The use of piezo-optical polarization modulation is proposed for stress analysis problems in two and three dimensions. A Stokes-meter and a new fast scattered-light technique are described. The piezo-optical effect can be advantageously used as very-small-stress sensor, when coupled with an appropriate polarimeter. In this paper, we present the theory of a polarimeter working without retardation plates, thus pro-viding low drift and accuracy. The measuring time can be as short as one millisecond. The details of realization and some performance characteristics are given. A three-dimensional stress-analysis technique is described in which the piezo-optical effect is used for polarization modulation. This method has been used successfully to measure the Mueller matrix associated with an elementary volume of a flow-birefringent liquid, thus yielding quantitative information about the velocity-gradient tensor. As another application of the piezo-optical ef-fect, we propose and describe a gravitational-wave antenna, exhibiting potentially high detectivity with a higher sensitivity than other antennas.