Oscillations in ionized gases were observed by
Lewi Tonks and
Irving Langmuir in 1929. Polaritons were first considered theoretically by
Kirill Borisovich Tolpygo. They were termed light-excitons in Soviet scientific literature. That name was suggested by
Solomon Isaakovich Pekar, but the term
polariton, proposed by
John Hopfield, was adopted. Coupled states of electromagnetic waves and phonons in ionic crystals and their dispersion relation, now known as phonon polaritons, were obtained by
Kirill Tolpygo in 1950 Collective interactions were published by
David Pines and
David Bohm in 1952, and
plasmons were described in silver by
Herbert Fröhlich and H. Pelzer in 1955. R.H Ritchie predicted surface plasmons in 1957, then Ritchie and H.B. Eldridge published experiments and predictions of emitted photons from irradiated metal foils in 1962. Otto first published on surface plasmon-polaritons in 1968. Room-temperature
superfluidity of polaritons was observed in 2016 by Giovanni Lerario et al., at
CNR NANOTEC Institute of Nanotechnology, using an organic microcavity supporting stable
Frenkel exciton-polaritons at room temperature. In 2018, scientists reported the discovery of a new three-photon form of
light, which may involve polaritons and could be useful in
quantum computers. In 2024 researchers reported ultrastrong coupling of the
PEPI layer in a Fabry-Pérot microcavity consisting of two partially reflective mirrors. The PEPI layer is a two-dimensional
perovskite made of (PEA)2PbI4 (phenethylammonium
lead iodide). Placing a PEPI layer within a
Fabry-Pérot microcavity forms polaritons and allows control of exciton-exciton annihilation, increasing solar cell efficiency and ED intensity. ==Types==