Abstract: Broadband electro-optic modulation spanning the visible-to-near-infrared range is critical for optical communication, optoelectronic signal processing, and imaging. Studies on the electro-optic coefficient and microscopic mechanism of high-electro-optic lead magnesium niobate-lead titanate (PMN-PT) transparent relaxor ferroelectric ceramics across different infrared wavelength ranges remain limited. In this work, La-doped 80PMN-20PT transparent ceramics were used to study multi-wavelength transmittance and quadratic electro-optic response. Over the wavelength range from 632.8 nm to 1550 nm, the quadratic electro-optic coefficient increased gradually with wavelength, reaching 40.4×10^-16 m²/V² at 1550 nm. Piezoresponse force microscopy results showed that local domain structures with a characteristic size of approximately 200 nm were observed, as well as submicron domains in certain local regions. The dielectric permittivity and dielectric loss spectra of both unpoled and poled samples exhibited no obvious glassy features in the low-temperature region, indicating that the local domain structure remains stable within the temperature range used for transmittance and electro-optic measurements. Frequency dispersion was observed between approximately 35 and 45 ℃, and the T_B before polarization was about 100 ℃. The sample also showed typical relaxor ferroelectric behavior under electric field, characterized by high induced polarization and low polarization hysteresis (P_max=23.8 μC/cm², P_r=5.1 μC/cm²). These results indicate that the increase in transmittance and quadratic electro-optic coefficient with wavelength is closely related to the local polar structure and its reversible low-field polar response.

Key words: PMN-PT transparent ceramic, relaxor ferroelectric, domain structure, electro-optic coefficient, visible-near-infrared spectroscopy