Anisotropic Thermal Expansion Tensor Resolution in Sapphire Laser Substrates
Anisotropic thermal expansion in sapphire laser substrates requires precise c-axis orientation alignment to eliminate astigmatic lensing and strain birefringence.
Fizeau Interferometry
Meaning
Optical metrology uses the interference of light waves to measure the flatness and spherical accuracy of surfaces. The technique of Fizeau interferometry relies on a reference flat and an incoming laser beam to create a map of height variations. It is the industry standard for verifying the quality of precision mirrors and lenses.
Wavefront Analysis
Interference fringes appear as dark and light bands that indicate the distance between the part under test and the reference glass. In Fizeau interferometry, the shape of these bands reveals errors in the surface figure with nanometer precision. A computer converts these patterns into a three dimensional plot of the surface.
Surface Accuracy
Measurement of the peak to valley difference allows technicians to certify that a part meets its design specification. Fizeau interferometry provides a production yield metric by identifying which parts require further polishing. This process is a readiness check that must be passed before a component is integrated into a larger assembly.
Measurement Boundary
Accuracy is limited by the quality of the reference flat and the stability of the air in the test path. Because Fizeau interferometry is sensitive to vibrations and temperature changes, it must be performed in a controlled environment. The demonstrated rate of measurement depends on the isolation of the optical bench from the factory floor.