SPPS

SPPs is an acronym that can refer to multiple concepts, but most commonly it denotes surface plasmon polaritons in nanophotonics. Surface plasmon polaritons are quasiparticles arising from the coupling of photons with collective electron oscillations at a metal–dielectric interface.

Excitation and properties: Because the SPP wavevector exceeds that of light in the adjacent medium, direct illumination cannot excite them; momentum matching via prism coupling (Kretschmann or Otto geometry), grating couplers, or near-field probes is required. They are highly confined to subwavelength scales, with wavelengths shortened relative to free-space light. Propagation lengths are limited by metal losses, typically ranging from a few micrometers to several tens of micrometers depending on wavelength and materials.

Applications: SPPs enable a variety of plasmonic technologies, including sensing and spectroscopy (such as label-free refractive index sensors and surface-enhanced Raman spectroscopy), plasmonic waveguides for on-chip nanophotonic circuits, and enhanced imaging or light concentration at the nanoscale. They also play a role in modifying light–matter interactions for photovoltaics and color filtering in certain devices.

Materials and challenges: Realizations commonly use noble metals such as gold or silver. Optical losses in these metals limit propagation length and efficiency, while surface roughness and fabrication imperfections can degrade confinement. Research areas include hybrid metal–dielectric structures, alternative materials with lower losses, and methods to actively control or compensate losses for practical devices.

Other uses: The acronym SPPs is also used in various fields to denote different terms, depending on context. Where this acronym appears, the intended meaning should be clarified.