We propose an analytical solution of the focal ring generated at the focus of a toric lens. The analytical field of the focal ring is used with a Fourier transform lens to generate a Bessel beam. A comparative analysis between the use of an illuminated annular aperture, an axicon, and a toric lens to generate a Bessel beam is performed, and the benefits and drawbacks of each are discussed. This highlights the advantages of using a toric lens with a Gaussian beam to produce a focal line of increasing intensity, which is advantageous for applications such as high depth-of-field microscopy.
Diffusion in nature is usually considered as a smooth redistribution process. However, it appears that the diffusion of chiral molecules and the propagation of chirality may proceed in quite different ways. Indeed, in the present work, unexpected quantization of the spatial concentration of chiral molecules is discovered in self-aligned molecular liquids. It is shown that the interpenetration of two liquids is forming discrete diffusion barrier walls resulting in steplike concentration distribution of chiral molecules in space. The concentration gradient is at least an order of magnitude stronger from both sides of the barrier wall compared to the gradient between those walls. It is also shown that this microscopic diffusion process may be controlled by macroscopic boundary conditions imposed on the host molecular system. Both of those phenomena are related to the collective long-range orientational "elastic" interactions of molecules of the host. The observed phenomena may radically change our understanding of diffusion of chiral molecules, among others, in biological tissue, which contains many examples of self-aligned molecular liquids. This, in turn, has the potential to revolutionize drug design and delivery techniques.
Typical light sheet microscopes suffer from artifacts related to the geometry of the light sheet. One main inconvenience is the non-uniform thickness of the light sheet obtained with a Gaussian laser beam.Aim: We developed a two-photon light sheet microscope that takes advantage of a thin and long Bessel-Gauss beam illumination to increase the sheet extent without compromising the resolution.Approach: We use an axicon lens placed directly at the output of an amplified femtosecond laser to produce a long Bessel-Gauss beam on the sample. We studied the dopaminergic system and its projections in a whole cleared mouse brain.Results: Our light sheet microscope allows an isotropic resolution of 2.4 μm in all three axes of the scanned volume while keeping a millimetric-sized field of view, and a fast acquisition rate of up to 34 mm 2 ∕s. With slight modifications to the optical setup, the sheet extent can be increased to 6 mm.
Conclusion:The proposed system's sheet extent and resolution surpass currently available systems, enabling the fast imaging of large specimens.
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