부산대학교 도서관

Polarised nonlinear microscopy has been extensively developed to study molecular organisation in biological tissues, quantifying the response of nonlinear signals to a varying incident linear polarisation. Polarisation Second harmonic Generation (PSHG) in particular is a powerful tool to decipher sub‐microscopic modifications of fibrillar collagen organisation in type I and III collagen‐rich tissues. The quality of SHG imaging is however limited to about one scattering mean free path in depth (typically 100 micrometres in biological tissues), due to the loss of focus quality, induced by wavefront aberrations and scattering at even larger depths. In this work, we study how optical depth penetration in biological tissues affects the quality of polarisation control, a crucial parameter for quantitative assessment of PSHG measurements. We apply wavefront shaping to correct for SHG signal quality in two regimes, adaptive optics for smooth aberration modes corrections at shallow depth, and wavefront shaping of higher spatial frequencies for optical focus correction at larger depths. Using nonlinear SHG active nanocrystals as guide stars, we quantify the capabilities of such optimisation methods to recover a high‐quality linear polarisation and investigate how this approach can be applied to in‐depth PSHG imaging in tissues, namely tendon and mouse cranial bone. LAY DESCRIPTION: Biomolecular organization in tissues is a key element to many biological functions. Disorder of proteins and lipids assemblies is in particular associated to the development of pathologies, therefore quantifying such disorder is important for their molecular‐scale understanding. Quantifying molecular order is possible in optical microscopy thanks to the manipulation of light polarization. In this work, we explore how polarization sensitive microscopy is degraded when optical imaging is performed in scattering tissues at large depths (typically hundreds of micrometers), and how to correct for this degradation thanks to phase front correction of light propagation distortions. We show that in wavefront correction is generally correlated to polarization quality recovery at large depths. [ABSTRACT FROM AUTHOR]