An apparatus and method for laser probing of a DUT at very high temporal
resolution is disclosed. The system includes a CW laser source, a beam
optics designed to point two orthogonally polarized beams at the same
location on the DUT, optical detectors for detecting the reflected beams,
collection electronics, and an oscilloscope. The beam optics defines a
common-path polarization differential probing (PDP) optics. The
common-path PDP optics divides the laser beam into two beams of
orthogonal polarization. Due to the intrinsic asymmetry of a CMOS
transistor, the interaction of the beams with the DUT result in different
phase modulation in each beam. This difference can be investigated to
study the response of the DUT to the stimulus signal.