Generally, chemical tissue clearing is performed by a solution consisting of two parts benzyl benzoate and one part benzyl alcohol. However, prolonged exposure to this mixture markedly reduces the fluorescence of GFP expressing specimens, so that one has to compromise between clearing quality and fluorescence preservation. This can be a severe drawback when working with specimens exhibiting low GFP expression rates. Thus, we screened for a substitute and found that dibenzyl ether (phenylmethoxymethylbenzene, CAS 103-50-4) can be applied as a more GFP-friendly clearing medium. Clearing with dibenzyl ether provides improved tissue transparency and strikingly improved fluorescence intensity in GFP expressing mouse brains and other samples as mouse spinal cords, or embryos. Chemical clearing, staining, and embedding of biological samples mostly requires careful foregoing tissue dehydration. The commonly applied tissue dehydration medium is ethanol, which also can markedly impair GFP fluorescence. Screening for a substitute also for ethanol we found that tetrahydrofuran (CAS 109-99-9) is a more GFP-friendly dehydration medium than ethanol, providing better tissue transparency obtained by successive clearing. Combined, tetrahydrofuran and dibenzyl ether allow dehydration and chemical clearing of even delicate samples for UM, confocal microscopy, and other microscopy techniques.

Beam modes are considered by a high-aperture scalar theory based on the complex source-point method. A different form for the beam mode that avoids nonphysical singularities in intensity is introduced. The amplitude in the focal region is explored for the lowest-order mode. Conditions for oscillation of a high-aperture resonator, such as a microcavity, are derived. The amplitude in the focal region is explored for higher-order modes in systems with cylindrical symmetry. These modes are expressed in terms of Jacobi polynomials.

A tailored protocol combines pigment removal with clearing, facilitating labeling and whole-body imaging across phylogeny.

The lowest-order Gaussian beam mode is considered in a high-aperture theory based on a new variation of the complex source point model. To avoid singularities, combinations of sources and sinks are assumed. The resultant beam is a rigorous solution of Maxwell’s equations for all space that reduces to the conventional Gaussian beam in the paraxial limit and that is physically realizable. The field in the region of the waist and far from the waist is explored. It is demonstrated that direct rigorous evaluation of the field is feasible.

An alternative set of eigensolutions of the paraxial wave equation to that of the ordinary Hermite-Gaussian modes is that of the so-called ‘elegant’ Hermite-Gaussian modes. The analogous elegant Laguerre-Gaussian modes are derived. The near- and far-field behaviours of the elegant Hermite-Gaussian and Laguerre-Gaussian modes are investigated. The similarity between the elegant Laguerre-Gaussian beams and the Bessel-Gaussian beams is discussed.