Amplitude‐Weighting Synthesis for Narrowing the Main‐Ring Width of Orbital Angular Momentum Beams

ABSTRACT

A radial amplitude‐weighting method is proposed for narrowing the main‐ring width of orbital‐angular‐momentum (OAM) beams. By adjusting the radial amplitude weights over the aperture, the receiving‐plane radial field distribution is reshaped while the helical phase of the vortex beam is preserved, thereby narrowing the main ring. The synthesis objective and constraints of the amplitude weighting are first formulated. Numerical syntheses with different radial‐layer numbers are then performed to reveal the consistent weighting behavior for main‐ring narrowing and to construct a reusable radial weighting template. Representative unconstrained and sidelobe‐level (SLL)‐constrained designs are finally verified through full‐wave simulations. The results show that amplitude weighting for main‐ring narrowing generally exhibits an inner‐region‐suppressed and outer‐rim‐enhanced distribution. The proposed method effectively narrows the main ring under both unconstrained and SLL‐constrained conditions while preserving the target OAM mode.