Light-sheet fluorescence microscopy has greatly improved the speed and overall photostability of optically sectioning cellular and multi-cellular specimens. Similar gains have also been conferred by light-sheet Raman imaging; these schemes, however, rely on diffraction limited Gaussian beams that hinder the uniformity and size of the imaging field-of-view, and, as such, the resulting throughput rates. Here, we demonstrate that a digitally scanned Airy beam increases the Raman imaging throughput rates by more than an order of magnitude than conventional diffraction-limited beams. Overall, this, spectrometer-less, approach enabled 3D imaging of microparticles with high contrast and 1 µm axial resolution at 300 msec integration times per plane and orders of magnitude lower irradiation density than coherent Raman imaging schemes. We detail the apparatus and its performance, as well as its compatibility with fluorescence light-sheet and quantitative-phase imaging towards rapid and low phototoxicity multimodal imaging.
A new technology that includes a flexible holographic recording system using photo-thermo-refractive (PTR) glass is demonstrated for creating so-called 'holographic phase masks' or HPMs. These diffractive optical elements are permanently recorded in the PTR glass, can be multiplexed as with normal holograms, do not require electric power to operate, and can perform near arbitrary beam phase transformations. The holographic setup includes a spatial light modulator that enables recording transmitting volume Bragg gratings (VBGs) with arbitrary phase patterns encoded into them. As a result, the desirable phase pattern is introduced in a beam that is diffracted by the VBG. These HPMs are tunable within the visible and near IR spectral regions and can be made achromatic, with spectral widths of up to 50 nm. Furthermore, they tolerate laser power densities on the order of several kW cm −2 . Applications of HPMs include high-power, broadband laser beam shaping and modal analysis of complex beams profiles, both of which are demonstrated here.
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