Research on frequency stabilization of laser feedback birefringence measurement system

Natural birefringent elements such as wave plates and crystals are widely used in various optical systems. During the processing and coating process, residual stress will be introduced into the common optical components, causing birefringence. The birefringence has influences on performances of whole optical systems, which needs to be measured precisely. The birefringence measurement system was constructed based on the laser feedback effect, utilizing the linear relationship between light intensity modulation curve and birefringence in polarization flipping phenomenon. The long-term stable single longitudinal mode functioning of the laser could be fulfilled by utilizing frequency stabilization technique, which improved the anti-disturbance capability of the laser and the stability of the system. The experimental results show that the measurement accuracy of the system is within 0.24, and standard derivation of multi-measurement is within 0.18. The system can work on-line with good reliability and high stability. The system has potentials to be applied to on-line measurement of micro-stress, such as stresses in aircraft canopy, automotive glass, etc.