Rapid measurement method of intracavity phase retardation based on laser frequency splitting

We present a method for phase retardation measurement of intracavity optical elements which is based on frequency splitting caused by weak phase anisotropy of Nd: YAG. The measurement range covers 0-π and the measurement uncertainty is less than 0.0300 rad. A theoretical analysis is provided to obtain the phase retardation of intracavity optical elements by using the phase difference or frequency difference of two eigenmodes. The minimum error is 0.0036 rad by using the composite wave plate to verify various phase retardation conditions. This work provides a rapid and accurate intracavity method for measuring the phase retardation of optical elements.