| There is currently significant interest in technologies that can provide compact, low-cost optical amplifiers for metro and access networks. Vertical-cavity semiconductor optical amplifiers (VCSOAs) are a new class of devices that show promising characteristics for these applications. VCSOAs have a number of advantages over in-plane SOAs, such as high coupling efficiency to optical fiber (facilitating a low noise figure), polarization independent gain, and low power consumption due to a small active volume. The typically narrow gain bandwidth of VCSOAs makes these devices function as amplifying filters. In addition, the vertical cavity design allows for on-wafer testing and fabrication of two-dimensional arrays.; This thesis presents two generations of long-wavelength VCSOAs and a broad theoretical VCSOA model, and investigates potential VCSOA applications. The theoretical model is based on the Fabry-Perot equations for a cavity with gain, and rate equations for the carrier density and photon density. It includes an analysis of how the mirror reflectivities affect all VCSOA properties—gain, gain bandwidth, saturation, and noise figure. Two generations of optically pumped long-wavelength VCSOAs were designed, fabricated, and analyzed. Both generations were optimized for reflection mode operation and fabricated by InP-GaAs wafer bonding. The first generation was a fairly simple planar structure where the lateral dimensions of the active region were defined by the optical pump beam. The objectives of these devices were to investigate basic VCSOA properties and to validate the theoretical model. The goals of the second generation VCSOAs were to improve the efficiency and reach higher gain than what was achieved with Generation 1. The difference in the designs was the carrier confining structure in Generation 2. This resulted in significantly decreased carrier loss, and produced a threefold efficiency improvement. The results of the second generation VCSOAs are, in summary: 17 dB fiber-to-fiber gain, 6.1 dB noise figure, and −5 dBm saturated output power. Two applications, switching/modulation and optical preamplification of high-speed receivers, were investigated. Optical preamplification at 10 Gb/s was demonstrated. Using a VCSOA operated at 11 dB of gain, the sensitivity of a PIN receiver was improved by 7 dB resulting in a receiver sensitivity of −26.2 dBm. |
