Raman spectroscopy and nonlinear optical properties of PbTiO3 suspension

Ultrafine PT (lead titanate) powders were dispersed in different liquids to form uniform suspensions of ferrofluids. PT powders in ellipsoidal and needle like morphologies derived from the sol-gel process and hydrothermal synthesis were suspended in organic solvents. Nonlinear optical properties such as second harmonic generation and degenerate four-wave mixing (DFWM) and the Raman spectra were investigated. The microstructures of the powders were analyzed on the basis of the Raman spectra. Phase conjugation via DFWM was examined. Changes of optical properties under application of a bias electric field to the samples are shown. The vibration modes are shown to be different for different PT powder shapes and sizes. More vibration modes in the long wavenumber region are damped in larger needle-like PT powders. The spontaneously polarized PT powders and suspensions possess second-order and third-order nonlinearities. Needle-like PT powders are better for the control of alignment in some liquids