All-dielectric concentration of electromagnetic fields at the nanoscale: the role of photonic nanojets

Zhu, Jinlong; Goddard, Lynford L.

doi:10.1039/c9na00430k

Cited by 62 publications

(32 citation statements)

References 319 publications

(374 reference statements)

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“…Despite imaging occurring in the far field, it has been proposed that the SR effect of PNJs has a strong near-field component [ 41 , 42 ]. To further understand this phenomenon, simulations were performed for both 14 and 60 µm diameter spheres using Gaussian beam illumination with a numerical aperture (NA) of 1.2 as used in experiments.…”

Section: Resultsmentioning

confidence: 99%

Superresolved polarization-enhanced second-harmonic generation for direct imaging of nanoscale changes in collagen architecture

Johnson

Karvounis

Singh

et al. 2021

Optica

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Superresolution (SR) optical microscopy has allowed the investigation of many biological structures below the diffraction limit; however, most of the techniques are hampered by the need for fluorescent labels. Nonlinear label-free techniques such as second-harmonic generation (SHG) provide structurally specific contrast without the addition of exogenous labels, allowing observation of unperturbed biological systems. We use the photonic nanojet (PNJ) phenomena to achieve SR-SHG. A resolution of with respect to the fundamental wavelength, that is, a -fold improvement over conventional or diffraction-limited SHG under the same imaging conditions is achieved. Crucially we find that the polarization properties of excitation are maintained in a PNJ. This is observed in experiment and simulations. This may have widespread implications to increase sensitivity by detection of polarization-resolved SHG by observing anisotropy in signals. These new, to the best of our knowledge, findings allowed us to visualize biological SHG-active structures such as collagen at an unprecedented and previously unresolvable spatial scale. Moreover, we demonstrate that the use of an array of self-assembled high-index spheres overcomes the issue of a limited field of view for such a method, allowing PNJ-assisted SR-SHG to be used over a large area. Dysregulation of collagen at the nanoscale occurs in many diseases and is an underlying cause in diseases such as lung fibrosis. Here we demonstrate that pSR-SHG allows unprecedented observation of changes at the nanoscale that are invisible by conventional diffraction-limited SHG imaging. The ability to nondestructively image SHG-active biological structures without labels at the nanoscale with a relatively simple optical method heralds the promise of a new tool to understand biological phenomena and drive drug discovery.

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Section: Resultsmentioning

confidence: 99%

Superresolved polarization-enhanced second-harmonic generation for direct imaging of nanoscale changes in collagen architecture

Johnson

Karvounis

Singh

et al. 2021

Optica

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“…The fibrous cytoskeleton and bilayer membrane of cells were clearly illustrated with the help of biomagnifiers, which were unobtainable by the traditional microscope. The most striking advantage of cell-based biomagnifier over conventional optical microscopes is that the imaging can be conducted in a contact mode, so the possible evanescent-propagation coupling may contribute to super-resolution imaging 169 . This cell-based bio-microlens were also exploited for fluorescence enhancement.…”

Section: Cell-based Bio-microlensesmentioning

confidence: 99%

Biophotonic probes for bio-detection and imaging

Pan

Xin

et al. 2021

Light Sci Appl

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The rapid development of biophotonics and biomedical sciences makes a high demand on photonic structures to be interfaced with biological systems that are capable of manipulating light at small scales for sensitive detection of biological signals and precise imaging of cellular structures. However, conventional photonic structures based on artificial materials (either inorganic or toxic organic) inevitably show incompatibility and invasiveness when interfacing with biological systems. The design of biophotonic probes from the abundant natural materials, particularly biological entities such as virus, cells and tissues, with the capability of multifunctional light manipulation at target sites greatly increases the biocompatibility and minimizes the invasiveness to biological microenvironment. In this review, advances in biophotonic probes for bio-detection and imaging are reviewed. We emphatically and systematically describe biological entities-based photonic probes that offer appropriate optical properties, biocompatibility, and biodegradability with different optical functions from light generation, to light transportation and light modulation. Three representative biophotonic probes, i.e., biological lasers, cell-based biophotonic waveguides and bio-microlenses, are reviewed with applications for bio-detection and imaging. Finally, perspectives on future opportunities and potential improvements of biophotonic probes are also provided.

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“…Light interaction with dielectric microparticles of sizes larger than the laser wavelength gives rise to photonic jet nanofocusing in air, [25,39,48] accompanied by extreme electric and magnetic field enhancement on the scale of a few laser wavelengths. Light confinement inside the photonic nanojet and laser-induced free carrier generation in ambient air are two associated processes, which are relevant for a variety of applications.…”

Section: Field Enhancement and Free Carriers In Airmentioning

confidence: 99%

“…Finally, microparticles larger than laser wavelength are shown to be the sources for extreme energy concentration in their elongated near-field focal point in air, known as photonic nanojets, with potential applications to nanoscope optical imaging, nanofabrication, or dry laser cleaning. [25,38,39] In our work, we elucidate how the maximum electric fields are affected by plasma shielding inside the droplet. We show as well that the optical breakdown in air due to the presence of large water droplets may occur much below the thresholds for pure air or liquid bulk water, creating subwavelength plasma filaments with nonlocal sources of free carriers.…”

mentioning

confidence: 99%

Tunable Near‐ to Far‐Infrared Optical Breakdown in Nonlinear Interactions of Ultrashort Laser Pulses with Water Microdroplets in Ambient Air

Rudenko

Moloney

2020

Advanced Photonics Research

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Water droplets are omnipresent in biophysical environments and ecosystems, playing an important role in communication through the atmosphere (i.e., aerosols and contaminants, fog, mist, haze, drizzle, clouds) and being involved in a variety of physicochemical reactions and biological processes (respiratory droplets due to breathing, talking, coughing, etc., biological cells, bioaerosols, water clusters, surface adhesion, and wettability). Broad opportunities in analysis, detection, and control over droplet distributions are enabled by the application of powerful lasers used for laser breakdown, [1-3] electron photoemission [4-7] and cavity-enhanced droplet spectroscopy, [8,9] long-distance optical communications, [10-12] and high harmonic generation from water microdroplets. [13-15] The processes of ultrashort laser excitation and ionization of water droplets and aerosols remain poorly explored for a wide range of photon energies and wavelengths from visible to long-wave infrared (IR) range. Within this spectral range, the contributions of scattering and absorption in water, [16] photo-and avalanche ionization, [17,18] positive and negative transient refractive index modifications due to free carrier heating, [19,20] as well as diffraction, Kerr self-focusing, and plasma defocusing upon propagation in the atmosphere [21-23] play interchangeable roles, making indispensable a comprehensible broad-frequency study of laser-induced nonlinear processes and optical breakdowns in laser-droplet interactions. Our current study addresses aspects of high-intensity femtosecond laser interaction with a single water microdroplet in ambient air for a wide range of laser wavelengths. Depending on the droplet size and wavelength (in Rayleigh, Mie, or geometrical optics [GO] ranges [24]), different complex field patterns are induced inside the droplet, contributing to extreme energy confinement due to a nanofocusing effect. [25] Such strong intensities result in electron plasma generation inside the droplets due to photo-and avalanche ionization processes, [11,26-30] changing locally the transient optical properties of water, influencing pulse propagation, and contributing to strong absorption. The effect of nanoscale electron plasma confinement inside microdroplets is comparable to ultrashort laser-induced plasma formation in the vicinity of plasmonic nanoparticles, routinely used for cancer cell phototherapy and viral or bacterial inactivation by selective nanobubble cavitation in water. [31-33] In fact, the pronounced absorption at the nanoscale in both cases reduces significantly the threshold for permanent modification, i.e., phase explosion [34] and cavitation via shock waves, produced by temperature gradients. [12,31,35] Knowledge of the minimum energy required to damage the droplet is relevant for high-repetition rate optical communications (e.g., fog clearing), [11,12] for laser spectroscopy, [2,3] and for biomedical applications (e.g., surface cleaning or airborne virus detection and inactivation in the respiratory drople...

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All-dielectric concentration of electromagnetic fields at the nanoscale: the role of photonic nanojets

Abstract: This article gives a thorough and unprecedented review that presents new perspectives, unusual physics, and exciting trends for photonic nanojets.

Cited by 62 publications

References 319 publications

Superresolved polarization-enhanced second-harmonic generation for direct imaging of nanoscale changes in collagen architecture

Superresolved polarization-enhanced second-harmonic generation for direct imaging of nanoscale changes in collagen architecture

Biophotonic probes for bio-detection and imaging

Tunable Near‐ to Far‐Infrared Optical Breakdown in Nonlinear Interactions of Ultrashort Laser Pulses with Water Microdroplets in Ambient Air

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