Wide-band modeling of photoinduced carriers at the end of an open-ended microstrip line

This paper presents a wide-band model describing the behavior of an open-en ded microstrip line illuminated at its termination. The photoinduced carrie rs create a plasma at the end of the line, which modifies the complex diele ctric constant and, therefore, also the field configuration. The perturbati on due to the illumination is modeled by an optically controllable terminat ion load. Its analytical expression is obtained from the integration of the conductivity predicted by the plasma theory. Measurements made on devices fabricated on a silicon substrate validate the model from 0.04 to 20 GHz fo r an illumination power density of 4 mW/mm(2) at a wavelength of 685 nm, Th e validation includes the extraction of the characteristic impedance, which is a complex value because of the low resistivity wafers used (approximate to 250 Ohm.cm).