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Superradiance and matter-wave amplification in a Bose-Einstein condensate. The figure shows the velocity distribution of the atoms after a condensate (highest peak at the back of each image) was illuminated by laser light. Normal light scattering (rear image) is random, and the velocity distribution was smeared out in the direction of the incident light. In contrast, collective "superradiant" scattering created several highly directional "atom laser" beams (front image).
Observation of superradiant Rayleigh scattering. (A) A cigar-shaped condensate is illuminated with a single off-resonant laser beam. Collective scattering leads to photons scattered predominantly along the axial direction, and atoms at 45 degrees. (B-G). Absorption images after 20 ms time-of-flight show the atomic momentum distribution after exposure of the atoms to a laser pulse of variable duration. When the polarization is parallel to the long axis, superradiance is suppressed, and normal Rayleigh scattering was observed (B-D). For perpendicular polarization, directional superradiant scattering of atoms was observed (E-G), and evolved to multiple-order scattering for longer laser pulses (F,G). The pulse durations are 25 microseconds (B), 100 microseconds (C,D), 35 microseconds (E), 75 microseconds (F), 100 microseconds (G). The field of view of each image is 2.8 x 3.3 mm. The scattering angle appears to be larger than 45 degrees due to the angle of observation. All images use the same color scale except for (D), which enhances the small signal of Rayleigh scattered atoms in (C).
