Gallium arsenide supports efficient 1300-nm electro-absorption waveguide modulator

Gallium arsenide supports efficient 1300-nm electro-absorption waveguide modulator

A grou¥at the University of California at San Diego (La Jolla, CA) has demonstrated what they believe is the first high-speed multiple-quantum-well (MQW) electro-absorption

waveguide modulator using a relatively thin step-graded relaxed buffer on a gallium arsenide (GaAs) substrate. The modulator was designed and characterized at 1300 nm for microwave-

signal transmission on an analog fiberoptic link and offers the potential for monolithic

integration with other optoelectronic devices on GaAs substrates.

The waveguide modulator exhibited an electro-optic slope efficiency as high as 0.56 V?1 at an optimum bias of -1.79 V with an average intensity transmission of 46%, which is as high as that obtained in other 1300-nm MQW structures on indium phosphide (InP) substrates. Its RC-limited 3-dB bandwidth was 20 GHz, with an optical saturation intensity in excess of

17 mW. The modulator structure had a lattice constant 2.5% larger than that of GaAs and was grown on a 0.7-?m-thick three-stage compositionally step-graded InzAl1?zAs relaxed buffer.