Forward and backward photon echos in gases and solids

THOMAS W. MOSSBERG, Ravinder Kachru, Sven R. Hartmann

N. W. Carlson, Arjun G. Yodh, THOMAS W. MOSSBERG

Masayuki Fujita, 修治 浅香, Hiroki Nakatsuka +1 more

Backward generation of echoes with three-pulse excitation is discussed in solid and gaseous systems. The backward echo in gases is possible as in solids but with different combinations of incident pulse directions. The first experiments in a gas were performed on the atomic sodium D 1 line in both the nanosecond and the picosecond region. Furthermore, we have observed the first backward echo in a molecular system, that is, in both of the X Σ -A Σ and X Σ -B I I transitions of Na 2 . Decays of the echoes were measured as a function of buffer gas (Ar) pressure, and collisional cross sections due to phase interrupting collisions were evaluated for each of the above cases.

C. V. Heer

Richard Bausch, P Borgs, Reiner Kree +1 more

Recent experiments on superfluorescence from O 2 - centres in KCl host crystals, with quasi-one-dimensional active volumes, have shown identically shaped and perfectly synchronized forward and backward pulses in each run. This is in blatant contrast to previous experiments on atomic beams and gases in which no forward-backward correlation beyond energy conservation had been found. We argue that a linear coupling due to backscattering from the bulk or the surface of the active volume, a phenomenon much weaker in gases than in solids, is responsible for the effect.