Light-induced charge transport in ${\text{LiNbO}}_3$ crystals

We develop a concept of charge transport for congruent and stoichiometric ${\text{LiNbO}}_3$ crystals, both doped and nominally pure. The concept is based on well-established experimental facts. It incorporates fragments of the known one-center and two-center models and other important elements including electronic transitions and transport channels. The model explains qualitatively the main features of the optical damage for the congruent and stoichiometric compositions within the low-to-high intensity range.

Figure 1

(Color online) Scheme of the energy levels and main electronic transitions.

Figure 2

(Color online) Correction factor $1/q$ versus the stretching index $\beta$.

Figure 3

(Color online) Critical intensity $I_c$ versus the lifetime for level 1.

Figure 4

(Color online) Migration of an electron over level 1 (gray circles) and recombination to the ground state 0 (black squares).

Figure 5

(Color online) The line of equal contributions to the photoconductivity coming from CB and level 1. Above and below this line ${\sigma }_{\text{ph}}$ is dominated by the CB and antisite defects (hopping contribution).

Figure 6

Dependence $E_{\text{pv}}\left(N_0\right)$; curves 1, 2, and 3 are plotted for $N_1=1.5$, 1.0, and $0.7\times {10}^{20}{\text{cm}}^{-3}$, respectively.

Figure 7

Dependence $E_{\text{pv}}\left(N_1\right)$ for nominally undoped crystals. Lines 1, 2, and 3 are plotted for $N_0=0.3$, 0.6, and $1.0\times {10}^{17}{\text{cm}}^{-3}$, respectively.

Figure 8

(Color online) Intensity dependence of the light-induced field. The concentrations $N_0$ and $N_1$ are given in ${\text{cm}}^{-3}$.