Holographic interferometric vibration measurement based on photorefractive crystal in diffusion mode

A dynamic holographic vibration measurement system based on a photorefractive crystal of BSO in diffuse mode without the need for an external electric field, which allows for simultaneous measurement of in-plane and out-of-plane high-frequency vibrations, is studied theoretically and experimentally in this work. By adjusting the polarization state of the reference beam, the system introduces a necessary additional phase shift of π/2 to achieve highly sensitive and linear demodulation of small phase-to-intensity vibration signals. Both theoretical analysis and experimental results confirm the system's practicality and safety, demonstrating its ability to accurately detect vibrations without the risks associated with high-voltage drift mode operation. Furthermore, some factors that affect measurement sensitivity were analyzed. The results of measuring in-plane and out-of-plane vibrations showcase the system's superior performance in measuring submicron magnitude vibrations at the MHz level.