摘要
金属纳米颗粒低聚体不仅具有等离激元共振效应实现光场亚波长范围内的局域化和增强,还可以通过泄漏光场相互干涉实现法诺共振和连续态中的束缚态,从而使得电磁场更强的局域和增强.本文采用金纳米低聚体超构表面作为石墨烯/硅近红外探测器的天线,实现了光响应度2倍的增强;通过调节纳米金属低聚体间夹角,发现当该夹角为40°时,光电流达到最大值,对应法诺共振最大的透射率,此时天线不仅汇聚光场能量还定向发射给探测器;当该夹角为20°时,光电流出现一个低谷,此时能量局域于低聚体内,金属损耗减弱了等离激元增强效果.该工作通过时域有限差分法仿真和实验相结合研究了低聚体超构表面光电耦合效率的动态过程,为提高光电探测效率提供了一种重要的途径.
Infrared imaging chips are crucial for a broad range of military,medicine and biology applications.Although silicon detectors’on-chip integration technology is matured,their low absorption in near-infrared light results in poor infrared photocurrent response.To increase the photodetector absorption efficiency,antenna-like metal nanoparticles have been widely adopted due to their plasmon resonance effects.Oligomer nanoparticles,including quaternary nanoparticles,exhibit plasmon resonance effects that localize and enhance the light field in a sub-wavelength range.Furthermore,they can interfere with each other to achieve Fano resonance and bound state in continuity,resulting in a stronger localization and enhancement of the electromagnetic field.In this study an array of gold quaternary nanoparticle oligomers is used as the antenna for a graphene/SOI(with 1μm silicon)heterojunction near-infrared detector.Each oligomer consists of four gold squares,each with a size of 250 nm,forming two pairs of dipoles similar to the orbital hybridization of hydrogen atoms.This thus results in a multi-body coupling structure with bonding state and anti-bonding state.The antenna array parameters,such as the periodic constant,gap between nanoparticles,and angle(θ)between the oligomers,are meticulously adjusted.The optimized device is characterized by using photocurrent and photocurrent mapping,achieving a 2-fold enhancement in photoresponsivity with the maximum value atθ~40°.Notably,a consistent dip in photocurrents is observed for different periods or gap arrays when the angle theta is 20°.The simulation is conducted by using finite-difference time-domain(FDTD),revealing the emergence of Fano-like resonance in the transmittance spectra of the array at approximately 850 nm.The interference caused by the strongly coupling system to the plane coupled leakage field and the nanoparticle plasmon mode results in the formation of a new discrete leakage mode,i.e.the Fano-like resonance.The antenna helps to concentrate and emit the ligh
作者
张逸飞
刘媛
梅家栋
王军转
王肖沐
施毅
Zhang Yi-Fei;Liu Yuan;Mei Jia-Dong;Wang Jun-Zhuan;Wang Xiao-Mu;Shi Yi(School of Electronic Science and Engineering,Nanjing University,Nanjing 210046,China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2024年第6期201-208,共8页
Acta Physica Sinica
基金
国家自然科学基金(批准号:61974064,61934004)资助的课题。
