechanisms that enable full-spectrum detection from the near-infrared to the THz range: direct injection, hot-electron emission, plasmonic oscillation, and quantum cascade processes. By integrating these physical mechanisms, we propose a silicon-compatible, all-infrared detection strategy that overcomes the material constraints associated with conventional semiconductor-based systems. Finally, this review identifies the key technical challenges that must be addressed for practical implementation, including the precise control of the twist angle, scalable large-area fabrication, and improved interfacial quality. Future progress is discussed through several promising approaches, including strain engineering, remote Coulomb modulation, and machine-learning-assisted structural design. These strategies provide a forward-looking roadmap for the development of next-generation high-performance infrared optoelectronic devices.
Optical vortex beams carrying orbital angular momentum provide a fundamental degree of freedom for structured light in space. Recent advances in ultrafast laser technology have extended optical vortices into the ultrafast and ultra-intense regime, where ultrashort pulse durations are combined with extremely high peak intensities. Such beams enable access to ultrafast, nonlinear, and strong-field light–matter interaction regimes, thereby unlocking emerging applications including laser-driven particle acceleration, micro- and nanofabrication, molecular detection, high-capacity optical communication and encryption, and advanced imaging. Motivated by these unique characteristics and exceptional application potential, this review article provides a comprehensive overview of ultrafast and ultra-intense optical vortices. We summarize key approaches for generation of ultrafast optical vortices using extracavity and intracavity techniques, discuss amplification strategies toward ultra-intense optical vortices, and review representative nonlinear and strong-field phenomena arising from vortex beam-matter interactions, together with recent advances in spatiotemporal characterization. Emerging applications are then highlighted, followed by a discussion of current challenges and future perspectives.
