Identification of ferroelectric domain structure sensitive phonon modes in potassium titanyl phosphate: A fundamental study

Abstract

Confocal Raman spectroscopy is applied to identify ferroelectric domain structure sensitive phonon modes in potassium titanyl phosphate. Therefore, polarization-dependent measurements in various scattering configurations have been performed to characterize the fundamental Raman spectra of the material. The obtained spectra are discussed qualitatively based on an internal mode assignment. In the main part of this work, we have characterized z-cut periodically poled potassium titanyl phosphate in terms of polarity-and structure-sensitive phonon modes. Here, we find vibrations whose intensities are linked to the ferroelectric domain walls. We interpret this in terms of changes in the polarizability originating from strain induced by domain boundaries and the inner field distribution. Hence, a direct and 3D visualization of ferroelectric domain structures becomes possible in potassium titanyl phosphate. V

Time-domain spectroscopy of KTiOPO4 in the frequency range 06–70 THz

“…The laboratory frame is indicated by x, y, z. Following the paper by Kugel [30] we use both the Porto notation k i (e i , e s )k s , [46] and, the polarization direction, e.g. E || a for easier comparison between results from other publications.…”

Imaging of 180∘ ferroelectric domain walls in uniaxial ferroelectrics by confocal Raman spectroscopy: Unraveling the contrast mechanism

“…In this paper polarization-dependent Raman spectroscopy will be performed. To unambiguously identify the scattering geometries the Porto notation [k i (e i , e s )k s ] will be used, where the vectors k i,s denote the direction of the incident and scattered light in crystal coordinates, while e i,s references the polarization of the light with respect to the crystal axis system [8,23,35].…”

“…In the last decade, Raman microscopy has been applied to visualize and analyze ferroelectric domain structures in numerous materials [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. A relation between the phonon spectra and ferroelectric domain walls (DW) was first noted by Dierolf et al in 2004 [1] performing luminescence microscopy on periodically poled, Er-doped lithium niobate.…”

“…However, Raman spectroscopy is sensitive to other effects as well, such as crystallographic defects [7,16,22], stoichiometry [22,23], strains [24][25][26], or E fields [27]. The understanding of those effects and their interaction with domain structures is particular important in technological relevant systems, such as periodically poled waveguide structures [2,8,74]. This makes * mruesing@eng.ucsd.…”

“…We have performed systematic measurements on domain walls for all scattering configurations on zand y-cut samples in the common nonlinear materials LiNbO 3 , LiTaO 3 , and potassium titanyl phosphate (KTiOPO 4 , KTP). While most previous works have only studied domain grids in z-cut geometries [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15], we have specifically investigated domains on y-cut surfaces with Raman spectroscopy. This provides access to completely different phonon spectra.…”