金属光栅覆盖分布式布拉格反射镜结构的透射增强效应

Transmission enhancement effect of distributed Bragg reflector structure covered with metal grating

为了采用易于直接激发的塔姆等离激元(Tamm plasmon polaritons,TPPs)实现透射增强现象,本文提出了一种由一维金属光栅覆盖分布式布拉格反射镜(distributed Bragg reflector,DBR)构成的层状结构.采用有限元法分析了入射光波在DBR-金属交界面上激发TPPs并产生能量高度局域的物理过程.研究表明入射TM光波在金属-DBR交界面上激发的TPPs可以有效地激发金属狭缝内的SPPs模式,当SPPs模式在狭缝内满足类FP谐振的条件就可以使入射光波在该结构中的产生透射增强.在此基础上,分析了狭缝宽度及其占空比对透射谱峰的定量影响.结果显示:周期确定时随着狭缝宽度的增大,峰值透射率则呈现先增大后减小的变化趋势;宽度确定时随着占空比的增大,峰值透射率会呈现单调降低的变化趋势,而透射峰中心波长呈现近似线性蓝移趋势,这为灵活调节异常透射的中心波长提供了一种有效手段.

In order to observe the extraordinary optical transmission(EOT)through a metal gratings,induced by Tamm plasmon polaritons(TPPs),a layered structure consisting of a distributed Bragg reflector covered with a one-dimensional metal grating is proposed in this work.When an incident light wave passes through DBR regime and impinges on the DBR-metal interface normally,the generation of TPPs and the resulting highly localized energy on the metal-DBR interface are simulated in detail by the finite element method.As a result,the surface plasmon polariton(SPPs)modes accommodated inside the slits of metal gratings can be excited more effectively by the enhanced electromagnetic field associated with TPPs located on the interface.Furthermore,the enhanced transmission of incident light waves in the structure can be achieved when the SPP mode inside the grating slits satisfies the Fabry-Perot(FP)-like resonance condition,which reveals that the EOT in this structure comes from a TPPs-FP hybrid resonance.This inference can be confirmed by the relationships between the central wavelength and the grating height for the two transmission peaks,and the magnetic field modal profiles associated with the two peaks.Quantitative effects of the slit width and duty cycle on the transmission peak of the metal grating are analyzed numerically,and the results demonstrate that when the period is determined,as the slits width increases,the two peak transmittances first increase and then decrease.On the other hand,when the slit widths are chosen to be 40 nm,50 nm,and 60 nm respectively,the peak transmittance first increases and then decreases with the duty cycle increasing.Meanwhile,it is found that the center wavelengths of the transmission peaks are related to the duty cycle in a nearly linear manner for three slit widths,which can be used to flexibly adjust the center wavelength of extraordinary optical transmission.