A method of testing a device under test comprising providing a beam of
light from a light source having a first wavelength. Imposing the beam of
light on a test device over a spatial region within the test device
substantially greater than the first wavelength, wherein the test device
has a first state of refraction. Imposing the beam of light on the test
device over a spatial region within the test device substantially greater
than the first wavelength, wherein the test device has a second state of
refraction. Obtaining data resulting from the interference of the first
beam and the second beam within the device under test representative of
the voltages within the region, wherein the first state of refraction is
at a first voltage potential, and wherein the second state of refraction
is at a second voltage potential different from the first voltage
potential.
