Phonon modes of monoclinic BiB₃O₆

Abstract

IntroductionBismuth triborate, BiB 3 O 6 , a polar, non-ferroelectric crystal has attracted interest in the last years due to its outstanding nonlinear optical properties [1][2][3]. The large optical nonlinearities open up a rich field of applications for frequency conversion of laser light via χ (2) -and χ (3) -processes, e.g. phase-matched second harmonic-generation (SHG) or optical parametric oscillation (OPO) and stimulated Raman scattering (SRS).The exceptional optical non-linearities of BiB 3 O 6 have been attributed to the bonds of the [BO 3 ] units and to a lone-pair electron at the Bi ion [4]. Detailed studies of the lattice dynamics are required for a quantitative description of these bonds. Infrared (IR) and Raman studies of the phonons are so far only available at room temperature [3,[5][6][7][8]. In particular, there is no polarization-dependent infrared study, but a polarization analysis is essential for an accurate determination of the phonon frequencies in monoclinic crystals [9]. In this letter we present a detailed investigation of the linear optical response of BiB 3 O 6 in the phonon range for different polarizations at T = 20 K and 300 K. The data are analyzed in terms of a generalized Drude-Lorentz model, which allows us to obtain the frequency, the damping, the strength and the orientation of the dipole moment of each phonon mode.

Infrared-active phonon modes in monoclinic multiferroicMnWO4

“…In the case of a weak mode, φ Im (ω 0,i ) may be dominated by a stronger mode which is close in energy, and thus θ i and φ Im (ω 0,i ) may differ significantly from each other. 55…”

Femtosecond nonlinear frequency conversion based on BiB3O6

“…Several studies were devoted to the vibrational spectra of BIBO: Raman scattering [84,[97][98][99][100], IR spectroscopy [99], and polarized reflectivity measurements [101]. Stimulated Raman scattering has also been observed [98].…”

London Dispersion Effects on the Structure and Properties of Nonlinear Optical BiB3O6 Crystal

“…13 of the remaining 27 modes belong to the symmetric A1 and 14 of them belong to the asymmetric B1 symmetry and due to the lack of inversion center in BiBO both A1 and B1 modes are infrared (IR) and Raman active. [55] With the fully optimized structure (Bi2-D3/4), the vibrational modes of BiBO crystal were calculated with the CRYSATL23 package by diagonalizing the mass-weighted Hessian matrix H ij = ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi m a m b p with H ij ¼ @ 2 E=@x i @x j . [47] The calculated results (Table 4) show excellent agreement with the experimental ones, outperform a previous one [38] with the earlier version of the same package without considering the LD effect.…”

“…From Table 4, one may find there are still some unacceptable disagreement on individual modes in one or the other experimental configurations (e. g. 140 cm À 1 ), especially those at high frequencies (above 1000 cm À 1 ). [55][56][57][58] They are likely because of the confusion of the experimental assignments of the vibrational modes with mode leakage and/or isotope effect, and the low symmetry nature of BiBO makes it even worse. Therefore, the present calculated vibrational spectra may serve as a reference for experimental assignments of the observed vibrational peaks in different geometry setups for the IR or Raman spectroscopies.…”