The divergent physical properties of light and sound waves result in tradeoffs between resolution and penetration depth with respect to their imaging capabilities. An ideal imaging system should combine the strengths of optical and acoustic imaging. Here, we demonstrate that via the use of designed metal nanoparticle based plasmonic metasurfaces, we can enable photoacoustic imaging with resolution better than optical imaging and penetration depths as deep as acoustic imaging, without any destruction of media, and with reduced power requirements (via plasmonic focusing). Moreover, the application to photoacoustic structured illumination microscopy would lead to new avenues in miniaturized, on-chip super-resolution imaging.
The origin and progression of a variety of leading health challenges, encompassing Alzheimer’s disease, heart disease, fibrosis and cancer, are directly linked to changes in the presence and orientation of fibrous matter in biological tissue. Fibrous biological tissue exhibits distinct anisotropic optical properties, which can be leveraged for selective imaging. However, these naturally occurring light-matter interactions are inherently weak, posing barriers to their visualization. Here, we leverage anisotropic, colorimetric metasurfaces to selectively visualize disease-relevant fiber density and orientation in biological tissue. We then investigate versatile fiber-affecting diseases where metasurfaces hold great potential to achieve rapid, precise and low-cost tissue diagnostics.
The polarization sensitivity of a nano-optical array is hypothesized to correlate with the degree of asymmetry of its individual nanostructures. This work takes a top-down approach to investigate how controlled violations of two-dimensional symmetry in regular polygon-shaped nanostructures affect the polarization sensitivity of lattice resonant, dielectric nano-arrays. Such nanoarrays dampen higher-order Mie resonances while maintaining the fundamental Mie resonance. Isolating a fundamental Mie resonance in the visible region of the electromagnetic spectrum permits the mapping of a spectrum to a high-purity color. Through this, it becomes possible to build a colorimetric sensor of domains of rotations of linearly polarized light.
Iridescent structural color is abundant in nature, arising in the saturated blues of the Morpho butterfly wing or the greens of jewelled beetle shells. At the micrometer scale and smaller, these naturally occurring, three-dimensionally (3D)-architected photonic crystals are composed of ordered, geometrically anisotropic features which exhibit distinct interactions with polarized light.
Here, we design artificial 3D-architected colorimetric metasurfaces. We use two-photon lithography to fabricate multilayer grating structures which surpass the polarization-sensitive colorimetric response attainable in nature. Bringing additive manufacturing to the regime of visible light-matter interactions, our metasurfaces hold promise for versatile imaging, display and sensing technologies.
Fibrotic diseases account for one-third of deaths worldwide, making it essential to investigate the accompanying tissue microstructural changes that are critical to disease progression. This research focuses on the fibrotic extracellular matrices present in histological tissue sections, which can characterize disease progression. We demonstrate how bioinspired structural color can be utilized as a label-free technology to determine disease progression on a single nanostructured surface. This nanophotonic imaging platform characterizes the organization of fibrous biological tissues with distinct stain-free color responses. The colorimetric response of histological tissue sections interfaced with these nanostructured slides was quantitatively assessed.
Imaging techniques with subdiffraction-limited spatial resolutions are highly desired for a deeper understanding of subcellular systems. Optical imaging enables high resolution under 200 nm while the visible light penetration depth is limited to merely 2 mm. Ultrasound images achieve two orders of magnitude lower resolutions but can penetrate two orders of magnitude deeper into a medium than optical images. This work combines the strengths of optical and acoustic imaging techniques through AuNP-based metasurfaces utilizing the photoacoustic effect that gold exhibits. Our novel imaging technique can simultaneously achieve high resolution and deep penetration depths without any destruction of media.
We present an all-optical, label-free technology for quantitative, real-time cancer tissue diagnostics on a single, clinically-compatible chip. Periodically-arranged sub-wavelength dielectric nanostructures, known as metasurfaces, are patterned into dielectric layers on glass microscope coverslips, where biopsied tumor tissue sections can be deposited following routine clinical procedure. We numerically and experimentally map the anisotropy and orientation of collagen fibers, a quantitative marker of cancer stage in tissue, onto metasurface structural color. Working at the interface of nanoscale optics and medicine, our colorimetric metasurface platform has the potential to set a new benchmark for rapid, quantitative and cost-effective cancer tissue diagnostics.
Optical chirality has been recently suggested to complement the physically relevant conserved quantities of the well-known Maxwell's equations. This time-even pseudoscalar is expected to provide further insight in polarization phenomena of electrodynamics such as spectroscopy of chiral molecules. Previously, the corresponding continuity equation was stated for homogeneous lossless media only. We extend the underlying theory to arbitrary setups and analyse piecewise-constant material distributions in particular. Our implementation in a Finite Element Method framework is applied to illustrative examples in order to introduce this novel tool for the analysis of time-harmonic simulations of nano-optical devices.
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