Multiple quantum well surface normal modulators for free-space optical communication links

Retro-communication by the joint use of light modulators and retro-reflecting devices has been proposed and demonstrated as a promising technique to further extend the use of free-space optical communication (FSO) to mobile communication. We have developed and demonstrated high-speed surface-normal GaAs-based and InP-based multiple quantum well electroabsorption modulators and arrays operating at different near-infrared wavelengths for FSO link applications. In this paper we report on the structure and device design issues, and trade-offs when GaAs-based or InPbased modulators are needed in the FSO links. In particular, the modulator structure properties, the device fabrication techniques and the device static and dynamic performance are investigated and compared.