Polarization-sensitive second harmonic confocal imaging of biological tissues

Among the many collagen-rich tissues, we studied rat-tail tendon in detail since it is composed of highly-organized type I collagen fibrils. We devised a confocal microscope that measures the second harmonic light generated from rat-tail tendon. Since SHG is sensitive to the linear polarization of the excitation pulse, a mathematical model was developed to investigate the relationship between linear polarization, the direction of the collagen fibrils, and the intensity of the generated second harmonic light. Also, the effect of collagen organization on the second harmonic intensity was studied.