Motional effects in retardation plates and mode locking in ring lasers

The effect of a relative velocity upsilon between source and retardation plate is to create an additional retardation, deltaphi, proportional to (nu/c) (l/lambda), where c is the velocity of light, i the plate thickness, and lambda the wavelength of the light. The effect suggests a possible solution to the problem of mode locking in ring lasers and a method, of increasing sensitivity in a Sagnac polarization ring interferometer. The effect is compared with those sought unsuccessfully by Lord Rayleigh and Brace around 1900.