Unambiguous polarimetric reconstruction in single-input polarization-sensitive OCT via spectral polarization spreading.

Polarization-sensitive optical coherence tomography (PS-OCT) systems employing a single polarized input state are widely used due to their simple system architecture and commercial availability. However, such configurations are inherently susceptible to polarization ambiguities that can lead to inaccurate polarimetric reconstruction, particularly when estimating depth-resolved birefringence. Our previous work demonstrated that these artifacts can be mitigated by illumination exhibiting spectral polarization spread (SPS), arising from polarization mode dispersion present in some imaging systems. SPS effectively provides additional polarization diversity across the source spectrum, reducing ambiguity in the measured retardance signals. In this work, we introduce a compact waveplate stack module that introduces controlled, intentional SPS in arbitrary single-input PS-OCT systems. We demonstrate the approach by integrating the module into the round-trip portion of the sample arm of a commercially available PS-OCT platform, enabling robust and unambiguous depth-resolved polarimetric reconstruction. The minimal hardware modification and simple calibration procedure allow straightforward retrofitting of existing single-input PS-OCT systems, facilitating broader adoption of reliable, depth-resolved birefringence imaging.