| Summary: | 碩士 === 國立陽明大學 === 生醫光電研究所 === 102 === We have successfully developed a unique polarimeter that is based on four-channel detection and Stokes vectors and characterized the polarization states of fluorescence and second harmonic generation (SHG) accordingly. A mode-locked femtosecond Ti: sapphire oscillator is used to for nonlinear optical excitation. Polarized light can be described by Jones calculus and Stokes vectors. However, Jones calculus is only applicable to fully polarized light, whereas Stokes vector can account for un-polarized, partially polarized, and full polarized light.
This study is aimed to improve the established four-channel Stokes vector based polarimeter, for better opto-mechanical configuration and greater stability of the system. The polarization state analyzer also includes photomultiplier (PMT), with gains as high as 108. Therefore, the signal-to-noise (S/N) ratio is critically sensitive to the light leakage from the environment. We modify the light tightness of the setup to improve the S/N ratio.
Generally, light propagation can be fully accounted by electromagnetic field, with the vector of the electric field representing polarization. The dielectric constant or index of refraction of bio-tissues or minerals would reflect the corresponding molecular structure, which may exhibit as anisotropy or birefringence. We have characterized some bio-samples by measuring the birefringence. Specifically, we are reporting the characterization of collagen through second harmonic (SH) signal by four-channel Stokes polarimeter.
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