Raum 97, ExWi, Sidlerstrasse 5, 3012 Bern Seminareinladung_MW_WitaliKrochin_Ground-based temperature remote-sensing in the middle atmosphere 01 October
Backscattering polarimetric imaging of the human brain to determine the orientation and degree of alignment of nerve fiber bundles The nerve fiber bundles constitutive of the white matter in the brain are organized in such a way that they exhibit a certain degree of structural anisotropy and birefringence. The birefringence exhibited by such aligned fibrous tissue is known to be extremely sensitive to small pathological alterations. Indeed, highly aligned anisotropic fibers exhibit higher birefringence than structures with weaker alignment and anisotropy, such as cancerous tissue. In this study, we performed experiments on thick coronal slices of a healthy human brain to explore the possibility of (i) measuring, with a polarimetric microscope the birefringence exhibited by the white matter and (ii) relating the measured birefringence to the fiber orientation and the degree of alignment. This is done by analyzing the spatial distribution of the degree of polarization of the backscattered light and its variation with the polarization state of the probing beam. We demonstrate that polarimetry can be used to reliably distinguish between white and gray matter, which might help to intraoperatively delineate unstructured tumorous tissue and well organized healthy brain tissue. In addition, we show that our technique is able to sensitively reconstruct the local mean nerve fiber orientation in the brain, which can help to guide tumor resections by identifying vital nerve fiber trajectories thereby improving the outcome of the brain surgery.
Perspective on the next generation of ultra-low noise fiber supercontinuum sources andtheir emerging applications in spectroscopy,imaging, and ultrafast photonics A new generation of ultrafast and low-noise supercontinuum (SC) sources is currently emerging, driven by the constantly increasingdemands of spectroscopy, advanced microscopy, and ultrafast photonics applications for highly stable broadband coherent light sources. Inthis Perspective, we review recent progress enabled by advances in nonlinear optical fiber design, detail our view on the largely untappedpotential for noise control in nonlinear fiber optics, and present the noise fingerprinting technique for measuring and visualizing the noise ofSC sources with unprecedented detail. In our outlook, we highlight how these SC sources push the boundaries for many spectroscopy andimaging modalities and focus on their role in the development of ultrafast fiber lasers and frequency combs with ultra-low amplitude andphase noise operating in the 2lm spectral region and beyond in the mid-IR.
