Radiation trapping
Many experiments in nonlinear optics are performed in media with high optical depth. One example is our research
about optical pattern formation which is done with sodium vapour excited with a laser beam tuned to the D1-line.
In this situation the fluorescence light sent out from the excited atoms can likely be reabsorbed within the cell
and excites again neighbour atoms. This process can be repeated several times and spreads excitation over the whole
vapour cell before the fluorescence can leave the atomic sample -- the light is trapped. Our research concentrates on
this effect which is called "radiation trapping" or "radiation diffusion". It is known as an important factor in
interstellar gas clouds, in the radiative zone of our sun, in gas-discharge-lamps or other atomic samples such as
vapour cells used for experiments investigating the interaction of laser light with atomic media.
We analyse some basic experiments of nonlinear optics concerning the influence of radiation trapping, i.e. self
focusing of a laser beam in a nonlinear medium and degenerate four wave mixing. We perform our experiments in sodium
vapour in a cylindrical cell with an intense dye-laser pulse.
|
|
Publications
-
G.Ankerhold, M.Schiffer, D.Mutschall, T.Scholz, and W.Lange
"Nonlinear effects of radiation trapping in ground-state-oriented sodium
vapor"
Phys.Rev.A 48,R4031(1993)
-
M.Schiffer, G.Ankerhold, E.Cruse, and W.Lange
"Role of radiation trapping in degenerate four-wave mixing experiments"
Phys.Rev.A 49,R1558(1994)
-
M.Schiffer, E.Cruse, and W.Lange
"Light shift induced spatial structures: Application to degenerate
four-wave mixing"
Phys.Rev.A 49,R3178(1994)
-
M.Schiffer, E.Cruse, and W.Lange
"Optical hyperfine pumping as nonlinear mechanism in degenerate four-wave
mixing"
Opt.Comm. 111,521(1994)
-
M.Schiffer, E.Cruse, and W.Lange
"Dynamics of phase-conjugate signals produced by a light-shift grating"
Opt.Comm. 116,143(1995)
-
T.Scholz, M.Schiffer, J.Welzel, D.Cysarz, and W.Lange
"Spatial effects of radiation trapping in an optically thick atomic
vapor excited by a laser beam"
Phys.Rev.A 53,2169(1996)
|
