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A numerical analysis of a quantum directional coupler based on Π-shaped electron waveguides is presented with use of the scattering-matrix method. After the optimization of the device parameters, uniform output for the two output ports and high directivity are obtained within a wide range of the electron momenta. The electron transfer in the device is found more efficient than that in the previously proposed structures. The study of the shape-dependence of transmission for the device shows that the device structure with smooth boundaries exhibits a much better performance. [ABSTRACT FROM AUTHOR]

The photoluminescence (PL) properties of ZnSe films grown by hot wall epitaxy are reported. The PL spectra show clear neutral donor-bound exciton peak; donor acceptor pair (DAP) peak, conduction band to acceptor (CA) peak, and their phonon replicas until fourth order. The conduction band to acceptor peak and it's phonon replicas exist until room temperature. From the ratio of PL intensities of DAP and CA peaks and their replicas, we obtain the Huang–Rhys factor S=0.58, in agreement with other experiments for acceptor-bound exciton transitions. From the temperature dependence of PL intensities we derive the activation energy of thermal quenching process for the DAP transitions as about 7 meV. [ABSTRACT FROM AUTHOR]

We report both experimentally and theoretically that asymmetric acoustic transmission is realized by an open channel with two triangle cavities of different sizes on each side immersed in air. This exotic phenomenon stems from asymmetric multiple scatterings induced by the triangle cavities, which is different from the previous devices based on acoustic metasurfaces. In addition, the influences of the temperature and machining inaccuracies on the asymmetric transmission effect are investigated in detail, and the asymmetric acoustic transmission still exists with the excitation of the cylindrical acoustic source. Our device is very simple and easy to be realized, and opens a new way to design the devices of the asymmetric acoustic transmission, which has great potential applications in acoustic rectifiers and acoustic diodes. [ABSTRACT FROM AUTHOR]