金微纳阵列表面等离激元中红外波段光谱特性

Spectral Characteristics at Mid-Infrared Wavelength Regime of Gold Micro-Nano Arrays Surface Plasmons

表面等离激元是金属表面自由电子在入射光激发下产生的电子集体振荡行为及其相应的电磁场分布。目前,金微纳颗粒表面等离激元除了在可见光波段内被大量研究和应用外,在中红外波段内也显示出独特的光谱特性,具备设计生产优良传感器的潜力,因而同样备受瞩目。研究表明,在中红外波段内设计表面等离激元传感器的关键问题在于如何有效地调节共振谱的共振波长、峰值吸收率以及半峰宽等主要特征参数。相比于单个微纳颗粒而言,阵列结构由于拥有良好的周期性,从而能够在上述参数的宽光谱调节方面具有独特的优势。基于此,提出一种基于金微纳颗粒组成的阵列结构,利用时域有限差分方法,在4～18μm波段范围内,通过分别改变该阵列的结构参数,包括颗粒半径、高度、间距及颗粒形状等,系统地研究了该微纳阵列结构在中红外波段对入射光的反射光谱、透射光谱和吸收光谱等特性的影响。研究发现,在8～10μm光谱内,入射光能够与其所激发的金微纳阵列表面等离激元产生共振效应,表现出明显的共振峰特性。可以通过分别改变上述结构参数来有效调节吸收率谱线共振峰的共振波长、峰值吸收率和半峰宽等主要特征参数。研究结果对中红外光谱内基于金微纳阵列结构传感器的科学研究和实际设计具有独特的理论应用价值。

Surface plasmons are collective oscillations of surface electrons in metal,as well as the related electro-magnetic fields,which are induced by incident lights.So far,the spectral characteristics of the surface plasmons of gold micro-nano particles have been widely studied and applied,at the visible light regime.In addition,the spectral properties in the mid-infrared wavelength region have also drawn great attention in the community,due to its great potential in the research of good-quality sensors.So far,to systematically adjust the paramters including the resonance wavelength,the maximum absorptance and the full width at half maximum intensity,etc.in the design of the surface plasmon-based photoelectric sensing devices,is still a key issue in the community.Compared with single paticles,array-based structures possess great advantages in tuning the above mentioned parameters due to the characteristics of periodicity.Therefore,in this work,an array structure based on gold micro-nano particles is proposed.With the finite difference time domain method,the reflectance spectrum,transmittance spectrum and absorptance spectrum in a wavelength range of 4~18μm are systematically studied,by varying the structural parameters of the gold array including the particle radius,the particle height,the particle separation,and the particle shape.The results in this work reveal a resonance characteristics within the wavelength range of 8~10μm that occurs when the incident light resonates with the induced surface plasmons of the gold micro-nano array.The results also indicate that the resonance wavelength,the absorptance peak intensity and the full width at half maximum intensity of the resonance spectrum can effectively be adjusted by tuning the structural parameters of the gold array.Based on the spectral characteristics demonstrated in this work,the proposed gold micro-nano array structure may be utilized in the future design of photoelectric sensors at the mid-infrared wavelength regime.