Specific Recording Kinetics as a General Property of Unconventional Photorefractive Media

Abstract

We introduce a model for the kinetics of grating formation during holographic recording in optically excitable two-state systems. An unexpected characteristic time dependence of the diffraction efficiency is found. We show that it originates from a nonlinear transformation of the light interference pattern into a refractive-index profile. Our findings strongly resemble and explain by nature the experimental data of two-state systems in general, here represented by two examples: sodium nitroprusside and terbium gallium garnet.

Photoinduced Nitrosyl Linkage Isomers Uncover a Variety of Unconventional Photorefractive Media

“…The scattering vanished with heating above 260 K and 190 K for [Ru(NH 3 ) 5 -NO]Cl 3 · H 2 O and K 2 [Ru(NO 2 ) 4 (OH)NO], respectively. This shows already that the phenomenon of holographic scattering is connected with the nitrosyl-linkage isomer, which indeed has a decay temperature of T M = 260 K [17] and T M = 190 K [18] for the two compounds, respectively.…”

“…Here an optical bistability is at the origin of photorefraction and the kinetics show a characteristic transient behavior. [5] The unique properties of this class were com- [6][7][8] where light irradiation induces a rotation of the NO ligand by 180°in the [Fe(CN) 5 NO] 2-complexes, [9] as illustrated in y. [10][11][12][13] In all these compounds light-induced linkage isomers of the NO ligand can be accessed by a metal-to-NO chargetransfer transition.…”

“…To prove the general relation between photoinduced linkage isomers and the appearance of photorefraction, we focus on two further representatives of nitrosyl-containing complexes, namely [Ru(NH 3 ) 5 Thus we have the possibility to strictly relate any optical response to the NO-metal moiety of the compound independent of the chosen ligands and the charge of the complex.…”

“…One of the latest discovered photorefractive materials is Na 2 [Fe(CN) 5 NO] · 2H 2 O, in which metastable linkage isomers of the nitrosyl group can be generated by light irradiation resulting in huge changes of the refractive index up to Dn ∼ 10 -2 .…”

“…This remarkable transient behavior of the scattered light intensity is analogous to that found for SNP, [14] and has been successfully described on the basis of an optically bistable photosensitive material consisting of the two configurations M-NO and M-ON. [5] The scattering maximum represents the state where a spatial modulation of the number density of M-ON, that is, a spatial modulation of the refractive index change, reaches its maximum amplitude. This spatial modulation vanishes in an overexposed sample, where the number density of molecules transferred to the isonitrosyl configuration M-ON is homogenous in the whole crystal.…”