Polarization-resolved Second Harmonic Generation microscopy in biological tissues

In this study, we implemented a polarimetric SHG microscope and analyzed the linear propagation effects that affect polarization-resolved SHG imaging of thick anisotropic collagenous tissues. We developed a theoretical model to account for birefringence and diattenuation along the excitation propagation, and polarization scrambling upon scattering of the harmonic signal. We obtained an excellent agreement with polarization-resolved SHG images at increasing depth within a rat-tail tendon for both polarizations of the forward SHG signal (see Figure 1). Most notably, we observed interference fringes due to birefringence in the SHG depth profile when excited at π/4 angle from the tendon axis.