Method for measuring the intensity distribution of a small beam spot with phase retrieval

• A method for measuring the intensity distribution of a small beam spot is presented.
• The method overcomes many drawbacks which exist in most of the current technologies.
• This method is suitable for applications where direct measurements can be challenging.
• A simple model is established and the feasibility of the proposed approach is demonstrated.
• Based on the trend that RMS error decreases, the method is proved effective.

A method for measuring the intensity distribution of a small beam spot is presented. The proposed method involves several processes. First, an iterative phase retrieval algorithm is employed to calculate the phase distribution from two known intensity distributions at the out-of-focus distance. Then, based on the obtained phase distribution, the intensity distribution near the small beam spot is computed via the Fresnel-like transform. Finally, by comparing the obtained intensity with the known intensity near the small beam spot, we can determine the accuracy of our results. A simple model is established and the feasibility of the proposed approach is demonstrated.