Performance improvement of nitride semiconductor-based deep-ultraviolet laser diodes with superlattice cladding layers

A deep-ultraviolet (DUV) laser diode (LD) consisting of specifically designed cladding layers involving superlattice nitride alloy has been proposed. Simulation studies of different cladding layers were carried out using Crosslight software. It was found that the proposed structure effectively suppresses the leakage of the optical field from the active region and the optical confinement coefficient is 1.45 times higher than that of the conventional structure. The proposed structure has a significant increase in laser power with a low threshold current. Moreover, the introduction of novel cladding layer suppresses the electron and hole leakage from the multiple quantum well (MQW) region, which provides an attractive solution for increasing the stimulated recombination rate in the MQW region leading to the improvement in the performance of the DUV LD

Age Structure and Body Size of The Tibetan Toad (Bufo tibetanus) Populations from Two Different Altitudes in China

Knowledge about the altitudinal patterns in age and body size helps to highlight the evolution of life history parameters in animals. In this study, we investigated the demographic traits of the Tibetan toad (Bufo tibetanus) between populations from low and high altitude habitats (2650 vs 3930m) using skeletochronology. We found 1) the mean age and body size of females were significantly greater than those of males in either population; 2) both sexes of toads from the higher altitude tended to be significantly older in age and larger in body size; 3) a significant positive relationship between age and body size within each sex of the toad at both altitudes; 4) growth rates varied between the two populations, with the higher rate observed in the low-altitude population, and lower in the high-altitude population. Our results suggest that factors other than age can influence altitudinal patterns in body size, such as altitude-associated temperature. Future research should pay attention to these factors and evaluate their influences on the growth patterns of animals.Knowledge about the altitudinal patterns in age and body size helps to highlight the evolution of life history parameters in animals. In this study, we investigated the demographic traits of the Tibetan toad (Bufo tibetanus) between populations from low and high altitude habitats (2650 vs 3930m) using skeletochronology. We found 1) the mean age and body size of females were significantly greater than those of males in either population; 2) both sexes of toads from the higher altitude tended to be significantly older in age and larger in body size; 3) a significant positive relationship between age and body size within each sex of the toad at both altitudes; 4) growth rates varied between the two populations, with the higher rate observed in the low-altitude population, and lower in the high-altitude population. Our results suggest that factors other than age can influence altitudinal patterns in body size, such as altitude-associated temperature. Future research should pay attention to these factors and evaluate their influences on the growth patterns of animals