Multi-atom, multi-photon collective decay (superfluorescence) following EUV-FEL pumping of He

ヘリウムのEUV-FEL励起に伴う多原子,多光子,共同脱励起(超蛍光)

永園 充*; Harries, J.; 岩山 洋士*; 富樫 格*; 登野 健介*; 矢橋 牧名*; 仙波 泰徳*; 大橋 治彦*; 石川 哲也*; 繁政 英治*

Nagasono, Mitsuru*; Harries, J.; Iwayama, Hiroshi*; Togashi, Tadashi*; Tono, Kensuke*; Yabashi, Makina*; Semba, Yasunori*; Ohashi, Haruhiko*; Ishikawa, Tetsuya*; Shigemasa, Eiji*

Superfluorescence is a collective, multi-atom, multi-photon decay process which can occur when a population inversion is created in a large number of atoms with sufficient number density. We create indirectly such an inversion on the helium 3p2s transition by pumping using 53.7 nm EUV Free-electron laser (FEL) radiation at the SPring-8 Compact SASE Source (SCSS) test accelerator beamline, producing swept inversion in a 44 mm cube gas cell. Intense, highly-directional (divergence 20 mrad), linearly-polarised radiation at 501.7 nm is emitted in the direction of the incident beam. We have studied the characteristics of the emitted pulses using a streak camera and a calibrated photodiode.