Maxwell–Wagner effect and second harmonic generation in gradient structures

Abstract

For the first time, we have registered, studied, and modeled the Maxwell–Wagner effect in structures with a smooth gradient of charge carriers’ mobility. The Maxwell–Wagner charge, formed after applying a DC voltage to the gradient structure at room temperature, is distributed over the entire region of the gradient. The experiments were performed with slides of a soda‐lime glass subjected to sodium‐to‐potassium ion exchange, where the ions concentration gradient provides gradient of conductivity while dielectric permittivity stays the same. The electric field generated by the Maxwell–Wagner charge is concentrated in potassium‐enriched less conductive regions of the slide and is sufficiently high to induce the second order optical nonlinearity in the initially isotropic glass. The effect causes over 100‐fold increase in a second harmonic signal relative to the signal from the surface of a virgin glass. This phenomenon in graded‐concentration structures is perspective for characterizing interfacial charges, geometry of the gradient regions, and spatial distribution of electrical conductivity in micro‐ and optoelectronic semiconductor structures.