Abstract

Electrooptic sampling in GaAs is a very powerful technique to evaluate ultrafast microwave circuits.¹ We present a new detection scheme for the electrooptic effect based on the modulation of the interference generated by multiple beams reflected from the front and back surfaces of the GaAs substrate. The electric field applied to the microstrip line modulates the refractive indices of GaAs and thus changes the effective optical thickness of the medium. Demodulation is performed simply by measuring the intensity of the interference light beam. There is no need for a polarizer (analyzer) in front of the photodetector; this simplifies the experimental procedure. We show that the interference effect cannot be neglected since the intensity of the first back surface reflection is comparable with that of the front surface reflection. A comparison between calculated signals for this method and for the conventional method described in Ref. ¹ shows that they have the same optimum sensitivity. This was confirmed by our experiments.

© 1989 Optical Society of America