The lateral oxidation of epitaxially grown Al<sub>x</sub>Ga<sub>1-x</sub>As layers is investigated in an open-chamber system based on a conventional horizontal tube furnace, and in a closed-chamber system. The oxidation is selective and depends on the Al content, process temperature, and process time. The process is characterized as a function of these parameters. The closed chamber system provides faster oxidation with superior control, repeatability and uniformity of the oxidation extent as compared to the open-chamber system. Based on these investigations of the oxidation reaction, we propose a unique method for realizing 3D photonic crystals in GaAs/AlGaAs-based material.
In this paper we present the modeling, design and fabrication of high-speed photonic modulators for use at high GHz, namely millimeter wave (MMW), frequencies based on the electro-optic materials, such as LiNbO<sub>3</sub>. To accurately design the traveling wave MMW modulators rigorous EM numerical tools are used to determine the propagation characteristics of both the optical and MMW waveguides. Extensive studies have been made to achieve an optimal design, which includes a close refractive index match between optical and MMW wave and a reduction of MMW propagation loss. The designed devices have been fabricated and tested with a modulation up to 135GHz.