Spectroscopic Study of Second Harmonic Generation Chiral Microscopy in Type I Collagen

Chiral molecules have different efficiencies in generating second-harmonic generation signal for left- and right-circular-polarized light. This effect is called second-harmonic generation circular dichroism (SHG-CD). It has been shown that SHG-CD exhibits much better chiral contrast than traditional chiroptical spectroscopies [1]. Furthermore, combined with a laser scanning microscope, SHG-CD provides optical sectioning capability that is suitable for examining thick tissue samples. We have shown that type I collagen gives rise to strong second-harmonic generation circular dichroism (SHG-CD) responses [2]. However, to resolve the molecular structures and chiral properties of biological tissues, it is not enough to study SHG-CD for only one specific wavelength.