Optic axis determination by fibre-based polarization-sensitive swept-source optical coherence tomography.
We describe a fibre-based variable-incidence angle (VIA) polarization-sensitive swept-source optical coherence tomography (PS-SS-OCT) system to determine the 3D optical axis of birefringent biological tissues. Single-plane VIA-PS-OCT is also explored which requires measurement of the absolute fast-axis orientation. A state-of-the-art PS-SS-OCT system with some improvements both in hardware and software was used to determine the apparent optical birefringence of equine tendon for a number of different illumination directions. Polar and azimuthal angles of cut equine tendon were produced by the VIA method and compared with the nominal values. A quarter waveplate (QWP) and equine tendon were used as test targets to validate the fast-axis measurements using the system. Polar and azimuthal angles of cut equine tendon broadly agreed with the expected values within about 8% of the nominal values. A theoretical and experimental analysis of the effect of the sample arm fibre on determination of optical axis orientation using a proposed definition based on the orientation of the eigenpolarization ellipse experimentally confirms that this algorithm only works correctly for special settings of the sample arm fibre. A proposed algorithm based on the angle between Stokes vectors on the Poincaré sphere is confirmed to work for all settings of the sample arm fibre. A calibration procedure is proposed to remove the sign ambiguity of the measured orientation and was confirmed experimentally by using the QWP.
Department of Materials Science and Engineering, The Kroto Research Institute, University of Sheffield, Sheffield, UK. z.lu@sheffield.ac.uk
Zenghai
Z
Lu
Deepa K
DK
Kasaragod
Stephen J
SJ
Matcher
D000818:Animals; D003094:Collagen / Q000737:chemistry; D055620:Optical Phenomena; D041623:Tomography, Optical Coherence / Q000295:instrumentation / Q000379:methods*
D003094:Collagen