Electro-optic probing of gallium arsenide microwave circuits

A continuous wave laser based electro-optic probing instrument and a pulsed laser based electro-optic probing instrument were designed and constructed for electro-optic probing of circuits fabricated on gallium arsenide (GaAs).;The pulsed electro-optic probing instrument used a laser diode as the probe beam. The proposed calibration technique for removing the effects of MBR would also apply to the pulsed electro-optic probing instrument. A comparison of CW electro-optic probing with pulsed electro-optic probing measurements demonstrated the usefulness of a low frequency CW instrument for predicting problems that may occur in high frequency testing.;GaAs circuits tested with the CW electro-optic probing instrument exhibited a nonlinear dependence of the output light intensity of the instrument on the laser light intensity supplied to the electro-optic probing instrument. A thermal model based on the changes in the index of refraction of GaAs as the temperature varies is proposed to explain the nonlinearity.;The continuous wave (CW) electro-optic probing instrument had a unique advantage that permitted the average laser light intensity to be monitored without a loss in instrument sensitivity. Measurements of the electric field profiles of circuits fabricated on GaAs revealed the influence of multiple beam reflections (MBR) on electro-optic probing results. Multiple beam reflections were analyzed numerically, and a new calibration technique to remove the effects of MBR from electro-optic probing test results was proposed. The CW electro-optic probing instrument readily lends itself to a calibration technique based on monitoring the average light intensity of the probe beam and can enhance the sensitivity of electro-optic probing.