A polariton is a quasiparticle resulting from the strong coupling between photons (light particles) and certain types of excitations in a material, such as electronic excitations (electrons and holes) or vibrational excitations (phonons). The interaction between light and matter in a medium gives rise to a new hybrid state known as a polariton, which exhibits properties that are distinct from those of the individual photons and excitations.
There are different types of polaritons based on the nature of the material excitations involved:
Optical polariton: This type of polariton arises from the strong coupling between photons and electronic excitations (typically excitons) in a semiconductor or other materials with electronic degrees of freedom. It results in a mixed state with characteristics of both light and electronic excitations.
Polariton in bose-einstein condensates (BECs): In certain systems, particularly in ultra-cold gases, photons can strongly couple with collective excitations of the gas, leading to the formation of a new quasiparticle called a polariton. This is different from the electronic excitations seen in solid-state physics.
Surface plasmon polariton: In the context of plasmonics, where the collective oscillation of electrons (plasmons) occurs at the interface between a metal and a dielectric, a surface plasmon polariton can form. This polariton results from the strong coupling between the surface plasmon and photons.
Polaritons have unique properties, such as the ability to carry both light and matter components, and they are of interest in the field of optics and photonics. The study of polaritons can lead to the development of new technologies, such as polaritonic devices and the exploration of phenomena like Bose-Einstein condensation of polaritons.