Ultrafast nonlinear optical studies of equiaxed CuNbO3 microstructures

Abstract

Diverse microstructures of monoclinic copper niobate (m-CuNbO3) were synthesized by solid-state reaction (900°C, 3–12h). FESEM data demonstrated that agglomerated clusters grew as an elongated grains which migrated to form web-shaped equiaxed structure and dissected to form individual equiaxed microstructure. With femtosecond laser excitation (800nm, 150fs), open aperture Z-scan data revealed the presence of two-photon absorption. The nonlinear refractive index (n2) toggled between positive and negative nonlinearity for different microstructures. Web-shaped equiaxed structure kindled both the nonlinear absorption (βeff=2.0×10−12m/W), nonlinear refraction (n2=3.16×10−17 m2/W) and a strong optical limiting action (onset limiting threshold of 22.24µJ/cm2).