Polarization Maintaining Fiber-Based Depth Encoded Cross-Polarized Optical Coherence Tomography

Abstract

Cross-polarized optical coherence tomography offers improved imaging contrast of birefringent tissue, such as collagen organization, compared to conventional optical coherence tomography systems. Therefore, it is a promising diagnostic tool for fibrosis and cancer. Existing cross-polarized optical coherence tomography systems require free-space polarization-controlling elements, which makes these systems bulky. In this work, we present a polarization-maintaining fiber-based minimalistic system for cross-polarization optical coherence tomography suitable for endoscopic applications. A long section of a polarization maintaining fiber is placed in the sample arm and acts as a delay line due to a large group-delay difference for two orthogonally polarized modes of the fiber. Co- and cross-polarized images appear at different depth positions within the image, providing a contrast enhancement due to visualization of the change of the light’s polarization state in tissue. We demonstrate system designs for both benchtop and hand-held configurations. The images of a mouse’s esophagus ex-vivo and the nailbed of a human volunteer are presented and reveal changes in the light’s polarization state due to the presence of collagen in the tissue. The proposed all-fiber-based cross-polarized optical coherence tomography system has a high potential for endoscopy and can be translated to clinical applications.

Keywords

• Biomedical optical imaging
• collagen
• cross-polarized optical coherence tomography
• endoscopic imaging
• polarization-maintaining fiber