Synthesis and Characterization of Magnetic Nanoparticles to Incorporate into Silicon Waveguides to Be Used as Optical Isolators

Abstract

Integrated optical isolators will become necessary as optical networks continue to grow and the need for monolithic integration and greater functionality increases. The use of magnetic nanoparticles as Faraday rotators to achieve isolation has been widely researched and reported. Therefore, magnetic nanoparticles are of particular interest.

Magnetic γ - Fe2O3 and SnO2 nanoparticles were synthesized using the diblock copolymer reverse micelles method. The processes were shown in detail with the aid of Raman spectroscopy to reveal the iron oxide evolution. Moreover, the magnetic properties of the nanoparticles were evaluated by superconducting quantum interference device (SQUID) magnetometer. Using a low temperature annealing process, we showed that higher percentage of γ-Fe2O3 phase was produced and could be incorporated in practical devices. One practical use is to be used as Faraday rotators in an optical isolator.

The size of the nanoparticles can be changed simply by changing the loading ratio of FeCl3 or using different polymers to yield different sizes of the nanoparticles. The size and dispersion of the nanoparticles were determined using atomic force microscopy (AFM-QNM) and scanning electron microscope (SEM). With a good control in terms of size and dispersion, the magnetic γ-Fe2O3 were employed on silicon waveguides to test for optical isolation. The results showed no optical isolation from the γ-Fe2O3 nanoparticles; this is likely due to the modal phase mismatch between the cladding and the nanoparticles. With a few changes in the design of the waveguides and dropping of the nanoparticles; we can have a fully functional integrated optical isolator on silicon.