The detrapping rate β is determined by the height of the energy barrier the trapped hole must overcome to return to the transport sites manifold. The higher this energy barrier is, the deeper the trap and the lower the detrapping rate β are.O. Ostroverkhova and K. D. Singer, J.Appl. Phys. 92, 1727 (2002), L. Kulikovski et al., Phys. Rev. B 69, 125216 (2004)

Depending on the application, either shallower or deeper traps are desired in the material. For example, for applications that require longer charge retention (such as in data storageG. Steckman et al., Opt. Comm. 185, 13 (2000), E. Mecher et al., Nature 418, 959 (2002) or 3D displaysS. Tay et al., Nature 451, 694 (2008)), deeper traps are required.

Use the slider on the right to see how the dynamics of dark decay of the space-charge field (i.e. after the recording has stopped, and the material is kept in the dark) changes with values of β (detrapping rate) from 0.1 s-1 to 2 s-1 (typical for photorefractive polymer composites). As the detrapping rate β increases, the space-charge field Esc decays faster and therefore, at high detrapping rates, long-time retention of recorded information is not possible.O. Ostroverkhova and K. D. Singer, J. Appl. Phys. 92, 1727 (2002) The reason Esc2, and not Esc, is plotted as a function of time on the figure is because diffraction efficiency measured in Four-Wave-Mixing experiments at low applied electric fields E0 is proportional to Esc2 and therefore, dynamics of Esc2 can be directly related to that of experimentally measured diffraction efficiency.

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