Photorefractive hologram writing with modulation 1

The photorefractive recording process as described by Kukhtarev's material equations is investigated for large modulation depths. We find that for modulation 1 the density N(+)(D) of ionized traps at the dark sites is zero in the steady state if dark conductivity can be neglected. Therefore, in this case, it is essential to take the depletion of ionized traps into account.