New Methods for Retrieving Coherence Properties of Complex Optical Fields from Intensity Measurements
Researchers have developed two new computational methods — a Tensor Gerchberg-Saxton algorithm and a Monte Carlo variant — capable of reconstructing the spatial coherence function of partially coherent light using only near- and far-field intensity measurements. The work extends the classic Gerchberg-Saxton phase retrieval framework to handle the full mutual intensity, a four-dimensional quantity describing how light waves correlate across space. Accurate coherence characterization is critical for applications such as high-power laser beam combining and quantum optical systems.
A team of researchers has introduced a new computational paradigm for retrieving both phase and coherence information from partially coherent optical fields, requiring only intensity measurements in the near and far fields. The approach generalizes the well-known Gerchberg-Saxton iterative algorithm to reconstruct the first-order spatial coherence function, formally known as the mutual intensity. Two complementary methods are presented: a four-dimensional Tensor GS algorithm that directly reconstructs the mutual intensity with high accuracy, and a Monte Carlo GS variant that trades some accuracy for substantially reduced computational cost. Both methods were validated in simulation on linear and ring laser arrays of up to 600 beams with prescribed Gaussian-decaying coherence profiles. Experimentally, the Tensor GS method was applied to a triangular array of 130 coupled lasers exhibiting inhomogeneous spatial coherence, yielding good agreement with theoretical predictions and a root mean square phase error as low as 2π/250. The work addresses a significant measurement challenge in coherent beam combining and other fields where full characterization of partially coherent light is needed without interferometric access.
What's missing
The paper does not report computational runtimes or hardware requirements for the Tensor GS method at scale, leaving open questions about practical feasibility for real-time or very large array applications. The experimental validation is limited to a single array geometry (triangular, 130 beams), so generalizability to other configurations remains to be demonstrated.
What different sources said
- arXiv physicsCenter
Phase and coherence retrieval from near- and far-field intensities
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