We report on the measurement and characterization of polarization properties of second harmonic (SH) light from starch granule using a Stokes vector based microscopy. The four-element Stokes parameters are the most complete description of the polarization state of SH light, including any depolarization effects. Various polarization parameters, such as the degree of polarization, the degree of linear polarization, the degree of circular polarization, as well as anisotropy are extracted by implementing a pixel by pixel image analysis from the 2D reconstructed SH Stokes images of starch granule. Furthermore, we implemented the technique by varying the polarization states of excitation light and recording the resulting Stokes parameters at micro-meter depths of resolution in order to investigate the molecular structure and orientation of the samples.

The changes of the morphology during heating and the degree of crystallinity of dry and hydrated starch granules are investigated using second harmonic generation (SHG) based Stokes polarimetry. A spatial distribution of various polarization parameters, such as the degree of polarization (DOP), the degree of linear polarization (DOLP), and the degree of circular polarization (DOCP) are extracted and compared with the two dimensional second harmonic (SH) Stokes images of starch granules. The SH signal from hydrated and dry starch on heating differed significantly in DOLP and DOCP values, indicating that hydrated starch has a greater degree of ultrastructural amylopectin disorder. The detail of denaturation and the phase transition of hydrated starch demonstrate the significant influence of thermal processing.

We report on measurements and characterization of polarization properties of Second Harmonic (SH) signals using a four-channel photon counting based Stokes polarimeter from type I collagen and starch granules. In this way, the critical polarization parameters including the degree of polarization (DOP), the degree of linear polarization (DOLP), and the degree of circular polarization (DOCP), are extracted from the reconstructed Stokes vector based SH images in a pixel-by-pixel manner. The measurements are further extended to determine the molecular structure and orientation of the samples by varying the polarization states of the incident light and recording the resulting Stokes parameters of the SH signal. The combination of SHG microscopy and Stokes polarimeter hence makes a powerful tool to investigate the structural order of starch granules under water and heating environment.