Low-Noise, Wide-Bandwidth, Large-Area APDs for Free-Space Optical Links

For future satellite to ground optical links, large-area high-performance photodetectors are key components. Phase I of this SBIR program has produced an APD design that incorporates low noise, Impact Ionization Engineering (I2E) technology, patented by the University of Texas and exclusively licensed by Agility. The Phase I results are extremely promising: the completed epitaxial design has been extensively simulated, two distinct mesa fabrication processes have been designed, and a strategy for producing planar APDs has been formulated. With these tasks completed, it is possible to calculate all of the important APD performance parameters. In all cases, the APD design meets or exceeds the specifications of the original SBIR solicitation: 3 GHz bandwidth, 50% quantum efficiency, noise performance comparable to silicon APDs, and a light sensitive diameter of 200 mm. Phase II will provide the opportunity to execute the Phase I designs by building prototypes that will demonstrate the widest bandwidth and highest sensitivity of any large area APDs ever produced. Phase II will also include reliability testing in support of the goal of delivering final prototypes that meet all of the performance targets and that are ready for industrial manufacture and deployment in military and commercial networks.