Polarization-sensitive optical coherence tomography based on speckle modulation

Polarization-sensitive optical coherence tomography (PS-OCT) provides quantifiable polarization parameters, offering enhanced material characterization and biomedical analysis. Speckle noise is an inherent noise in interferometric imaging, which will seriously degrade the imaging quality of PS-OCT. However, current noise reduction methods mainly use spatial averaging, leading to a trade-off between speckle suppression and spatial resolution. In this Letter, we constructed a speckle modulation PS-OCT (SM-PS-OCT) system. The optimization effect of the speckle modulation method on polarization measurements was analyzed by comparing the imaging results of the agar phantom and the chicken tendon. Quantitative evaluation of the mouse brain showed that the measurement precision of polarization parameters (retardation and optic axis) was improved by nearly two times. Mouse brain imaging results showed that SM-PS-OCT was able to distinguish nerve fibers by suppressing speckle noise. In addition, we found that SM-PS-OCT has a high-resolution advantage in calculating the degree of polarization uniformity (DOPU), and the introduction of the speckle modulation method can avoid the need for the spatial window required for calculating DOPU. The imaging results of gold nanorod phantoms demonstrated that SM-PS-OCT can obtain DOPU images with an accuracy comparable to that of the spatial window method without sacrificing imaging resolution. Our work demonstrated that the speckle modulation could provide a robust method for precise and reliable polarization imaging, contributing to the development of high-precision detection tools for various applications.