Multi-Voltage Phase Retrieval Technique Based on Weak-Light Photorefractive Effect

In high-power laser systems, the main reason of laser damage is that the phase defect of the optical element induces the modulation of the downstream light field. Accurate detection and evaluation of phase defects can improve the load capacity of laser devices. The phase retrieval technology based on multi-plane iteration has been used for the precise detection of phase defects, but the accuracy and convergence speed are limited due to the axial mechanical displacement error and the lateral alignment error of multiple images. In this paper, a multi-voltage phase retrieval method based on weak-light photorefractive effect is proposed. The equivalent nonlinear refractive index of photorefractive crystal is changed by loading different voltages in the direction of crystal axis, so as to obtain the diffraction images of samples after passing through optical systems with different degrees of nonlinearity. A nonlinear phase retrieval algorithm is developed to reconstruct phase information from the above multiple diffraction images. The experimental results show that this method can distinguish the details of the phase resolution plate of 13.92µm, the phase accuracy error is 6.67 %, and the convergence speed is better than the traditional multi-plane phase recovery method, which verifies its high-precision phase reconstruction ability under nonlinear conditions. This method can obtain multiple diffraction images by only changing the voltage without mechanical displacement, which can avoid mechanical displacement error and image alignment error to improve accuracy and convergence speed. The work of this paper provides a new dimension for the optimization of the convergence speed of phase retrieval, and extends the phase retrieval technology from the linear field to the nonlinear field, which has a certain significance for the development of nonlinear computational imaging technology.