Resolution of electro-optic spatial phase modulators: Measurement techniques

A method is proposed for characterizing the spatial phase resolution of electro-optic materials. The resolution of these materials is an important factor in determining whether or not they are useful for making spatial phase modulators. The technique is based on a skewed Michelson or Mach-Zehnder interferometer which converts the phase measurement into a distance measurement. A simple device is constructed from a crystal of lithium niobate and the material resolution is measured. Experimental and theoretical results for the induced phase retardation and the components of the internal electric field, compare favorably.