Adaptive-Optics Polarization-Sensitive Second Harmonic Generation Microscopy

An accurate visualization of structures containing collagen is essential for early detection and correct diagnosis of possible diseases. Second harmonic generation (SHG) microscopy is a non-invasive multiphoton technique allowing high-resolution imaging of collagen-based structures. However, this technique is limited by optical aberrations. Adaptive optics (AO) procedures are often used to compensate for optical aberrations and to improve multiphoton imaging. Moreover, since polarization modulates SHG signal, the acquired images show different features depending on the incident polarization state. In this work we demonstrate a multiphoton microscope combining AO and polarization-control for SHG imaging. Results show that polarization adds extra benefits to AO in terms of image quality enhancement. Although the performance depends on each particular sample and depth imaging location, results show up to a 3× improvement in SHG signal.