Optical Meta-Devices for Bio-Imaging

The novel property of optical meta-devices, which consist of meta-antenna made by artificial nanostructures, has attracted a lot of attention lately. Various optical devices based on the specific designs of meta-surfaces are called optical meta-devices. The great advantages of meta-devices are their new properties, lighter weight, small size, high efficiency, better performance, broadband operation, lower energy consumption, and CMOS compatibility for mass production. Given the demand for photonics, many optical meta-devices for the application and control of incident light are being quickly developed for beam deflection and reflection, polarization control and analysis, holography, second-harmonic generation, laser, tunability, imaging, absorption, color display, focusing of light, multiplex color routing, and light-field sensing. Here we demonstrated the optical meta-devices into bio-imaging. In this talk, we report 3 applications, varifocal Moiré meta-lens [1], Meta-lens based light-sheet fluorescent microscopy (MLSFM) [2], and abrupt autofocusing (AAF) meta-lens[3].<br/><br/>Following the Moiré technique, a variable focus dielectric meta-lens is designed and implemented for high-contrast optical sectioning fluorescence microscopy at the visible spectral region. The design principle of Moiré meta-lens and telecentric design is described in detail. We demonstrated telecentric imaging equipped with variable focus meta-lens, which performs high-contrast multi-plane fluorescence imaging for ex vivo mice intestine tissue samples. In addition, Moiré meta-lens-based fluorescence microscopy with the HiLo imaging principle provides fine optical sectioning with invariant image contrast through the entire scanning range. As a clear demonstration of imaging performance for our Moiré meta-lens-based microscope, both standard resolution target and fluorescent microspheres are imaged, with a lateral resolution of ~2 μm, as well as optical sectioning capability of ~7 μm. The varifocal Moiré meta-lens with ultra-thin size and compact design may replace its counterpart in any optical system that requires a focus-tunable lens, such as optical coherence tomography and micro-endoscopy for in vivo imaging.<br/><br/>We show the implementation of a metasurface optical element in LSFM for imaging lives biological samples as well. The performance of our LSFM was evaluated by utilizing standard fluorescent microspheres and in vivo imaging of fine structures associated with the developmental process in live C. elegans. Results obtained from our systems clearly show internal structures of the C. elegans up to cellular resolution for multiple wavelengths. Experimental measurements are compared with the conventional LSFM systems (i.e., without any meta-lenses), and similar image resolution is demonstrated. The results clearly illustrate the capability of the system for biomedical imaging applications. Moreover, the significance of the present techniques lies in the fact that the complexity of the instrument in the illumination is entirely reduced, from tens of centimeters to 800 nm, without affecting any imaging performance, which clearly shows great potential to utilize metasurface optics for miniaturizing microscopic imaging instruments. Applications of meta-lens can be readily extended to illumination, as well as in the detection of LSFM to include all the essential features of meta-surfaces. Metasurface optics can be utilized for many LSFM modalities to achieve novel functionalities, such as meta-lens arrays for light-sheet generation, multi-view/multi-dimensional selective plane illumination microscopy, near-infrared and multi-photon LSFM. Further, by integrating beam shaping techniques in the meta-lens design, exotic light-sheet patterns with an extended field of view and smaller thickness can be achieved. We believe this work is an advancement of the applications of meta-devices in microscopy.