用有效介质理论模拟Ag/AAO纳米有序阵列复合结构光学常数

运用Maxwell—Garnett有效介质理论，计算了Ag／阳极氧化铝（AAO）纳米有序阵列复合结构的光学常数（250～2000nm波段），探讨了Ag组分的体积分数对Ag／AAO光学常数的调制作用和Ag纳米粒子的长径比对其表面等离子共振吸收的影响．模拟结果表明，随着Ag组分体积分数的增加，在小于450nm波段，Ag／AAO复合结构的介电函数实部和折射率均逐渐减小，而介电函数虚部和消光系数逐渐增大；在大于450nm波段，Ag／AAO复合结构的介电函数实部、介电函数虚部及折射率均逐渐增大，消光系数则变化较小．模拟结果显示出Ag纳米粒子的长径比与复合结构表面等离子共振吸收峰位有较强的相关性．另外，理论模拟预期透射谱也与实验透射谱变化趋势一致．

Simulation of the optical properties of Ag/AAO nanoarrays composite with effective medium theory

By using Maxwell-Garnett effective medium theory,the optical constants of Ag/AAO nano-ordered array composites have been simulated,the dependence of optical constants of Ag/AAO composites on Ag volume fraction and the relationship between the aspect ratios of Ag nanoparticles and the surface plasmon resonance absorption(SPRA) of Ag nanoparticles have been studied.The simulated results show that the optical constants of Ag/AAO nanocomposites strongly depend on the Ag volume fraction.With the increasing of Ag volume fraction,the real part of the permittivity and the refractive index of Ag/AAO nanocomposites decrease,at the same time the imaginary part of permittivity and the extinction coefficient increase,in the wavelength range of 280~450 nm.However,the refractive index,the real part and imaginary part of permittivity of Ag/AAO nanocomposites increase,and there is almost no variation of the extinction coefficient in the region of 450~2000 nm.Furthermore,there are great influence of the aspect ratios of Ag nanowires on the surface plasmon resonance absorption(SPRA) of Ag nanowires.Meanwhile,the simulated transmittance of Ag/AAO nanocomposites is well agreement with the measured,which manifests the Maxwell-Garnett effective medium theory can simulate the optical properties of Ag/AAO nanocomposites effectively.