中红外下半导体掺杂调制的表面等离子体透射增强效应

Enhanced mid-infrared transmission in heavily doped n-type semiconductor film based on surface plasmons

理论研究了平面电磁波通过n型重掺GaAs薄膜的透射谱.当GaAs薄膜两表面刻上亚波长的周期性沟槽结构时,透射谱在中红外波段出现了异常的透射增强现象.把这一现象归因于表面等离子体模式和波导模式的耦合.通过优化结构参数可以得到最大的透射效率.此外,发现随着掺杂浓度的升高,透射谱线中的透射峰逐渐向高频方向移动,最优化后透射峰值随掺杂浓度的升高而逐渐降低.这是由于掺杂浓度的改变,导致了不同的等离子体频率和电子碰撞频率,从而影响了激发模式和薄膜对电磁波的吸收.

Transmission of electromagnetic wave in a heavily doped n-type GaAs film is studied theoretically.From the calculations,an extraordinary transmission of p-polarized waves through the film with subwavelength grooves on both surfaces at mid-infrared frequencies is found.This extraordinary transmission is attributed to the coupling of the surface-plasmon polariton modes and waveguide modes.By selecting a set of groove parameters,the transmission is optimized to a maximum.Furthermore,the transmission can be tuned by dopant concentrations.As the dopant concentration increases,the peak position shifts to higher frequency but the peak value decreases.