Slow Propagation, Anomalous Absorption, and Total External Reflection of Surface Plasmon Polaritons in Nanolayer Systems

Abstract

I predict that a nanoscopic, high-permittivity layer on the surface of a plasmonic metal can cause total external reflection of surface plasmon polaritons (SPPs). Such a layer can be used as a mirror in nanoplasmonics, in particular for resonators of nanolasers and spasers and can also be used in adiabatic nanooptics. I also show that the earlier predicted slow propagating SPP modes, especially those with negative refraction, are highly damped.Surface plasmon polaritons (SPPs) are electromagnetic waves propagating at the surface of a metal or interface between metal and dielectric, see, for example, refs 1 and 2. The SPPs possess many remarkable optical properties. Their wavelength can be significantly smaller than the wavelength in vacuum, and they can propagate long distances in comparison to their wavelength, which can be used in various plasmonic devices including waveguides 3,4 and microscopes. 5 I have introduced nanoconcentration of energy due to slowing and stopping of SPPs in tapered nanoplasmonic waveguides. 6 This effect allows one to transfer energy and coherence from the far zone to the near zone without major losses. I have also proposed the adiabatic transformation of energy in other types of graded nanostructures: a two-layer system with graded dielectric permittivity and a thin dielectric layer with variable thickness over metal. 7 In this system, I have predicted slow propagation and stopping of SPPs. The dielectric layers on the metal systems have been considered earlier as lenses and toy models of black holes. 8 Later, systems consisting of a thin dielectric layer over metal were shown to possess slow SPP propagation in a wide spectral band. 9 In this Letter, I show, in particular, that in this region of the slow SPPs, the imaginary part of the wavevector becomes on the order of its real part, so the propagation is actually absent. Therefore, even for the best plasmonic metals such as silver, this effect of slow propagation cannot actually be used in most applications envisioned in ref 9. The physical cause of this phenomenon is that in the region of slow propagation the electric fields of the SPPs are concentrated in the metal, which leads to the anomalously high losses.Even more important, I predict that besides this disappointing property, there is a new, interesting effect with significant potential applications in such systems, which has been overlooked before: total external reflection of SPPs.

Are negative index materials achievable with surface plasmon waveguides? A case study of three plasmonic geometries

“…Since each excitable wavevector resides in regimes of opposite slope, these two waves will be characterized by counter-propagating phase. Note, however, that a frequency regime with double wavevector solutions exists only for insulator thicknesses smaller than a critical cutoff thickness [25].…”

“…Note that this condition on the sign of the real and imaginary components of k is both a necessary and sufficient condition for achieving negative indices in absorbing media, including plasmon-based geometries [25].…”

Characteristics of Nanoscale Modes Guided by the Total External Reflection of Surface Plasmon-Polaritons

“…또한, 혼합 모드의 크기가 작아 질수록 이득 매질인 나노막대 내부에 존재하는 모드의 에너 지 비율이 점점 줄어들어 레이저로서의 발진 효율이 더욱 감 소하게 된다 [5] . 본 논문에서는 SPP의 외부 전반사(SPP total external reflection: SPP-TER) 원리 [8,9] 를 이용하는 SPP-TER 나노도파로 구조를 제안하고자 한다. SPP-TER 이란 금속-유전체 경계면을 따라 전파하는 SPP 모드가 상대적으로 높은 유효굴절률을 갖는 또 다른 금속-유전체 경계면을 만나면 모두 반사되는 현상으 로, 유전체 만으로 된 경계면에서는 생기지 않는 SPP 모드만 의 독특한 특성이다 [8,9] .…”

Multi-color infrared sensing with superlattice quantum dot structures and absorption enhancements

“…These can concentrate light at the nanoscale level and transfer energy and coherence from the far zone to the near zone without major losses. [11] Nanostructured metallic corrugation in the form of a diffraction grating can enhance the absorption by efficiently coupling ppolarized light and surface plasmons (SPs). Grating acts as an efficient light-SP coupler by overcoming the naturally existing momentum mismatch between light photons and the surface plasmons.…”