Complete Mode Spectrum Decomposition of Complex‐Structured Light by Computer‐Generated Holography

Analyzing or probing a complex‐structured light field with a simple model to obtain its mode composition sequence and phase delays among eigenmodes is challenging. Currently, there are numerous methods for calculating the weight and analyzing the amplitude of structured light eigenmodes, particularly on orbital angular momentum light field. However, the complete mode spectrum decomposition including the eigenmodes’ indexes with the intensity coefficients and relatively phase delays still needs the comprehensive solution. In this work, the diffractive optical method to extract the complete information of complex‐structured light field composed by eigenmodes superimposed state is detailly designed and proved. Through the interference between the inverse conversion of eigenmodes in the Fourier domain, complete mode spectrum can be constructed with eigenmode ordinals, amplitude weight coefficients, and relative phases. To the best of the knowledge, this marks the inaugural use of a simple computational hologram method to fully decompose the mode spectrum information, thereby obtaining more crucial intrinsic information about the intermode phases without additional efforts. This approach on analyzation and description can serve as a vital general tool for analyzing the intensity, phase, and Poynting vector field of complex‐structured light fields.