The study of Stark effect in zero-phonon spectra of local centers in crystals by modulation technique

Evaluation of the true electro-optic effect in some doped KCl crystals

“…The theoretical work on the basis of the shell model [13], applied to NaI and NaF, has shown that the sign of the Kerr constant is governed by the contribution from electrostriction. The experimental and theoretical work on the Kerr effect in fluorite crystals, reported by Kaplyanskii and co-workers [27], also arrives at the same conclusion. In the case of oxygen-octahedra ferroelectrics in their paraelectric phase, a rough estimate yields approximately 25% clamping effect on the quadratic polarization optic (PO) coefficient gllll and the sign of the low-frequency coefficient gi',22 is governed by the strain-optic contribution [l].…”

Optical Stark spectroscopy of solids

“…Compensation in a (n.n.n.) vacancy position in the [1 1 1] direction results in a C 3v center [57,61] and there are also O 2À compensated sites, which would be interesting subjects for Stark spectroscopy because of their generally higher oscillator strengths. When divalent RE such as Sm 2+ and Tm 2+ are substituted for Ca 2+ no charge compensation is needed and one expects a centrosymmetric site with no linear shift or splitting.…”

“…For this reason the Russian school, with Kaplyanskii, Medvedev and Skvortsov [11,12] as its principal exponents, developed the technique of Stark-modulated spectroscopy. They analyzed the changes in line shapes or moments, from which they were able to extract shifts and splittings which were often only $1% of the spectral line widths.…”

“…Table 3 summarizes Stark effect measurements on a variety of color center systems. The earliest measurements used conventional spectroscopy, but since the inhomogeneous line widths are usually much larger than the Stark shifts and splittings, Kaplyanskii and collaborators [11,12] developed the technique of Stark modulation spectroscopy to measure these small effects. Later, Macfarlane and Shelby [71] showed that color centers exhibit spectral hole burning due to population storage in metastable optical levels as well as a persistent component attributed to photoionization.…”

Thermal expansion of calcium fluoride

“…It should be noted that the best agreement of calculated values with experimental data is obtained without fittings of parameters; the compressibility was taken from (7), and the anharmonic third order parameters C. were determined by us earlier from the analysis of the deformation characteristics of the Raman scattering spectrum (8) and the quadratic Kerr effect in fluorite (9). In contrast to the Kerr effect whose value and sign in alkaline-earth fluorides a r e determined by the anharmonicity of the Coulomb interaction (9) the contribution from the latter to the components of the thermal strain tensor in the temperature range 100 to 300 K is not more pansion is due to the reduction to zero of that part in equation (1) which is proportiona…”