Abstract
Light sheet microscopy (LSM) - also known as selective plane illumination microscopy (SPIM) - enables high-speed, volumetric imaging by illuminating a two-dimensional cross-section of a specimen. Typically, this light sheet is created by table-top optics, which limits the ability to miniaturize the overall SPIM system. Replacing this table-top illumination system with miniature, integrated devices would reduce the cost and footprint of SPIM systems. One important element for a miniature SPIM system is a flat, easily manufactured lens that can form a light sheet. Here we investigate planar metallic lenses as the beam shaping element of an integrated SPIM illuminator. Based on finite difference time domain (FDTD) simulations, we find that diffraction from a single slit can create planar illumination with a higher light throughput than zone plate or plasmonic lenses. Metallic slit microlenses also show broadband operation across the entire visible range and are nearly polarization insensitive. Furthermore, compared to meta-lenses based on sub-wavelength-scale diffractive elements, metallic slit lenses have micron-scale features compatible with low-cost photolithographic manufacturing. These features allow us to create inexpensive integrated devices that generate light-sheet illumination comparable to tabletop microscopy systems. Further miniaturization of this type of integrated SPIM illuminators will open new avenues for flat, implantable photonic devices for in vivo biological imaging.
Highlights
Optical microcopy is an increasingly powerful tool for biology thanks to a growing library of fluorescent reporters and optical methods to manipulate cell activity [1,2,3,4,5,6]
To improve 3D imaging speed, several groups have demonstrated a technique known as light-sheet microscopy (LSM) [1,10,11,12] or selective plane illumination microscopy (SPIM) [13,14,15,16] that focuses excitation light not to a single spot but rather a thin 2D plane
Compared to zone plate lenses and plasmonic nano-slit lenses we find that optical throughput through a micron-scale metallic slit is much higher while producing similar light sheet illumination patterns
Summary
Optical microcopy is an increasingly powerful tool for biology thanks to a growing library of fluorescent reporters and optical methods to manipulate cell activity [1,2,3,4,5,6]. Meta-lenses have shown performance similar to Fresnel lenses based on planar nanofabrication processes [25,26] While these lenses show great promise for a number of applications, their requirement for subwavelength features that necessitates nanofabrication processes like electron beam lithography can significantly increase the cost of the lenses, making it more difficult to create arrays of low-cost SPIM systems. Compared to zone plate lenses and plasmonic nano-slit lenses we find that optical throughput through a micron-scale metallic slit is much higher while producing similar light sheet illumination patterns. To reduce absorption losses one could adjust the radiation pattern of the source to better fill the aperture, or exploit more advanced fabrication techniques to produce metasurfaces based on high-aspect-ratio and low absorption loss titanium dioxide [25]
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