Full-wave analysis of optically controlled semiconductor coplanar waveguides

A three-dimensional full-wave analysis is used to estimate changes of the propagation characteristics of a coplanar waveguide (CPW) on a semiconductor substrate when optically illuminated. The analysis considers diffusion, recombination-generation processes and plasma depth in GaAs semiconductors. Quantitative estimates of optically induced waveguide phase shift and loss as a function of illumination intensity are presented. It is concluded that long semiconductor substrate recombination times (e.g., >1 /spl mu/s) may be required to make these devices useful as phase shifters and attenuators with low levels of illumination, thus implying a compromise between control speed and illumination power.<>