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This paper investigates quenching solutions of an one-dimensional, two-sided Riemann–Liouville fractional order convection–diffusion problem. Fractional order spatial derivatives are discretized using weighted averaging approximations in conjunction with standard and shifted Grünwald formulas. The advective term is handled utilizing a straightforward Euler formula, resulting in a semi-discretized system of nonlinear ordinary differential equations. The conservativeness of the proposed scheme is rigorously proved and validated through simulation experiments. The study is further advanced to a fully discretized, semi-adaptive finite difference method. Detailed analysis is implemented for the monotonicity, positivity and stability of the scheme. Investigations are carried out to assess the potential impacts of the fractional order on quenching location, quenching time, and critical length. The computational results are thoroughly discussed and analyzed, providing a more comprehensive understanding of the quenching phenomena modeled through two-sided fractional order convection-diffusion problems. 

Hybrid photonic integration provides a platform to design and implement novel functionalities unavailable to active or passive material systems alone. We present an automated alignment and assembly process for hybrid-integrated laser systems, comprising silicon nitride (Si₃N₄) photonic integrated circuits (PICs) edge-coupled to gallium arsenide (GaAs) gain chips (GCs). We design and optimize spot size converters (SSCs) to increase the alignment tolerances between the PICs and GCs. Our automated assembly process has achieved experimental coupling losses of 2.7 dB between the PICs and GCs, closely matching the simulated values. Packaged hybrid lasers, when coupled to a lensed fiber, exhibit slope efficiencies of ∼ 97 mW/A. These results show the feasibility of scaling the production and widespread application of these hybrid laser systems by automating their assembly, which should drive down packaging costs and accelerate research. 

A preservative scheme is presented and analyzed for the solution of a quenching type convective-diffusion problem modeled through one-sided Riemann-Liouville space-fractional derivatives. Properly weighted Grünwald formulas are employed for the discretization of the fractional derivative. A forward difference approximation is considered in the approximation of the convective term of the nonlinear equation. Temporal steps are optimized via an asymptotic arc-length monitoring mechanism till the quenching point. Under suitable constraints on spatial-temporal discretization steps, the monotonicity, positivity preservations of the numerical solution and numerical stability of the scheme are proved. Three numerical experiments are designed to demonstrate and simulate key characteristics of the semi-adaptive scheme constructed, including critical length, quenching time and quenching location of the fractional quenching phenomena formulated through the one-sided space-fractional convective-diffusion initial-boundary value problem. Effects of the convective function to quenching are discussed. Numerical estimates of the order of convergence are obtained. Computational results obtained are carefully compared with those acquired from conventional integer order quenching convection-diffusion problems for validating anticipated accuracy. The experiments have demonstrated expected accuracy and feasibility of the new method. 

Metal halide perovskites represent a promising class of gain media for next‐generation nonepitaxial laser diodes. However, fully electrically pumped perovskite laser diodes have not been achieved yet. Herein, the use of sodium fluoride (NaF) is explored as an efficient additive in halide perovskite films to improve their optical and light amplification properties. The incorporation of NaF in perovskites leads to a remarkable threefold increase in light‐emitting intensity. The threshold of amplified spontaneous emission (ASE) by optical pumping is reduced by more than 20%, from ≈13.5 to 10.4 μJ cm⁻². Furthermore, the NaF‐modified perovskites exhibit stable ASE emission, even after exposure to 1.5 billion optical pulses, highlighting substantial improvements in the material's photostability. Finally, optically pumped ASE is observed from a full perovskite light‐emitting diode stack, including lossy metal electrodes. This work demonstrates significant progress toward the development of electrically pumped perovskite lasers. 

The aims of this paper are to investigate and propose a numerical approximation for a quenching type diffusion problem associated with a two-sided Riemann-Liouville space- fractional derivative. The approach adopts weighted Grünwald formulas for suitable spatial discretization. An implicit Crank-Nicolson scheme combined with adaptive technology is then implemented for a temporal integration. Monotonicity, positivity preservation and linearized stability are proved under suitable constraints on spatial and temporal discretization parameters. Two specially designed simulation experiments are presented for illustrating and outreaching properties of the numerical method constructed. Connections between the two-sided fractional differential operator and critical values including quenching time, critical length and quenching location are investigated.