Polarization-resolved second harmonic generation microscopy with a four-channel Stokes-polarimeter

Area of Science:

• Optics and Photonics
• Biomedical Imaging
• Materials Science

Background:

• Second Harmonic Generation (SHG) microscopy is a label-free imaging technique.
• Characterizing polarization effects in SHG provides valuable contrast and information about sample structure.
• Quantitative polarization measurements in SHG microscopy are challenging.

Purpose of the Study:

• To develop and calibrate a photon-counting Stokes-polarimeter for spatial characterization of polarization in SHG.
• To enable quantitative measurement of polarization parameters like Degree of Polarization (DOP), Degree of Linear Polarization (DOLP), Degree of Circular Polarization (DOCP), and anisotropy.
• To demonstrate the utility of the polarimeter as a contrast mechanism in SHG microscopy.

Main Methods:

• Development of a four-channel photon counting based Stokes-polarimeter.
• Implementation of a calibration technique for quantitative polarization parameter extraction.
• Acquisition of Stokes parameters from samples using the developed polarimeter.
• Application of the technique to SHG microscopy of potassium dihydrogen phosphate (KDP) micro-crystals and collagen type-I.

Main Results:

• Successful development of a photon-counting Stokes-polarimeter for SHG.
• Quantitative measurement of polarization parameters (DOP, DOLP, DOCP, anisotropy) was achieved.
• Demonstrated the polarimeter's effectiveness as a contrast mechanism in SHG microscopy.
• Characterized polarization properties of KDP micro-crystals and collagen type-I.

Conclusions:

• The developed Stokes-polarimeter provides a robust method for quantitative polarization analysis in SHG microscopy.
• This technique enhances contrast and offers new insights into the microstructural properties of materials and biological tissues.
• The polarimeter is a valuable tool for advancing label-free imaging applications.