Optical detrapping in Potassium Tantalate Niobate crystals

Abstract

Potassium Tantalate Niobate (KTN) optical deflectors offer exceptional speed and response time, positioning them as promising tools for imaging, telecommunications, and laser machining. KTN-based deflectors rely on electrons trapped inside the crystal to generate optical deflection. Light can interact with electrons trapped inside the crystal and release them from traps, degrading the deflector performance. Apart from the total density of trapped charge after voltage application, little is known about the nature of the electron traps in KTN, including how the optical detrapping varies with wavelength. In this work, we use phase-shifting interferometry to measure the trapped charge density inside a KTN deflector while the charge is optically detrapped by excitation light of various wavelengths. This interferometric and spectroscopic technique reveals the dependence of optical detrapping on wavelength. We also measure important properties of the KTN crystal such as the Curie temperature, optical bandgap, relative permittivity, and Ta/Nb ratio. These experiments provide insights into the detrapping behavior of KTN, useful to those seeking to utilize the material for high-performance deflectors. Further studies will be needed to obtain quantitative measurements of the trap parameters in KTN.