Optoelectronics for Optically Controlled Phased-Array Systems

This work is concerned with removing some of the major obstacles in practical application of fiber -optic techniques to microwave systems. Specifically, the problems addressed are that of RF throughput and Noise Figure of a microwave fiber-optic link. Due to the nature of the link and the characteristics of the optoelectronic devices, the RF throughput and Noise Figure of existing fiber-optic links are anywhere between unsatisfactory and unacceptable. Much of this originates from the intrinsic modulation efficiency of the optical source. It may be thought that this limitation is fundamental, since the devices in question already are approaching 100 quantum efficiency. Indeed, without new technological breakthroughs this problem may well be intractable. This report describes such a breakthrough, using a newly discovered effect in quantum well lasers known as gain-lever effect. Laser diodes constructed with gain-level incorporated into its structure shows efficiency enhancement of well over 40dB, in addition to the fact that its intensity noise is actually reduced. Combining these two factors, and with proper impedance matching, it is shown that it is possible to construct a passive microwave fiber-optic link defined as one without active electrical or optical amplification exhibiting a RF throughput gain of up to 50dB and a noise figure approaching 0dB. Author