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We report significant improvements in threshold current density and maximum operating temperature in continuous wave (CW) operation of interband cascade lasers (ICLs) near 5 μm. The uncoated ICLs were demonstrated at room temperature with a threshold current density of 343.8 A/cm2 and an output power of 31 mW/facet at 25 °C in CW mode. Different ICLs made from the same wafer were compared to study the impact of device dimensions on performance. The threshold current density of 331 A/cm2 achieved from a facet-uncoated 5 mm-long device at 25 °C is the lowest among all previously reported room temperature CW ICLs with emission wavelengths longer than 4 μm. Compared to the previous record of 480 A/cm2 at 4.75 μm for a facet-coated 4-mm-long ICL at 25 °C, this value of 331 A/cm2 is reduced by 31%, representing a substantial improvement. Benefited from improved device fabrication and enhanced thermal dissipation, the maximum CW operating temperature of the device reached 66 °C, which is the highest ever reported for ICLs with similar emission wavelengths. [ABSTRACT FROM AUTHOR]

Water–air trans-media unmanned vehicle is a kind of aircraft, which can freely fly in the air, sail in the water and pass through free surface. For trans-media aircrafts, the development process from air–surface to air–underwater and from submarine-launched drive to autonomous drive is investigated. By analyzing the characteristic of manta ray, flying fish and existing aircraft, this paper proposes a new water–air trans-media unmanned vehicle with flat dish-airfoil-shaped main body and telescopic NACA-type wing. Then the numerical method to calculate the lift and drag forces is established and validated by the results of classic NACA cases. On this basis, the flow field around the new vehicle is numerically simulated, and its lift–drag performances in different media (air and water) and ground effect are analyzed, comparing it with a model inspired by the Blackwing Unmanned Aerial Vehicle (UAV). The findings illustrate the superior performance of the new vehicle in terms of lift and drag forces, offering an innovative design framework for water–air trans-media UAV applications. [ABSTRACT FROM AUTHOR]

For a fish tank of breeding vessels with perforated broadsides, in order to analyze its fluid characteristics under wave conditions, this paper presents a numerical method and predicts the fluid field in a fish tank with opening holes. Therein, three critical problems were solved, which include wave generation, the fluid–structure interaction of waves and vessel motion, and the sloshing phenomenon in the tank. The feasibility of the method was validated through a comparison with theoretical and experimental results. On this basis, the fluid characteristics in the fish tank of a fixed breeding vessel with opening holes on side walls were discussed. Firstly, the effects of wave direction, wave height, and wave period on the flow field in the tank were mainly analyzed. Next, the fluid characteristics in the tank of a floating vessel with opening holes equipping a multi-point mooring system were investigated. Finally, the influence of motion responses of breeding vessels on the fluid field in the fish tank was examined. [ABSTRACT FROM AUTHOR]

Erbium (Er)‐doped III‐V semiconductors are promising for optoelectronic devices due to the unique intra‐4f electronic transitions of Er3+; however, the Er‐related luminescence at room temperature has always been challenging to obtain. In this work, High crystalline quality ErAs:GaAs films are grown with self‐assembled ErAs nanoparticles embedded within the GaAs matrix by molecular beam epitaxy. Rich photoluminescence spectra in a broad wavelength ranging from near‐ultraviolet to near‐infrared are observed at room temperature and confirmed to be Er‐related. A carrier‐mediated energy transfer up‐conversion mechanism is proposed, and the pump power‐dependent photoluminescence results reveal that the excited‐state absorption is governed by a single photonic process. The efficient interaction and energy transfer between the semiconductor matrix and Er3+ ions offered by this unique nanocomposite material provide a promising route to achieve novel optoelectronic devices with the potential to cover a broad wavelength range. [ABSTRACT FROM AUTHOR]

The processing of green ceramics aims to obtain parts with complex shapes and good surface quality. This paper prepared tools with micro/nano‐textured flank face by femtosecond laser to improve the cutting performance in processing of Al2O3 green ceramics. The wear resistance of cutting tools and characteristics of machined compacts are analyzed. Results shows that textures can improve the wear resistance of cutting tools and surface quality of green ceramics. Micro/nano‐textured tools own the best cutting performance, the improvement rate of wear resistance and surface roughness can reach 28.5% and 25% respectively. The reasonable mechanisms are explained by the storage of powder chips and the derivative‐cutting phenomenon by textures. The derivative‐cutting behavior can prevent cutting tool from severe abrasive wear by hard phase particles. The storage function prevents the powder chips from scratching the unworn surface of cutting tools, and the additional scratching of the machined surface by the hard phase particles is reduced. The two functions contribute to the improvement of cutting performance of micro/nano‐textured tools. [ABSTRACT FROM AUTHOR]