Shared-Optics Dual-Port Interferometer for Simultaneous Displacement and Angular Motion Measurement

Conventional dual-beam interferometers typically provide a single interferometric phase observable, while simultaneous measurement of displacement and angular motion may require an additional optical path or auxiliary sensor. In this work, we develop a shared-optics dual-port interferometer for simultaneous displacement and angular-motion measurement without a substantial increase in optical complexity. The proposed configuration integrates two Michelson-like interferometers in a nearly common-path shared-optics architecture, using polarization-based routing to share key optical components while providing two independent phase readouts. Under a 120nm axial displacement at 70Hz, the two phase readouts exhibited closely matched responses and broadband phase levels at the 10-4rad/Hz level, while their difference reduced the shared displacement component to below 0.3% of the individual-channel response. In the simultaneous pitch and yaw excitation at 100 and 70Hz, the pitch- and yaw-driven responses were separated in the common and differential phase signals, while weak sum- and difference-frequency components associated with nonlinear and cross-axis actuator coupling were resolved at the 10-3rad/Hz level. These results demonstrate that the shared-optics architecture can extend a compact dual-beam interferometer from differential phase sensing to simultaneous displacement and angular-motion measurement, while retaining sufficient phase resolution to identify weak cross-axis actuator responses.