Zhanxu Chen

AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) suffer from low light extraction efficiency (LEE), primarily constrained by strong optical absorption in the p-GaN layer and total internal reflection (TIR), particularly for the dominant transverse-magnetic (TM) polarization. To address this, we introduce a dual-layer nanostructure design combining surface parabolic cones with embedded p-GaN nanopillars. We demonstrate that conventional layer-by-layer optimization (Strategy A) is limited by inefficient inter-layer mode coupling, whereas our proposed holistic co-optimization (Strategy B) utilizing particle swarm optimization (PSO)-based finite-difference time-domain (FDTD) simulations effectively harnesses the inter-layer synergistic effect. Results reveal that Strategy B boosts the total LEE to 12.98% at 280 nm. Crucially, the TM-mode extraction is enhanced by ∼36-fold (from 0.29% to 10.70%), effectively converting trapped lateral guided modes into upward extracted radiation. This work proves that holistic co-optimization is a necessity for maximizing the performance of coupled multi-parameter photonic devices.

The College physics experiment is a fundamental course for cultivating applied and innovative talents in science and engineering disciplines in universities. In the context of the construction of the Golden Course, in order to effectively improve the high-level, innovative, and challenging nature of practical courses, the course adopts a mixed online and offline teaching method, constructs a closed-loop practical teaching process based on the BOPPPS teaching model, emphasizing the student-centered teaching philosophy that stresses comprehensive student participation and feedback communication. Practice has shown that blended teaching based on the BOPPPS model can effectively utilize information technology teaching platforms and online teaching resources, breaking through the limitations of experimental courses such as class hours, venue, and number of students in experimental courses. Focusing on physics experiment projects, a closed-loop training of “guidance—objectives—pre testing—participatory learning—post testing—summary and expansion” is carried out both online and offline, which promotes the improvement of students' abilities in problem-solving, practical operation, and application innovation in multiple aspects.

In this paper, we construct a near-infrared Fabry–Perot cavity composed of two sodium (Na) layers and an antimony trisulfide (Sb₂S₃) layer. By cascading two Fabry–Perot cavities, the transmittance peak splits into two transmittance peaks due to the coupling between two Fabry–Perot modes. We utilize a coupled oscillator model to describe the mode coupling and obtain a Rabi splitting of 60.0 meV. By cascading four Fabry–Perot cavities, the transmittance peak splits into four transmittance peaks, leading to a near-infrared transparent band. The near-infrared transparent band can be flexibly tuned by the crystalline fraction of the Sb₂S₃ layers. In addition, the effects of the layer thickness and incident angle on the near-infrared transparent band and the mode coupling are investigated. As the thickness of the Na layer increases, the coupling strength between the Fabry–Perot modes becomes weaker, leading to a narrower transparent band. As the thickness of the Sb₂S₃ layer increases, the round-trip propagating of the Sb₂S₃ layer increases, leading to the redshift of the transparent band. As the incident angle increases, the round-trip propagating of the Sb₂S₃ layer decreases, leading to the blueshift of the transparent band. This work not only provides a viable route to achieving tunable near-infrared transparent bands, but also possesses potential applications in high-performance display, filtering, and sensing.

The demand for personalized lighting environments based on households is steadily increasing among users. This article proposes a novel intelligent control system for personalized lighting in home environments, aiming to automatically capture user information, such as homecoming time and light switching behavior, in order to train a model that intelligently regulates the lights for users. Facial recognition technology is employed by this system to identify users and record their lighting data. Subsequently, nine commonly used machine learning models were evaluated, revealing that the error back-propagation neural network algorithm exhibits excellent performance in time-series analysis. The BPNN weights were optimized using genetic algorithms, resulting in an improved coefficient of determination (R²) of 0.99 for turn-on time and 0.82 for turn-off time test sets. Furthermore, testing was conducted on data collection duration which demonstrated that even with only 20 time-series data collected from new users, the model still displayed exceptional performance in training prediction tasks. Overall, this system effectively identifies users and automatically adjusts the lighting environment according to their preferences, providing comfortable and convenient lighting conditions tailored to individual needs. Consequently, a broader goal of energy conservation and environmental sustainability can be achieved.

An intense terahertz laser field is shown to actively manipulate the electronic states, as well as the linear and nonlinear optical absorption coefficients, of the laterally-coupled quantum well wires (LCQWWs). The laser-dressed quantum states of the LCQWWs are achieved using the non-perturbative Floquet method and the two-dimensional diagonalization technique under the effective mass approximation. We have demonstrated that the intense terahertz laser field induces a strong deformation of the confinement potential configuration of the LCQWWs, thus pronouncedly dressing the energy levels and wave functions. An unambiguous picture is depicted for the evolution of the laser-dressed quantum states with the increase of the laser-dressed parameter characterizing the strength of the laser-dressed effect. On this basis, the resonant peak positions of the linear and nonlinear optical absorption coefficients feature a blue shift followed by a red shift with an increase of the laser-dressed parameter. Furthermore, the evolution of the peak values for the linear and third-order nonlinear optical absorption coefficients as a function of the laser-dressed parameter is comprehensively discussed. Moreover, in contrast to the case without intense terahertz laser field, the peak values of the linear, third-order nonlinear, and total optical absorption coefficients can be obviously enhanced at the same frequency position by manipulating the appropriate laser-dressed parameter. A similar feature can be found in the linear, third-order nonlinear, and total refractive index changes. Our findings are conducive to the implementation of the expected quantum states and nonlinear optical effects in the LCQWWs, paving the way for new designs in tunable optical switches, infrared photo-detectors and infrared modulators.

We studied the effects of the lattice pitch of indium-doped tin oxide (ITO) periodic nanostructures on the diffracted transmission to improve the light extraction efficiency of light-emitting diodes (LEDs). Periodic hexagonal ITO nanopillars with lattice constants of 600, 800, 1050, 1200, and 1600 nm were fabricated on ITO electrodes. We found that the light extraction efficiency strongly depended on the lattice constant. The LEDs with a lattice constant of 800 nm ITO nanopillars showed an increase in light extraction of 83%. In addition, their electrical properties were not degraded compared to conventional LEDs. The dependence of the extraction efficiency on the lattice constant was also calculated using a 3D finite-difference time-domain (FDTD) method, and this dependence was in good agreement with the experimental measurements. The transmission of each diffraction order and with the total transmission of ITO nanopillars with different lattice constants were calculated using the FDTD method to investigate the enhancement effect.

Various plasmonic nanocavities possessing an extremely small mode volume have been developed and applied successfully in the study of strong light-matter coupling. Driven by the desire of constructing quantum networks and other functional quantum devices, a growing trend of strong coupling research is to explore the possibility of fabricating simple strong coupling nanosystems as the building blocks to construct complex systems or devices. Herein, we investigate such a nanocube-exciton building block (i.e. AuNC@J-agg), which is fabricated by coating Au nanocubes with excitonic J-aggregate molecules. The extinction spectra of AuNC@J-agg assembly, as well as the dark field scattering spectra of the individual nanocube-exciton, exhibit Rabi splitting of 100–140 meV, which signifies strong plasmon–exciton coupling. We further demonstrate the feasibility of constructing a more complex system of AuNC@J-agg on Au film, which achieves a much stronger coupling, with Rabi splitting of 377 meV. This work provides a practical pathway of building complex systems from building blocks, which are simple strong coupling systems, which lays the foundation for exploring further fundamental studies or inventing novel quantum devices.

Optoacoustic tomography can be applied into medical imaging, which can detect the light absorption distribution of target hidden inside scattering media. When a short laser pulse illuminates the optical turbid media, such as biological tissue, the media will generate ultrasound pulses, which is linearly proportional to the optical absorption of the media. The acoustic pressure distribution can be imaged with an acoustic lens. Similar to an optically imaging system, the optoacoustic signals from a plane in tissue require the same delay time to reach a detecting plane. While the optoacoustic signals from different planes in media require different delay time to reach an image plane. A BOXCAR was used to go on with the same delay-time, and a 64-element linear transducer array was one-dimensional scanned on an imaging plane, and thus the acoustic pressure distribution was acquired. The signals were recorded and reconstructed by a computer. By scanning the sampling gate of BOXCAR, the optoacoustic images of different planes in media could be obtained. The experimental result indicates that the system is able to obtain optoacoustic tomography images of targets hidden optical turbid media, and the reconstructed images agree well with the original samples. The results show that the lateral resolution is about 5mm and the axial resolution is about 1.5mm.