Bin Chen

Second-order nonlinear optical susceptibilities in asymmetric coupled quantum wells

The second harmonic generation (SHG) in the asymmetric coupled quantum wells (ACQWs) is studied theoretically for different widths of the right-well and the barrier. The analytical expression of the SHG susceptibility is deduced by using the compact density matrix approach and the iterative method. Numerical calculations are presented for typical GaAs/AlxGa1−xAs ACQWs. The results show that the calculated SHG susceptibility in this coupled system can reach a magnitude of 10−5 m V−1, 1–2 orders higher than that in single quantum systems. Moreover, the SHG susceptibilities are not monotonic functions of the widths of the right-well and the barrier, but have complex relationships with them. The calculated results also reveal that by adjusting the widths of the right-well and the barrier respectively, a set of optimal structural parameters can be found for obtaining a strong SHG susceptibility.

Dot Pattern Designing on Light Guide Plate of Backlight Module by the Method of Molecular Potential Energy

An approach for dot pattern designing on the light guide plate of backlight module is proposed in this paper. The proposed approach employs molecular potential energy model to generate random-dot patterns for light guide designed for backlight systems. The methods of developing dot patterns are various. We chose AutoCAD-VBA programme method for its visible interface. The algorithm can be divided into two steps: Firstly, an AutoCAD-VBA programme is compiled to generate random initial dot patterns, which contains 69 091 points. Secondly, a variable equilibrium distances system are found by the Mathematica software to fine tune distances among those points. At last, we have derived dot patterns which can satisfy the uniformity luminance requirement demanded by liquid-crystal displays, testing results show that the optical uniformity can reach 89.3%.

INTERSUBBAND OPTICAL ABSORPTION IN CYLINDRICAL QUANTUM DOT QUANTUM WELL

The intersubband optical absorption in cylindrical quantum dot quantum well (QDQW) for different sizes of QDQW is theoretically studied. The analytical expression of the absorption coefficient is derived by using the compact density-matrix approach and the iterative method. And the numerical calculations are presented for a typical GaAs/AlGaAs QDQW. The results obtained show that the optical absorption coefficient in the QDQW can be importantly modified by size of shell well. Moreover, they also show that the optical absorption is strongly dependent on the incident optical intensity.