Fig. 2: Ferroelectric polarization of the LAO/KTO interface characterized by the SHG signal.
a A schematic drawing of the SHG microscope. The half-wavelength plate can be continuously rotated to measure both \({I}_{x}^{2\omega }\left(\phi \right)\) and \({I}_{y}^{2\omega }\left(\phi \right)\), where \(\phi\) is the angle between the polarization of the incident light and the KTO crystallographic \(\left[1\bar{1}0\right]\) direction. b The wavelength of the incident laser is 1064 nm, and a pronounced SHG signal peaked at 532 nm wavelength is manifested in the reflected beam from LAO/KTO(111) at T = 2 K. c The intensity of the SHG signal ISHG is proportional to P2, where P is the power of the incident laser. d ISHG persists at low temperatures. e, f \({I}_{x}^{2\omega }\left(\phi \right)\) and \({I}_{y}^{2\omega }\left(\phi \right)\) measured at 300 K, respectively. The data (open circles) are well fitted (solid curves) by the expressions based on the m polar group.
