Hyper‐Raman Scattering from Infrared Active Modes in Calcite Crystals

Abstract

Yu. N . POLIVANOV and R. SH. SAYAKHOV: Hyper-Raman

Manifestations of newχ(3)-nonlinear laser interactions in calcite (CaCO3) single crystals under one-micron picosecond pumping: more than two-octave spanned Stokes and anti-Stokes multi-wavelength comb and third harmonic generation via cascaded parametric lasing

“…Here, modes of (A 1g + 4E g ) symmetry are Raman active, modes of (4A 2u + 6E u ) symmetry are IR-active (among them three modes A 2u and E u are acoustic modes), and the other remaining modes (2A 1u + 3A 2g ) are optically inactive ("silent"). It should be noted that modes of A 1u , A 2u , and E u symmetry are active in hyper-Raman scattering [86][87][88]. In numerous works, including the ones quoted above, and recorded in different excitation geometries and conditions all observed lines in Raman spectra of calcite crystals were identified with high reliability.…”

“…[58,84,85]) and the temperature behaviour of the linewidth of its scattering line [54,55], the hyper-Raman scattering which allowed to investigate the "silent" vibration modes in calcite (see, e.g. [86][87][88]), etc. The primitive D 6 3d -cell of calcite (CaCO 3 ) with space group symmetry R3c-D 6 3d contains two formula units (Z = 2) that give rise to 3N = 30 zonecenter (at k = 0) vibration degrees of freedom, described by the following set of the irreducible representation [88]:…”

“…[58,84,85]) and the temperature behaviour of the linewidth of its scattering line [54,55], the hyper-Raman scattering which allowed to investigate the "silent" vibration modes in calcite (see, e.g. [86][87][88]), etc.…”

Hyper-Raman vibrational spectroscopy with circularly polarized light

“…Some of the recent experiments have involved the study of lattice vibrations, taking advantage of the different selection rules to overcome problems associated with the use of infrared or Raman spectroscopy. The hyper-Raman effect is of particular value in the analysis of Raman-forbidden vibrations [7][8][9][10]. As an example, in the work of Vogt and Rossbroich [11] the optical dispersion of SrTiO a in the far infrared, where radiation is strongly absorbed by the crystal, has successfully been measured by hyper-Raman spectroscopy in the optical region and Raman-inactive lattice vibrations have been discovered.…”