Photorefractive hologram writing with high modulation depth in photovoltaic media under different boundary conditions

Abstract

Photorefractive recording response to sinusoidal intensity pattern in photovoltaic media under different boundary conditions, namely, open-circuit, crystal-resistor-circuit, short-circuit and crystal-voltage supply-circuit, are investigated by solving steady-state Kukhtarev equations numerically. In high modulation depth m limit and when photovoltaic field becomes sufficiently large, we find that both the magnitude and imaginary part of fundamental space-charge field E 1 as a function of m may transit from superlinear increment to sublinear increment for short-circuit condition. The role of photovoltaic field in holographic storage and two-wave mixing is also discussed in comparison with an earlier experimental literature [G. Cook et al., Opt. Commun. 192 (2001) 393]. We further generalize Gu et al.’s remark on photovoltaic field and dc space-charge field, which is for small m only [C. Gu et al., J. Appl. Phys. 69 (1991) 1167], to whole range of m in the limit donor density much larger than ionized donor density that the effect of photovoltaic field cannot be cancelled or considered as an externally applied field for an arbitrary non-zero m.