Nonlinear and magneto-optical transmission studies on magnetic nanofluids ofnon-interacting metallic nickel nanoparticles

Abstract

Oxide free stable metallic nanofluids have the potential for various applicationssuch as in thermal management and inkjet printing apart from being a candidatesystem for fundamental studies. A stable suspension of nickel nanoparticles of ∼ 5 nm size has been realized by a modified two-step synthesis route. Structural characterizationby x-ray diffraction and transmission electron microscopy shows that the nanoparticles aremetallic and are phase pure. The nanoparticles exhibited superparamagnetic properties.The magneto-optical transmission properties of the nickel nanofluid (Ni-F) wereinvestigated by linear optical dichroism measurements. The magnetic field dependent lighttransmission studies exhibited a polarization dependent optical absorption, known asoptical dichroism, indicating that the nanoparticles suspended in the fluid arenon-interacting and superparamagnetic in nature. The nonlinear optical limiting propertiesof Ni-F under high input optical fluence were then analyzed by an open aperturez-scan technique. The Ni-F exhibits a saturable absorption at moderate laser intensitieswhile effective two-photon absorption is evident at higher intensities. The Ni-Fappears to be a unique material for various optical devices such as field modulatedgratings and optical switches which can be controlled by an external magnetic field.