Alignment Tolerance Specifications for Holographic OAM Gen- eration: Quantifying Forked-Grating Misalignment Effects

We establish the first quantitative alignment tolerance specifications for holographic generation of or- bital angular momentum (OAM) beams, addressing a critical gap between optical design and mechan- ical implementation. While previous research focused on compensating intrinsic spatial light modu- lator imperfections, we provide a rigorous quantification of extrinsic transverse misalignment effects. Computational modeling of 1%–10% misalignments, combined with Hilbert–Schmidt fidelity analysis, reveals three operational regimes: High-Fidelity (≤3%), Critical (4–5%), and Severe Degradation (>5%). The 3% threshold (approximately 475 μm for typical gratings) emerges as a critical design parameter for mounting systems and alignment stages. These quantitative guidelines are essential for transitioning OAM technologies from laboratory demonstrations to robust, field-deployable systems in optical communications and beam shaping.