Design and Optical Characterization of Gallium Arsenide Aluminum Arsenide Material System Reflective Modulators for Mid-infrared Free Space Optical Applications Using Solid-source Molecular Beam Epitaxy

Book excerpt: With the ever-growing usage of free space optical communication implementations, new innovations are currently being made to help improve the quality of transmission of these systems. One particular method employed to help improve transmission efficiency of optical links is shifting the transmission wavelength into the mid-infrared spectrum. Studies have shown sufficient increase in atmospheric transmission at and around mid-infrared wavelengths (near 3-5 mm). In order to successfully implement such systems at these wavelengths, devices must first be designed that are capable of optical communication operation at such wavelengths. One such device common in modern free space optical systems is the reflective modulator. This device minimizes the pointing and tracking associated with establishing free space optical connections. In this dissertation, a free space optical reflective modulator is designed using Gallium Arsenide and Aluminum Arsenide (GaAs/AlAs) to operate at midinfrared transmission wavelengths. The reflective modulator consists of multiple quantum well modulator (QWM) atop of a distributed Bragg reflector (DBR). The physical device characteristics are analyzed and the device functionality evaluated using optical characterization techniques.