By analyzing the interference of two plane polarized light beam,the principle of elliptic polarization measurement is deduced and the principle of measuring the phase delay of crystals using 1/4 wave plate is introduced.

The basic principle of the laser longitudinal mode splitting is introduced briefly,and the Nd∶YAG laser longitudinal mode splitting produced by placing one and two quarter-wave plates in the cavity of a Nd∶YAG laser is investigated experimentally.

Before being depolarized,the incident linearly polarized light is converted into an elliptical polarized light by a quarter-wave plate and is divided into two or.

A method to calibrate the fast axis of a quarter-wave plate by nulling the foundamental component was proposed and the calibration principle was analyzed.

A quarter wave plate (QWP) is frequently used in a pulse Nd : YAG laser resonator and its function is determined by its location and the direction of the fast axis in the resonator.

Application of amplitude tuning in surveying geologic target thickness less than 1/4 wavelength;