Nonlinear optical properties of lead-free ferroelectric nanostructured perovskite

Lead-free perovskite materials with superior physical properties are currently explored for ferroelectric and optoelectronic applications. Ferroelectric materials that have large spontaneous polarization concomitantly possess large nonlinear optical response which is highly suitable for novel photonic applications. Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) is one such novel lead-free ferroelectric material with large piezoelectric response arising from existence of morphotropic phase boundary. Conventional sol–gel technique was adopted for synthesizing nanostructured BCZT (nano-BCZT) powder using citrate precursor route. X-ray powder diffraction confirmed the phase purity and high-resolution transmission electron microscopy (HRTEM) proved that the as-synthesized BCZT was indeed nanostructured. Supportively, Raman vibrational analysis was employed to validate the site occupancies of dopants and structural correlations when compared to undoped and pristine barium titanate. Nanostructured barium titanate is extensively studied as biomarkers in second harmonic generation (SHG) microscopy for bio-medical applications. In our current work, we have explored both second- and third-order nonlinear optical response of nano-BCZT. These were found to exhibit stronger SHG signal than potassium di-hydrogen phosphate (KDP) which is a well-known SHG standard. Subsequently, we also have investigated their third-order nonlinear optical properties using open aperture Z-scan technique at 532-nm excitation wavelength in the nanosecond regime. Nano-BCZT was found to exhibit strong two-photon absorption behavior. Such materials with multiphoton absorption behavior are favorable for nonlinear photonics devices such as optical limiters and contrast agents in nonlinear optical microscopy.