Part 1
表面等离子体（surface plasmons，SPs）
是一种电磁表面波，它在表面处场强最大，在垂直 于界面方向是指数衰减场，它能够被电子也能被光 波激发。表面等离子体是目前纳米光电子学科的一 个重要的研究方向，它受到了包括物理学家，化学 家材料学家，生物学家等多个领域人士的极大的关 注。 一般来说，表面等离子体波的场分布具有以下特性： 1.其场分布在沿着界面方向是高度局域的，是一个 消逝波，且在金属中场分布比在介质中分布更集 中，一般分布深度与波长量级相同 2.在平行于表面的方向，场是可以传播的，但是由 于金属的损耗存在，所以在传播的过程中会有衰 减存在，传播距离有限。
Part 1
表面等离激元
表面等离激元( Surface Plasmon Polaritons， SPPs)是光和金属表面的自由电子相互作用所引起的一种电磁波模式，
或者说是在局域金属表面的一种自由电子和光子相互作用形成的混合激发 态。在这种相互作用中,自由电子在与其共振频率相同的光波照射下发生 集体振荡。它局限于金属与介质界面附近,沿表面传播,并能在特定纳米结 构条件下形成光场增强，这种表面电荷振荡与光波电磁场之间的相互作用 就构成了具有独特性质的SPPs。 早在一百年前,人们就认识到贵金属(合金)纳米颗粒在可见光区表现出很 强的宽带光吸收特征。这种现象实质上是由于费米能级附近导带上的自由 电子在电磁场的驱动下在金属面发生集体振荡,产生所谓局域表面等离激 元;共振状态下电磁场的能量被有效地转变为金属表面自由电子的集体振 动能。
Part 1
Surface plasmon polaritons(SPPs)
Surface plasmons (not SPPs), occur as light induced packets of electrical charges collectively oscillate at the surfaces of metals at optical frequencies. Under specific conditions, the light that radiates the object (incident light) couples with the surface plasmons to create selfsustaining, propagating electromagnetic waves known as surface plasmon polaritons (SPPs). Once launched, the SPPs ripple along the metal-dielectric interface and do not stray from this narrow path. Compared with the incident light that triggered the transformation, the SPPs can be much shorter in wavelength. In other words, when SPs couple with a photon, the resulting hybridised excitation is called a surface plasmon polariton (SPP). This SPP can propagate along the surface of a metal until energy is lost either via absorption in the metal or radiation into free-space.
p
Part 1
在金属中，价电子为整个晶体
所共有，形成所谓费米电子气。价 电子可在晶体中移动，而金属离子 则被束缚于晶格位置上，但总的电 子密度和离子密度是相同的，从整 体来说金属是电中性电子的海洋中”。这种情况和气
体放电中的等离子体相似，因此可 以把金属看作是一种电荷密度很高 的低温（室温）等离子体，而气体 放电中的等离子体是一种高温等离 子体，电荷密度比金属中的低。
表面等离激元
Surface plasmon polaritons, SPPs
李伟 2013.11.25
Contents
Part 1
Part 2
Part 3
Part 4
什么是表面 等离激元
怎么激发表面 表面等离激元 等离激元 的性质及应用
磁共振
Part 1
巴黎圣母院的玫瑰窗
Part 1
表面等离激元
表面等离子体
3.表面等离子体波的色散曲线处在光线的右侧，在
大。
相同频率的情况下，其波矢量比光波矢量要
Part 1
Surface plasmons (SPs)
Surface plasmons (SPs) are coherent electron
oscillations that exist at the interface between any two materials where the real part of the dielectric function changes sign across the interface (e.g. a metal-dielectric interface, such as a metal sheet in air). SPs have lower energy than bulk (or volume) plasmons which quantise the longitudinal electron oscillations about positive ion cores within the bulk of an electron gas (or plasma). When SPs couple with a photon, the resulting hybridised excitation is called a surface plasmon polariton (SPP). This SPP can propagate along the surface of a metal until energy is lost either via absorption in the metal or radiation into free-space. The existence of surface plasmons was first predicted in 1957 by Rufus Ritchie. In the following two decades, surface plasmons were extensively studied by many scientists, the foremost of whom were T. Turbadar in the 1950s and 1960s, and Heinz Raether, E. Kretschmann, and A. Otto in the 1960s and 1970s. Information transfer in nanoscale structures, similar to photonics, by means of surface plasmons, is referred to as plasmonics.
Part 1
表面等离激元
当光波(电磁波)入射到金属与介质分界面时，金属表面的自由 电子发生集体振荡，电磁波与金属表面自由电子耦合而形成的一种 沿着金属表面传播的近场电磁波，如果电子的振荡频率与入射光波 的频率一致就会产生共振，在共振状态下电磁场的能量被有效地转 变为金属表面自由电子的集体振动能，这时就形成的一种特殊的电 磁模式：电磁场被局限在金属表面很小的范围内并发生增强，这种 现象就被称为表面等离激元现象。 目前, SPPs已经被应用于生物、化学、传感、光电子集成器件 等多个领域。实际应用中, 只有当结构尺寸可以与SPPs传播距离相 比拟时, SPPs特性和效应才显露出来, 有时候也用表面等离子体共振 ( Surface Plasmon Resonance, SPR)技术来描述其相关特性。
Part 1
Surface plasmon polaritons(SPPs)
Surface plasmon polaritons (SPPs), are
infrared or visible frequency electromagnetic waves, which are trapped at or guided along metal-dielectric interfaces. These are shorter in wavelength than the incident light (photons). Hence, SPPs can provide a significant reduction in effective wavelength and a corresponding significant increase in spatial confinement and local field intensity. Collective charge oscillations at the boundary between an insulating dielectric medium (such as air or glass) and a metal (such as gold, silver or copper) are able to sustain the propagation of infrared or visible frequency electromagnetic waves known as surface plasmonpolaritons (SPP). SPPs are guided along metal-dielectric interfaces much in the same way light can be guided by an optical fiber, with the unique characteristic of subwavelength-scale confinement perpendicular to the interface.