Integrating magneto-optical garnet isolators on semiconductor substrates.

摘要

In optical communications, laser sources need to be protected from unwanted reflected light, a challenge best act by magneto-optical isolators. For integrating magneto-optical isolators with semiconductor devices, including most of these laser sources, it is necessary to develop film fabrication methods that are friendly to batch semiconductor processes. Integrated magneto-optical isolators each consist of a magnetic film layer, optical cladding layers, and a magneto-optical waveguide layer. Traditionally yttrium iron garnet (YIG) films, which are the active layers in magneto-optic isolators, have been grown by thermal deposition process, such as Liquid phase epitaxy (LPE) on garnet substrates. Such thermal processes could damage semiconductor substrates and other semiconductor devices during the deposition, and garnet substrates are difficult to integrate with semiconductor devices. In this work, YIG films were grown by low-temperature RF sputtering onto non-garnet substrates, MgO, fused quartz, and more importantly Si and InP. Two different sputtering methods were used, one involved single target sputtering and the other was multi-target sputtering with a partial pressure differential. After deposition, either post thermal annealing by a conventional tube furnace or a rapid thermal annealing (RTA) was done. To improve the optical characteristics of YIG films, Bi or Ce was substituted into the films. Next, SmCo thin magnetic films were investigated for biasing the active layer. These were grown by RF sputtering. All deposited films were characterized with Energy Dispersive X-ray Spectroscopy (EDS), and X-Ray Diffractometry (XRD), to find atomic composition and crystal structures. Vibrating Sample Magnetometry (VSM) was done for magnetic characterization. Together with integrated photonic crystal polarizer, fully integrated optical isolator can be achieved. Finally, photonic integrated circuits (PIC) and optoelectric integrated circuits (OEIC) can be realized with semiconductor integrated laser diode, fully integrated optical isolator and other integrated optical components such as modulators, amplifiers, detectors, and switches.