Acceptance Mode Dependent Transfer of Non-Common Path Aberrations to Null Leakage in Mid-Infrared Nulling Interferometry

Mid-infrared nulling interferometry enables thermal characterization of warm exoplanets, but non-common path aberrations (NCPA) degrade starlight suppression by creating complex amplitude mismatch between interferometer arms. We investigate how architecture and NCPA spatial structure jointly determine null leakage and stability at λ=10.6 μm. A unified statistical framework combines free-space propagation, a Houizot chalcogenide fiber, and a Labadie-type waveguide with extended Sauvage-type NCPA screens and adaptive optics (AO) residuals in nested Monte Carlo simulations. The mean raw null is governed mainly by the combined aberration amplitude of the two arms and depends only weakly on its allocation between them. AO residuals set leakage floors that depend on the reception configuration. Cases with similar mean raw nulls can still have different dispersions. Compared with free space, the single-mode spatial filters lower the mean leakage and reduce fluctuations, and they are less sensitive to the allocation of amplitude error between the arms. Their performance depends on modal selectivity: larger energy fractions in azimuthally symmetric radial modes are associated with poorer mean nulls and greater AO-driven fluctuations. These results show that NCPA tolerances cannot be specified by global wavefront error amplitude alone. They should also account for aberration spatial content and the modal projection imposed by the transmission architecture.