Phase-coded microlens array for suppressing interference-lattice modulation in highly coherent beam homogenization

Microlens-array (MLA) homogenizers imprint a periodic interference lattice on the flat-top spot when the illumination is highly coherent, degrading uniformity. We propose a phase-coded microlens array (PC-MLA) that superimposes an optimized deterministic piston step on each lenslet, breaking the constructive-interference condition among the beamlets while leaving the aperture, curvature, and focal length unchanged. The step-height matrix is optimized using simulated annealing to suppress the array-factor lattice. Because the phase coding is decoupled from the geometric mapping, the PC-MLA suppresses the interference lattice while largely preserving the beamlet-overlap condition of a dual-MLA homogenizer. The fabricated device attains a uniformity of 92.24% and a modulation depth of 3.95%, outperforming both a periodic MLA and a random MLA while maintaining a sharp square flat-top boundary in a compact, static configuration.