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Hologram recording is studied in thermally reduced, nominally undoped lithium niobate in the time domain from 10 ns to 100 s by means of intense ns pump laser pulses (λ = 532 nm) and continuous-wave probe light (λ = 785 nm). It is shown that mixed absorption and phase gratings can be recorded within 8 ns that feature diffraction efficiencies up to 23 % with non-exponential relaxation and lifetimes in the ms-regime. The results are explained comprehensively in the frame of the optical generation of a spatial density modulation of Nb(Li)(4+/5+) antisites and the related optical features, i.e. absorption as well as index changes mutually related via the Kramers-Kronig-relation. Implications of our findings, such as the electrooptical properties of small bound Nb(Li)(4+) polarons, the optical features of Nb(Li)(4+):Nb(Nb)(4+) bipolarons, Nb(Nb)(4+) free polarons and O-hole-polarons, the impact of light polarization of pump and probe beams as well as of the polaron density are discussed.

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The helical twisting power (HTP) of a chiral guest in a chiral or achiral mesophase as host system is a chirality observation and, therefore, should be a suitable quantity for determination of the absolute configuration. Rules correlating the sign of the HTP and the absolute configuration of the guest are not known or, as sometimes proposed, do not exist at all. The sign and size of the HTP of compounds with one or more chiral centers are determined by the effects of an intramolecular and an intermolecular chirality transfer. The intramolecular chirality transfer is a well known phenomena in the development of sector or helicity rules for circular dichroism spectroscopy. Due to the strong omisotrophy of the intermolecular chirality transfer in a liquid crystal phase the development of rules for the determination of the absolute configuration from the sign of the HTP is called in question. By analysis of the HTP and the circular dichroism (CD) of mono‐ and bis‐aminoanthraquinones we now show that the development of rules in comparison to CD measurements does seem to be possible if some specialities of the anisotropic mesophases are taken into account. Chirality 9:407–423, 1997. © 1997 Wiley‐Liss, Inc.