title: Revealing molecular structure and orientation with Stokes vector resolved second harmonic generation microscopy.
abstract: We report on measurements and characterization of polarization properties of Second Harmonic (SH) signals using a four-channel photon counting based Stokes polarimeter. In this way, the critical polarization parameters can be obtained concurrently without the need of repeated image acquisition. 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 by varying the polarization states of the incident light and recording the resulting Stokes parameters of the SH signal. In turn this allows the molecular structure and orientation of the samples to be determined. Use of Stokes polarimetry is critical in determination of the full polarization state of light, and enables discrimination of material properties not possible with conventional crossed-polarized detection schemes. The combination of SHG microscopy and Stokes polarimeter hence makes a powerful tool to investigate the structural order of targeted specimens.
authors.affiliation: Institute of Biophotonics, National Yang-Ming University, Taipei 11221, Taiwan, ROC.
authors.forename: Nirmal
authors.initials: N
authors.lastname: Mazumder
authors.affiliation: Institute of Biophotonics, National Yang-Ming University, Taipei 11221, Taiwan, ROC.
authors.forename: Chih-Wei
authors.initials: CW
authors.lastname: Hu
authors.affiliation: Institute of Biophotonics, National Yang-Ming University, Taipei 11221, Taiwan, ROC.
authors.forename: Jianjun
authors.initials: J
authors.lastname: Qiu
authors.affiliation: Blackett Laboratory, Department of Physics, Imperial College London, Prince Consort Road, London SW7 2BZ, UK; Max Planck Institute for the Science of Light, Günther-Scharowsky-Straße 1, 91058 Erlangen, Germany.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Foreman
authors.affiliation: Ecole Polytechnique Fedérale de Lausanne (EPFL), Lausanne, Switzerland.
authors.forename: Carlos Macías
authors.initials: CM
authors.lastname: Romero
authors.affiliation: Blackett Laboratory, Department of Physics, Imperial College London, Prince Consort Road, London SW7 2BZ, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Török
authors.affiliation: Institute of Biophotonics, National Yang-Ming University, Taipei 11221, Taiwan, ROC. Electronic address: fjkao@ym.edu.tw.
authors.forename: Fu-Jen
authors.initials: FJ
authors.lastname: Kao
mesh_terms: D002138:Calibration; D003094:Collagen / Q000737:chemistry* / Q000648:ultrastructure; D003460:Crystallization; D008027:Light; D018613:Microscopy, Confocal; D008859:Microscopy, Polarization; D010710:Phosphates / Q000737:chemistry; D017680:Potassium Compounds / Q000737:chemistry; D011487:Protein Conformation; D012542:Scattering, Radiation
chemical_list: D010710:Phosphates; D017680:Potassium Compounds; D003094:Collagen; C013216:potassium phosphate
keywords: Optical scanning microscopy; Second harmonic generation; Stokes vector; Ultrafast laser