2021, Cifuentes, Angel, Pikálek, Tomáš, Ondráčková, Petra, Amezcua-Correa, Rodrigo, Antonio-Lopez, José Enrique, Čižmár, Tomáš, Trägårdh, Johanna

Multimode fiber-based endoscopes have recently emerged as a tool for minimally invasive endoscopy in tissue, at depths well beyond the reach of multiphoton imaging. Here, we demonstrate label-free second-harmonic generation (SHG) microscopy through such a fiber endoscope. We simultaneously fully control the excitation polarization state and the spatial distribution of the light at the fiber tip, and we use this to implement polarization-resolved SHG imaging, which allows imaging and identification of structural proteins such as collagen and myosin. We image mouse tail tendon and heart tissue, employing the endoscope at depths up to 1 mm, demonstrating that we can differentiate these structural proteins. This method has the potential for enabling instant and in situ diagnosis of tumors and fibrotic conditions in sensitive tissue with minimal damage.

2021, Ruder, Alexander, Wright, Brandon, Feder, Rene, Kilic, Ufuk, Hilfiker, Matthew, Schubert, Eva, Herzinger, Craig M., Schubert, Mathias

We demonstrate calibration and operation of a Mueller matrix imaging microscope using dual continuously rotating anisotropic mirrors for polarization state generation and analysis. The mirrors contain highly spatially coherent nanostructure slanted columnar titanium thin films deposited onto optically thick titanium layers on quartz substrates. The first mirror acts as polarization state image generator and the second mirror acts as polarization state image detector. The instrument is calibrated using samples consisting of laterally homogeneous properties such as straight-through-air, a clear aperture linear polarizer, and a clear aperture linear retarder waveplate. Mueller matrix images are determined for spatially varying anisotropic samples consisting of a commercially available (Thorlabs) birefringent resolution target and a spatially patterned titanium slanted columnar thin film deposited onto a glass substrate. Calibration and operation are demonstrated at a single wavelength (530 nm) only, while, in principle, the instrument can operate regardless of wavelength. We refer to this imaging ellipsometry configuration as rotating-anisotropic-mirror-sample-rotating-anisotropic-mirror ellipsometry (RAM-S-RAM-E).