Spectral and polarization properties of the optical rectification coefficient on off-centered square core–shell nanowires

Optical rectification coefficient (ORC) in low-symmetry nanostructures enables polarization-selective THz/MIR functionality. Here we establish the spectral and polarization properties of the ORC in off-centered square core–shell nanowires using the finite difference method validated by simulations across size, offset magnitude, and direction. A universal angular rule emerges: the response is suppressed along the displacement axis (and its orthogonal) and maximized at two robust angles. Spectral resonances redshift with size and mildly blueshift with increasing offset, consistent with intersubband scaling. The magnitude grows from small to intermediate offsets, then saturates due to wave-function co-localization, while the polarization bandwidth broadens with size and offset and is broadest for oblique displacement. These knobs program optimal angles, bandwidth, and spectral window, providing concise design rules for polarization-selective THz/MIR rectifiers and detectors.