High-Optical-Power, Wideband Distributed Photodetectors for Optical RF Interconnects

摘要

We present the results of our Phase I Small Business Innovative Research program to investigate the feasibility of a Schottky-diode based Velocity Matched Distributed Photodetector (VMDP). The goal of the two-phase program is to define a process for designing and fabricating VMDP that achieve >60 GHz bandwidth, >100 mA current handling, and >50 % efficiency. In this program we designed and fabricated the first devices of this kind. The bandwidth of these first devices was limited to 22 GHz by excessive ohmic resistance. We believe that 100 GHz can be achieved through improved photodiode design. The responsivity of the devices was 0.05 A/W limited by poor wafer cleaves and fiber coupling efficiency. Fiber coupling efficiency can be increased through improved waveguide design. A significant output of this program is a method for designing VMDP structures that do not require back-termination. Elimination of the termination resistance doubles efficiency and improves the noise figure. SPICE models were developed to aid in rapid analysis of future designs. We conclude that through improved optical waveguide design and fabrication, it will be feasible to develop devices that meet our original targets.