A novel theoretical model of thermal diffusion has been established to study thermal interaction between two neighboring diodes in semiconductor laser arrays. The main cause of the ocurrence of the thermal interaction...A novel theoretical model of thermal diffusion has been established to study thermal interaction between two neighboring diodes in semiconductor laser arrays. The main cause of the ocurrence of the thermal interaction between two neighboring diodes in array devices is the heat conduction through heat sink. We hold that as the devices must have heat sink to diffuse heat, this kind of interaction in the array would always exist. However, when the pitch between two neighboring diodes in the array is reasonably defined, this troublesome thermal interaction can be simply reduced by using our model. Based on the individual diodes with leaky waveguide structure, we experimentally succeeded in fabricating 2D 4 ×4 arrays. The thermal interaction between upper and lower diodes in the 2D array is also considered as well as the function of the heat sink. The measured results show that the pulse peak output powor of the 2D 4 ×4 array is high up to 11 W.展开更多
Heat and energy are conceptually different, but often are assumed to be the same without justification. An effective method for investigating diffusion properties in equilibrium systems is discussed. With this method,...Heat and energy are conceptually different, but often are assumed to be the same without justification. An effective method for investigating diffusion properties in equilibrium systems is discussed. With this method, we demonstrate that for one-dimensional systems, using the indices of particles as the space variable, which has been accepted as a convention, may lead to misleading conclusions. We then show that though in one-dimensional systems there is no general connection between energy diffusion and heat conduction, however, a general connection between heat diffusion and heat conduction may exist. Relaxation behavior of local energy current fluctuations and that of local heat current fluctuations are also studied. We find that they are significantly different,though the global energy current equals the globe heat current.展开更多
We present a general homogenization method a periodic heterogeneous material with piecewise constants for diffusion, heat conduction, and wave propagation in The method is relevant to the frequently encountered upsca...We present a general homogenization method a periodic heterogeneous material with piecewise constants for diffusion, heat conduction, and wave propagation in The method is relevant to the frequently encountered upscaling issues for heterogeneous materials. The dispersion relation for each problem is first expressed in the general form where the frequency co （or wavenumber k） is expanded in terms of the wavenumber k （or frequency ω）. A general homogenization model can be directly obtained with any given dispersion relation. Next step we study the unit cell of the heterogeneous material and derive the exact dispersion relation. The final homogenized equations include both leading order terms （effective properties） and high order contributions that represent the effect of the microscopic heterogeneity on the macroscopic behavior. That effect can be lumped into a single dimensionless heterogeneity parameter β, which is bounded between -1/12≤β≤ 0 and has a universal expression for all three problems. Numerical examples validate the proposed method and demonstrate a significant computational saving.展开更多
文摘A novel theoretical model of thermal diffusion has been established to study thermal interaction between two neighboring diodes in semiconductor laser arrays. The main cause of the ocurrence of the thermal interaction between two neighboring diodes in array devices is the heat conduction through heat sink. We hold that as the devices must have heat sink to diffuse heat, this kind of interaction in the array would always exist. However, when the pitch between two neighboring diodes in the array is reasonably defined, this troublesome thermal interaction can be simply reduced by using our model. Based on the individual diodes with leaky waveguide structure, we experimentally succeeded in fabricating 2D 4 ×4 arrays. The thermal interaction between upper and lower diodes in the 2D array is also considered as well as the function of the heat sink. The measured results show that the pulse peak output powor of the 2D 4 ×4 array is high up to 11 W.
基金the National Natural Science Foundation of China (Grant Nos. 10925525, 11275159 and 10805036)the Specialized Research Fund for the Doctoral Program of Higher Education (Grant No.20100121110021)
文摘Heat and energy are conceptually different, but often are assumed to be the same without justification. An effective method for investigating diffusion properties in equilibrium systems is discussed. With this method, we demonstrate that for one-dimensional systems, using the indices of particles as the space variable, which has been accepted as a convention, may lead to misleading conclusions. We then show that though in one-dimensional systems there is no general connection between energy diffusion and heat conduction, however, a general connection between heat diffusion and heat conduction may exist. Relaxation behavior of local energy current fluctuations and that of local heat current fluctuations are also studied. We find that they are significantly different,though the global energy current equals the globe heat current.
文摘We present a general homogenization method a periodic heterogeneous material with piecewise constants for diffusion, heat conduction, and wave propagation in The method is relevant to the frequently encountered upscaling issues for heterogeneous materials. The dispersion relation for each problem is first expressed in the general form where the frequency co （or wavenumber k） is expanded in terms of the wavenumber k （or frequency ω）. A general homogenization model can be directly obtained with any given dispersion relation. Next step we study the unit cell of the heterogeneous material and derive the exact dispersion relation. The final homogenized equations include both leading order terms （effective properties） and high order contributions that represent the effect of the microscopic heterogeneity on the macroscopic behavior. That effect can be lumped into a single dimensionless heterogeneity parameter β, which is bounded between -1/12≤β≤ 0 and has a universal expression for all three problems. Numerical examples validate the proposed method and demonstrate a significant computational saving.
