Pintasädeplasmonien

Pintasädeplasmonien, also known as surface plasmon polaritons (SPPs), are electromagnetic excitations that propagate along the surface of a metal. They arise from the collective oscillation of conduction electrons in the metal coupled to the electromagnetic field of light. This coupling leads to a hybrid mode where the photons are strongly bound to the metal-dielectric interface.

SPPs are characterized by their wavevector, which is typically larger than that of free-space light at the same frequency. This means they are evanescent in the direction perpendicular to the surface, decaying exponentially into both the metal and the adjacent dielectric medium. The propagation length of SPPs depends on the properties of the metal and the surrounding dielectric, as well as the wavelength of the light.

The excitation of SPPs usually requires a mechanism to overcome the momentum mismatch between incident light and the SPP wavevector. Common methods include using prisms in a Kretschmann or Otto configuration, or employing gratings to scatter light and increase its momentum. Once excited, SPPs can be used to create localized electromagnetic fields with enhanced intensity, which has led to numerous applications.

These applications span various fields, including sensing, where the sensitivity of SPPs to changes in the refractive index near the metal surface can be exploited for detecting minute quantities of analytes. They are also utilized in optical filters, waveguides for subwavelength light manipulation, and in surface-enhanced Raman spectroscopy (SERS) to boost the Raman signal of molecules adsorbed on the metal surface.