Stokes polarimetry-based second harmonic generation microscopy for collagen and skeletal muscle fiber characterization

Nirmal Mazumder,Fu-Jen Kao

doi:10.1007/s10103-020-03144-6

Abstract

The complete polarization state of second harmonic (SH) light was measured and characterized by collagen type I and skeletal muscle fiber using a Stokes vector-based SHG microscope. The polarization states of the SH signal are analyzed in a pixel-by-pixel manner and displayed through two dimensional (2D) Stokes vector images. Various polarization parameters are reconstructed using Stokes values to quantify the polarization properties of SH light. Also, the measurements are extended for different input polarization states to investigate the molecular structure of second harmonic generation (SHG) active molecules such as collagen type I and myosin.

Highlights

The second harmonic generation (SHG) is a second-order nonlinear coherent optical process via virtual state transitions, widely used for imaging non-centrosymmetric molecules [1, 2]
We describe the potential of Stokes vector-based SHG microscope to investigate the polarization properties of SH light from collagen type I and skeletal muscle fiber, where SH signal is generated from the C-N pair of the peptide bond in protein and synthetic oligopeptides [48]
We demonstrate the reconstruction of 2D Stokes vector and various polarization parameter images including the degree of polarization (DOP), linear polarization (DOLP), circular polarization (DOCP), and anisotropy

Summary

Introduction

The second harmonic generation (SHG) is a second-order nonlinear coherent optical process via virtual state transitions, widely used for imaging non-centrosymmetric molecules [1, 2]. It should be noted that SH intensity generated only from noncentrosymmetric molecules and depends on the orientation of SH active molecules (collagen fiber, myosin) as well as the polarization state of excitation light [27,28,29]. The SHG signal generation is strongly dependent on the angle between the input state of laser polarization and collagen alignment and the collagen orientation can be determined through the degree of polarization (DOP) [35, 36].

Results

Conclusion