The BUCHI polarization interferometer
BUCHI has adapted the successful quartz polarization interferometer by using crystals with a very high refractive index. This leads to optimum resolution and a compact design maintaining the advantage of insensitivity to mechanical disturbances.
The reason for the superior performance of this interferometer in rough environments is the difference of spatial movements and the optical path shifts for the two light beams in a birefringent crystal of variable thickness. Whereas in a Michelson type interferometer mechanical distortions directly affect the interference, such effects are reduced by a factor of 10 to 20 in a crystal interferometer.