High Power and Highly Linear Monolithically Integrated Distributed Balanced Photodetectors

A distributed balanced photodetector with high saturation photocurrent and excellent linearity has been experimentally demonstrated. The maximum linear direct current (dc) photocurrent of 33 mA per branch is equivalent to 66mA in single-ended photodetectors. A setup for investigating the alternating current (ac) linearity of the receiver is proposed and experimentally demonstrated. The receiver exhibits high ac linearity, even under high power operation. The bandwidth of the receiverremains unchanged when the effective dc photocurrent is varied from 1 mA to 21 mA. The distribution of photocurrents was also measured. Device length for optimum radiofrequency (RF) performance is calculated and implemented in the design. A correlation between the dark current of the photodiodes and their failure mechanism has been established. Analyzing the failure mechanism, junction diodes are found to be more suitable for high power applications.