Frequency shift of Raman modes due to an applied electric field and domain inversion in LiNbO3

Abstract

We report changes in the frequency of Raman modes in lithium niobate that are observed under the application of external applied electric fields and after domain inversion. Inspection of the Raman peaks reveals that after domain inversion, the internal field of the crystal is reduced. A comparison of the respective frequency shifts for the different Raman modes indicates that this change in the local internal field is not limited to the ferroelectric axis, but the fields orthogonal to the ferroelectric axis also change. The Raman modes also reveal that the strength of the internal field is dependent on the concentration of intrinsic defects present in the crystal.

Local probing of the interaction between intrinsic defects and ferroelectric domain walls in lithium niobate

“…18 As shown in Table II, the corresponding directions of the frequency shifts for the EðTOÞ 1 ; EðTOÞ 3 ; AðLOÞ 2 , and EðTOÞ 8 modes at the domain wall match the shifts observed in the bulk crystal which has an electric field applied anti-parallel to the ferroelectric axis. The direction of the shifts in these modes is also identical to the shifts due to the introduction of frustrated defects by forward poling.…”

“…In order to elucidate the nature of the defect reconfiguration at the domain wall, we compare the defect-related frequency shifts at the domain wall with those shifts caused by the presence of frustrated misaligned defects present after the forward poling process 17,18 and those introduced by an applied external electric field. 18 As shown in Table II, the corresponding directions of the frequency shifts for the EðTOÞ 1 ; EðTOÞ 3 ; AðLOÞ 2 , and EðTOÞ 8 modes at the domain wall match the shifts observed in the bulk crystal which has an electric field applied anti-parallel to the ferroelectric axis.…”

“…At the domain wall, the AðLOÞ 4 mode has no noticeable shift, excluding the possibility that frustrated defects play a role. From the measured response of the Raman modes in lithium niobate due to an applied electric field along the ferroelectric axis, 18 we find that the Raman shifts in the EðTOÞ 1 ; EðTOÞ 3 ; AðLOÞ 2 ; EðTOÞ 8 , and AðLOÞ 4 modes at the domain wall are identical to those observed for a externally applied electric field along the ferroelectric axis of À12 6 5, À26 6 19, À30 6 19, À16 6 4, and 20 6 33 kV/mm, respectively. Analyzing these values, we find an effective field of À12 to À13 kV/mm that is consistent within error for all the observed shift of the different Raman modes.…”

Probing Laser Induced Space Charge Fields with Rare Earth Dopants

“…Unfortunately, these defects can serve as charge donors and traps, which result in optical damage and performance instabilities limiting the use of the material in higher power applications. In order to study the underlying build-up of space charge fields in a more detailed way, we have developed spectroscopic methods to characterize intrinsic electric fields [1][2][3]. In this paper, we present our results obtained using the emission spectra of erbium ions as a probe for space charge fields that are formed under visible laser irradiation.…”

Interface and thickness dependent domain switching and stability in Mg doped lithium niobate

“…As the oscillation of ions can be affected by electric fields and corresponding electromechanical strains in the crystal lattice, the observed composition dependent Raman contrast supports the anticipated change in Mg:LN depolarization fields due to uncompensated polarization charges at the PE interface. 57 In addition, mechanically imposed strains might contribute to lattice distortions as Mg:LN and LN undergo structural changes through unit cell expansion upon proton exchange. 58,59 It is therefore evident that the introduction of PE phases does not only modify the crystal lattice locally but also leads to long range distortions of the embedding Mg:LN matrix.…”