The Role of the Thermal Oxide in GaAs-Based Photonic Bandgap Waveguide Microcavities

Recent work on optical microcavities is concisely reviewed in this article. Optical microcavities can be fabricated using III–V compound semiconductors by introducing a large periodic refractive-index variation along the axis of GaAs waveguides. Strong optical confinement in the microcavities is achieved by oxidizing the underlying III–V material and further optimized by preferentially etching away the oxide to form an air-bridge structure. The III–V thermal oxide is obtained from the wet thermal oxidation of high Al-content AlxGa1–xAs material. The critical role of the thermal oxide in the design and fabrication of the waveguide microcavities is outlined and the characterization of the properties of the thermal oxide salient to the fabrication of the devices is described. Finally, preliminary transmission data demonstrating the successful realization of these microcavities are presented.