We report on optically pumped green stimulated emissions from regular nanocolumn arrays. Various InGaN-based triangular-lattice nanocolumn arrays with different lattice constants and nanocolumn diameters were prepared on a (0001) GaN/c-sapphire template using selective-area growth by rf-plasma-assisted molecular-beam epitaxy. The nanocolumn arrays were optically pumped at room temperature, and sharp peaks of stimulated emission were observed at green color wavelengths from 530 to 560 nm. The wavelengths varied with the photonic band edge, which was determined by the structural parameters of the nanocolumn arrays. The photonic crystal effect occurred, with the periodic arrangement of the nanocolumns contributing to the stimulated emission.

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Kinetic theory for dilute inertial suspension having soft-core potential is theoretically investigated. From the analysis of the scattering process, the expression of the scattering angle is analytically obtained. We derive the flow curve between the viscosity and the shear rate, which shows two-step discontinuous shear thickening when we change the softness of the particles. The molecular dynamics simulation shows that our theoretical results are consistent with the numerical ones.

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