Integrated isolators for opto-electro-mechanical systems and devices

The development of integrated isolators is critical to the functional integration of optics within OEM devices and systems. Bulk isolators have proven to be the most important components in many fiber optic systems due to their ability to protect light sources from back-reflected light. Such reflections are created at each component interface, inhomogeneity, or other perturbation in the path of the light. This paper reviews the operation of and current work in integrated isolators. Several methods for fabricating monolithically integrated magneto-optical isolators are discussed, including the fabrication of garnets, magnets, and cladding/buffer layers. Garnets are traditionally grown by liquid phase epitaxy (LPE) at temperatures and environments that are not friendly to semiconductors or other common substrates. More importantly, LPE requires epitaxial growth, which dictates garnet substrates and therefore hybrid integration techniques. We have used metallorganic chemical vapor deposition (MOCVD), sputtering, and metallorganic chemical liquid deposition (MOCLD) to deposit single-phase yttrium iron garnet (YIG). A variety of substrates were used, including MgO and SiO₂ which are promising buffer layer materials. The chemical, structural, and optical properties of the resulting films are discussed. We have also used a variety of sputtering techniques to integrate permanent magnet films with semiconductor processing. These magnets are sufficient for biasing the magneto-optical element. The chemical, structural and magnetic properties of these materials, as well as total integration will be discussed.