Electro‐birefringence from paraelectric defects in cubic crystals

Abstract

The electro-birefringence effects are discussed and produced in an (electro-optically inactive) cubio crystal by the presence of electric dipole defects which are alignable by electric fields. Based on the electronic polarizability tensor of the defects and their paraelectric alignment functions, expressions for the field-induced birefringence (Kerr or Pockels effect) can be derived for all interesting symmetries of dipoles, electric fields, and light-geometry, and their connectionsby Kramers-Kronig relationsto elect,ro-dichroism can be given. Various methods for electrobirefringence measurements with dc, ac, dc + ac, and birefringence-bias techniques producing linear, quadratic, and quartic E-dependence of the electro-optical effect are discussed. The derived behavior is illustrated by experimental examples selected from Kerr effect measurements on CNdefects in alkali halides.Die feldinduzierte Doppelbrechung in kubischen Kristallen mit elektrischen Dipol-Stdrstellen wird diskutiert. Quantitative Ausdriicke fur den Kerr-und Pockels-Effekt (basierend auf dem Polarisierbarkeitstensor und der paraelektrischen Ausrichtfunktion der SMrstellen) werden fiir alle interessierenden Dipol-, Feld-und Lichtgeometrien angegeben, mitsamt ihrer Kramers-Kronig-Beziehung zum feldinduzierten Dichroismus. Verschiedene MeBmethoden mit Gleichspannungs-, Wechselspannungs-, Gleich-und Wechselspannungs-nnd ,,Doppelbrechungs-Vorspannangs"-Technik, die lineare, quadratische und quartische Feldabhangigkeit erzeugen, werden diskutiert. Das abgeleitete Verhalten wird illustriert mit experimentellen Beispielen von Kerr-Effekt-Messungen an CN--Stdrstellen in Alkali-Halogeniden.

Kerr effect and birefringence from paraelectric CN− defects in nine alkali halides

“…For KC1: CN-, the value from a recent and very accurate calibration in our laboratory By thermal treatment in chlorine gas, the OH-content could be reduced to unmeasureable amounts (< lOI4 while the CNand CNO-content remained basically unchanged. As discussed in detail in a previous paper [15] the presence of any background birefringence in the crystal can seriously interfere with the Kerr-effect measurements. The control (and minimizing) of these background An effects was therefore essential for all field-induced An measurements.…”

“…The general principles and techniques to measure electro-birefringence under different conditions of geometry, optical or electrical bias, dc or ac application, etc., has been extensively reviewed in a preceding paper [15]. For the measurements in this work, the Kerr-effect geometry and dc field application was used exclusively.…”

Structure of the 1:1 molecular complex of durene with 1,2,4,5-tetracyanobenzene

“…Among the complexes of 1,2,4,5-tetracyanobenzene (TCNB) the most extensively studied were those with anthracene (Tsuchiya, Marumo & Saito, 1972;Stezowski, 1980;Lefebvre, Odou, Muller, Mierzejewski & Luty, 1989) and naphthalene (Kumakura, Iwasaki & Saito, 1967;Lefebvre et al, 1989). The experimental and theoretical effort devoted to the complexes of TCNB (Luty & Kuchta, 1986;Luty, 1988) allowed the workers to conclude that the presence and nature of the disorder depends on the size and symmetry of the donors embedded in the orientationally ordered TCNB sublattice. The character of the observed disorder may be dynamical (anthracene-TCNB), static (naphthalene-TCNB) or statistically static (pyrene-TCNB).…”