Pulsed measurement of high-reflectivity mirror phase retardances.

The linear phase retardances of high-reflectivity mirrors are measured by use of the progressive modification of the polarization of a light pulse propagating in a passive Fabry-Perot cavity. This method permits determination of the linear phase retardance of a mirror with a precision of better than 0.05° and a sensitivity of better than 0.1° for any angle of incidence and any wavelength in the high-reflectivity domain of the mirror. This method also leads to a precise determination of the null-phase-retardance wavelength of the mirror.