Hologram Self-Enhancement

Hologram self-enhancement (HSE) was discovered by Staebler and Amodei by phase recording in LiNbO$_3$ crystals [16,17]. This phenomena was observed by Shvarts, Ozols and Reinfelde [2] in As$_2$S$_3$. HSE occurs in 3-D holograms created by recording with two beams ($I_S,I_R$) up to a given diffraction efficiency, $\eta_0$ (Fig. 11a). By a subsequent illumination or dark reactions, an increase in the diffraction efficiency was observed. The HSE is described by the self-enhancement coefficient defined as:

$$\xi=\frac{\eta_{(t)}}{\eta_0}$$ (30)

Where $\eta_{(t)}$ is diffraction efficiency in time $t$ and $\eta_0$ is initial diffraction efficiency. Three different HSE phenomena were observed in As$_2$S$_3$ films (Fig. 11): (1) coherent; (2) non-coherent and (3) dark.