Electroabsorption waveguide modulators for high performance analog fiber links

Analog fiber optic links have been shown to be useful in antenna remoting and active phased array applications. Semiconductor electroabsorption (EA) waveguide modulators can be used in these links in view of their potential for low voltage operation, large bandwidth, and monolithic integration with other components. Important considerations of an optical modulator for analog applications are RF efficiency and the spurious free dynamic range (SFDR). In our prior work we demonstrated dual-function properties of a Franz-Keldysh effect waveguide which can function as a modulator and as a detector. As an electroabsorption modulator, a fiber optic link with a -17.4 dB RF loss and a 124 dB/Hz/sup 4/5/ sub-octave SFDR is obtained with electrical biases in the 2-3 V range. As a waveguide photodetector, a 0.45 A/W fiber coupled responsivity, photocurrents up to 20 mA, and an output third-order intercept of >34.5 dBm, are achieved at -7 V. As extensions of this work, we present (a) the results on the novel bias control of the electroabsorption waveguide modulator for maximum RF efficiency based upon the behavior of the modulator photocurrent, (b) the progress in the study of high SDFR electroabsorption waveguide modulator based upon a combination of the Franz-Keldysh effect and quantum confined Stark effect.