Enhanced Second Harmonic Generation in Ferroelectric (Zn, Mg)O Wurtzite System

Nonlinear optical properties have been used as an essential approach for laser generation and quantum computing. Second harmonic generation is one of the nonlinear optical processes that converts two photons at ω to one photon at 2ω. Materials with high conversion effects as well as tunable polarization are often utilized to maximize the conversion efficiency such as periodic polling. Previous study shows that Zn_(1-x)Mg_xO system exhibits large ferroelectricity when combining two non-ferroelectric ZnO and MgO.¹ In this work, the linear and nonlinear optical properties of Zn_0.66Mg_0.34O are studied, and we report large second harmonic response and enhanced second harmonic coefficients in the ferroelectric Zn_0.66Mg_0.34O. The <i>d</i>₃₃of Zn_0.66Mg_0.34O exhibits improved nonlinear optical properties compared with parent compounds and is nearly two times larger than the commercial nonlinear optical crystal LiNbO₃, while exhibiting a similar bandgap. The large second harmonic coefficients and switchable polarization demonstrate a promising candidate for nonlinear optical devices and frequency conversion applications.<br/><br/><b>ACKNOWLEDGMENTS</b><br/>R.Z., G.R., S.T-M, J-P. M, and V. G. were primarily supported as part of the center for 3D Ferroelectric Microelectronics (3DFeM), an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences under Award Number DE-SC002111, for the new materials development. R.Z. also received support from the NSF MRSEC Center for Nanoscale Science, DMR-2011839 for the optical characterization. J.H received support from the Air Force Office of Scientific Research Grant number FA9550-18-S-0003 for optical characterization.<br/><br/><b>REFERENCE</b><br/>1. Ferri, K. <i>et al.</i> Ferroelectrics everywhere: Ferroelectricity in magnesium substituted zinc oxide thin films. <i>Journal of Applied Physics</i> <b>130</b>, 044101 (2021).