The polarization ratio of a laser can be calculated by converting the light emitted from the laser diode into parallel rays with a collimator lens and by finding the ratio of the maximum to minimum value of the quantity of light while rotating a polarized beam splitter.
The polarization ratio generally has different values, depending on the aperture diameter of the collimator lens and the optical power output of the laser diode. Therefore, it is necessary that the measurement conditions that match the operating conditions are set.