Determining the Quadratic Electro-Optic Coefficients for Polycrystalline Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT) Using a Polarization-Independent Electro-Optical Laser Beam Steerer

• Main Authors: Abtin Ataei, Paul McManamon, Cullen Bradley, Michael Wagner, Edward Ruff
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: Applied Sciences
• Subjects: relaxor ferroelectrics; Kerr effect; beam steerer; polycrystalline PMN-PT; halfwave electric field; Fourier-transform infrared (FTIR) spectroscopy
• Online Access: https://www.mdpi.com/2076-3417/11/8/3313

A polarization-independent electro-optical (EO) laser beam steerer based on a bulk relaxor ferroelectric polycrystalline Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT) was developed in this study to steer light ranging from visible to mid-IR wavelengths. A large number of the resolvable spots was achieved with this EO steerer. A Fourier-transform infrared (FTIR) spectroscopy was employed to determine the refractive index of the polycrystalline PMN-PT over a wide range of optical wavelengths. Besides measuring the transmission of this material, the capacitance bridge analysis was used to characterize the effect of temperature on the dielectric constant of PMN-PT. The performance of the steerer over a variety of wavelengths was simulated using COMSOL Multiphysics. The deflection angle for the wavelengths of 532, 632.8, 1550, and 4500 nm was measured in the lab in terms of mrad.mm/kV at two different temperatures and compared to the simulation results. The quadratic Kerr electro-optic coefficient and the halfwave electric field were determined for those four wavelengths at two different temperatures. The results showed polycrystalline PMN-PT has a large quadratic EO coefficient for visible light, almost as large in the near IR, but drops significantly in the mid-IR. No significant temperature dependency for the EO coefficients was observed for any of those four wavelengths.