Plasmonics for Light Trapping

A SPP is confined to the interface between the positive and the negative permittivity part and is evanescent away from the interface. SPPs can be propagating along the interface, or they can be nonpropagating, i.e., spatially confined to, e.g., a plasmonic nanoparticle (localized surface plasmons polaritons) [243]. 

Plasmonic nanocomposites can be ordered on ID, 2D, or 3D level. They can be periodic, quasiperiodic [296], aperiodic [224], or random [204]. The building blocks of these functions themselves may have different shapes, from simple to complex and from regular to irregular [297], Fig. 2.59. 

An important disadvantage of SPPs is their resonant nature, which causes a narrow bandwidth of operation. Another one is related to large absorption losses. 

The relative dielectric permittivity of plasmonic materials is negative below plasma frequency, and its dispersion is by Drude electron resonance model [298] 

Elimination of absorption losses that are obviously undesired in photodetection is a field of active investigation, and different schemes were proposed for its avoidance [299]. One of the approaches is the use of alternative plasmonic materials [300] including graphene [301]. 

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