The effect of the ferroelectric domain walls in the scanning near field optical microscopy response of periodically poled Ba₂NaNb₅O₁₅and LiNbO₃crystals

Abstract

A study of Ba(2)NaNb(5)O(15) and LiNbO(3) crystals with periodic ferroelectric domain structures using the scanning near field optical microscopy technique is reported. Optical contrast is observed in the regions of ferroelectric domain boundaries and it is analysed using beam propagation method modelling. This reveals that the optical contrast, a consequence of changes in the refractive index, is not due to variation of the waveguide-coupling efficiency, and supports the hypothesis that it is associated with the domain array, which is related to the size of the domain.

Near-Field Scanning Optical Microscopy Applied to the Study of Ferroelectric Materials

“…10b, the measured contrast (and width) is highly reduced when the domain walls get closer. The optical contrasts are thus underestimated in this case as previously reported (Han et al, 2009). …”

“…9c and 9d). Quantitatively, such a contrast is large as compared to reported values in other ferroelectric materials (CanetFerrer et al, 2006;Lamela et al, 2009;Han et al, 2009). On the other hand, it is in agreement with respect to the theoretical predictions in Ref.…”

Optical studies of ferroelectric and ferroelastic domain walls

“…Microscopy techniques are called super-resolved when they are able to overcome the diffraction limit, which can be done notably by working in the near-field regime. They are of course very appealing for the studies of domain walls, but can be very challenging both in their implementation and interpretation [142][143][144][145][146][147][148][149][150][151][152][153][154][155][156][157][158].…”

“…Near-field scanning optical microscopy (NSOM, or SNOM) has been used to image domain structures in several ferroelectrics [142][143][144][145][146][147][148][149][150][151][152][153][154], with contrast observed at domain walls in LiTaO 3 [142,150,151], LiNbO 3 [147,148], TGS [143,153], BaTiO 3 [144] and Ba 2 NaNb 5 O 15 [147]. These measurements have been performed in different modes of operation.…”

Laser-Induced Thermal Effect on Sensitivity of Scanning Near-Field Optical Microscope Probe

“…It can be used to perform various physical and chemical processes through electromagnetic, optical, or thermal sources. [6][7][8] During operation, heating of the probe is inevitable owing to laser light absorption, which may increase temperature of the probe in the apical region up to several hundred degrees. 9) The temperature gradient in the probe leads to a gradient of the refraction index which shifts the optical mode.…”