Asymmetric Angular Domain Interferometry (AADI): Rotational Asymmetric Pupil-Plane Modulation for Coherent Phase Perturbation Metrology

We introduce Asymmetric Angular Domain Interferometry (AADI), a coherent optical metrology framework employing rotational asymmetric pupil-plane modulation to extract weak angular perturbation signatures from complex interference fields. The system uses a rotating half-aperture diffraction grating to intentionally break spatial symmetry within the pupil function, converting otherwise weak or spatially diffuse coherent perturbations into structured rotational signatures measurable as a differential interference signal ΔI(x,θ). The framework is particularly applicable to semiconductor nano-metrology, coherent defect inspection, adaptive optics wavefront analysis, and degraded-environment coherent sensing, where small perturbations to the angular field distribution must be detected against high-background coherent interference. AADI requires no exotic optical sources or detectors and is compatible with standard coherent imaging architectures. Numerical simulation confirms that the differential signal ΔI(x,θ) is detectable at a signal-to-noise ratio of 852, with detection threshold reached at fewer than 10,000 photons per pixel, constituting a theoretical proof of concept across all target application domains. This paper builds on the foundational occlusion interferometry framework established in Downes (2026) and is intended to motivate experimental, computational, and commercial investigation of the AADI mechanism.