Video-rate Raman-based metabolic imaging by Airy light-sheet illumination and photon-sparse detection.

Despite its massive potential, Raman imaging represents just a modest fraction of all research and clinical microscopy to date. This is due to the ultralow Raman scattering cross-sections of most biomolecules that impose low-light or photon-sparse conditions. Bioimaging under such conditions is suboptimal, as it either results in ultralow frame rates or requires increased levels of irradiance. Here, we overcome this tradeoff by introducing Raman imaging that operates at both video rates and 1,000-fold lower irradiance than state-of-the-art methods. To accomplish this, we deployed a judicially designed Airy light-sheet microscope to efficiently image large specimen regions. Further, we implemented subphoton per pixel image acquisition and reconstruction to confront issues arising from photon sparsity at just millisecond integrations. We demonstrate the versatility of our approach by imaging a variety of samples, including the three-dimensional (3D) metabolic activity of single microbial cells and the underlying cell-to-cell variability. To image such small-scale targets, we again harnessed photon sparsity to increase magnification without a field-of-view penalty, thus, overcoming another key limitation in modern light-sheet microscopy.

Network analysis of Weyl semimetal photogalvanic systems.

We develop a general methodology capable of analyzing the response of Weyl semimetal (WSM) photogalvanic networks. Both single-port and multiport configurations are investigated via extended versions of Norton's theorem. An equivalent circuit model is provided where the photogalvanic currents induced in these gapless topological materials can be treated as polarization-dependent sources. To illustrate our approach, we carry out transport simulations in arbitrarily shaped configurations involving pertinent WSMs. Our analysis indicates that the photogalvanic currents collected in a multi-electrode system directly depend on the geometry of the structure as well as on the excitation and polarization pattern of the incident light. Our results could be helpful in designing novel optoelectronic systems that make use of the intriguing features associated with WSMs.