LIFETIMES OF LASER-INDUCED POPULATION-DENSITY GRATINGS IN RUBY

A spatially periodic distribution of excited electronic states is produced in ruby which is placed into the interference region of two light beams derived from a pulsed laser (wavelength 530 nm). The spatially modulated population density acts like an optical grating and is detected by diffraction of a quasi‐cw laser beam (488 nm). The lifetimes of the population density gratings are measured for ruby crystals with 0.05 to 5% Cr‐doping and compared with the fluorescence lifetimes of the R‐lines (694 nm). For the 0.05% ruby both lifetimes are nearly equal. At higher Cr‐concentrations the grating decay is considerably faster than the fluorescent decay. The grating lifetimes are independent of the grating period A = 1 to 100 μm. From this observation an upper limit of the diffusion constant for energy transfer between excited electronic states in ruby is estimated. Copyright © 1979 WILEY‐VCH Verlag GmbH & Co. KGaA