Superluminal X-waves in a polariton quantum fluid

摘要

X-waves, localized wave packets that retain their shape while propagating, have been made in a polariton quantum fluid for the first time. X-waves are far less fragile than other types of localized waves such as solitons as their existence does not depend on strong nonlinearity and hence high signal powers, making them more robust against losses. Antonio Gianfrate and co-workers at Istituto di Nanotecnologia, Italy, along with collaborators in Poland demonstrated spontaneous generation of X-waves in an exciton-polariton superfluid. This superfluid was cooled to 10 kelvin in a semiconductor microcavity consisting of three quantum wells sandwiched between two distributed Bragg reflectors. Using ultrafast digital holography, the team observed how an initial Gaussian photonic pulse injected into the microcavity was reshaped into a polariton X-wave. Polariton X-waves are promising for photonic signal processing on chips.