Meaning
Spatial variations in the phase of a light beam resulting from orientation dependent delays fall into the class of optical aberrations. Polarization wavefront distortion occurs in anisotropic or stressed materials where the two orthogonal components of light travel at different speeds. It degrades the focus and contrast of optical systems.
Engineers must map these distortions to ensure the high resolution of lithography and imaging tools.
Phase Nonuniformity
Delays across the beam profile create a wave that is no longer flat. The polarization wavefront distortion is measured in fractions of a wavelength using an interferometer. If the distortion exceeds the design limit, the system cannot achieve its theoretical resolution.
Optical Aberration
Sharpness of the final image is reduced by the lack of phase coherence. In systems with polarization wavefront distortion, the light from different parts of the aperture does not arrive at the focal point at the same time. This leads to a blurring of the fine details in a production yield.
System Efficiency
Total throughput of a laser system decreases when the phase is not uniform. When polarization wavefront distortion is present, some energy is lost to scattering or unintended diffraction. Calling a design ready for production without a full phase audit leads to high rejection rates at the final assembly stage.
The error is measured against the Strehl ratio of the optical train.
