High order Fano resonances and giant magnetic fields in dielectric microspheres

Wang, Zengbo; Luk’yanchuk, Boris; Yue, Liyang; Yan, Bing; Monks, James N.; Dhama, Rakesh; Minin, Igor V.; Huang, Sumei; Fedyanin, Andrey A.

doi:10.1038/s41598-019-56783-3

Cited by 57 publications

(121 citation statements)

References 37 publications

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“…[18] Yue et al and Wang et al studied focusing of specifically sized dielectric spheres in their publications and they thought the unusual Poynting vector circulation and Fano resonance could result in the extraordinary near-field focus with a large field intensity by a high-index sphere. [19,20] In the aspect of the experiment, Peppernick et al used to successfully observe a strong focus near the shadow surface of a polystyrene (PS) sphere (3 m diameter) on a platinum/palladium (Pt/Pd) substrate angularly illuminated by the 400 and 800 nm lasers with a photoemission electron microscopy (PEEM). [21] However, the refractive index of PS sphere at the wavelength of 400 and 800 nm (n = 1.63 and 1.58 [22] ) is much higher than that for Teflon in THz band (n = 1.43 [23] ); moreover, the additional factors, such as Pt/Pd substrate to enhance the collection of emitted electrons for PEEM and angular incidence of laser, complicated the formation of photonic jet and were significantly different from the conditions of the classic Lorenz-Mie theory as well.…”

Section: Introductionmentioning

confidence: 99%

Super‐Enhancement Focusing of Teflon Spheres

et al. 2020

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A Teflon (polytetrafluoroethylene) sphere can be used as a focusing lens in the applications of imaging and sensing due to its low-loss property in the terahertz band. Herein, field intensities and focusing parameters are analytically calculated for Teflon spheres at different low-loss levels and then a super-enhancement focusing effect in the spheres with particular size parameters was discovered, which can stimulate about 4000 times stronger field intensity than that for incident radiation as well as the great potential of overcoming diffraction limit despite high sensitivity to the magnitude of Teflon loss. A subsequent analysis of scattering amplitudes proves that the strong scattering of a single-order mode in the internal electric or magnetic field is the main factor causing this phenomenon.

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Section: Introductionmentioning

confidence: 99%

Super‐Enhancement Focusing of Teflon Spheres

et al. 2020

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“…This is currently in progress. A new physical effect -optical super resonance in microsphere due to high-order Fano resonance -could be another new route to achieve extreme super-resolution in PCM-objective and other microsphere-based techniques but will require a new modulated lighting source to match the super-resonance conditions [32].…”

Section: Theoretical Analysismentioning

confidence: 99%

Unibody microscope objective tipped with a microsphere: design, fabrication, and application in subwavelength imaging

et al. 2020

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Microsphere-based subwavelength imaging technique was first demonstrated in 2011. After nearly a decade of efforts, such technique has spawned numerous interests in fields such as laser nano-machining, imaging, sensing and biological detection. For wider industrial scale application of the technique, a robust, low-cost objective lens incorporating microsphere lens is highly desired and sought by many researchers. In this work, we demonstrate a unibody microscope objective lens formed by tipping a high-index microsphere onto a Plano-Convex lens and subsequently fitting them into a conventional objective lens. We call such new objective the Plano-Convex-Microsphere (PCM) objective, which resembles the appearance and operation of an ordinary microscope objective, while providing super-resolving power in discerning subwavelength nanoscale features in air condition. The imaging performance of PCM-objective along with the working distance has been systematically investigated. With the assistance of scanning process, larger area imaging is realized. The PCM-objective can be easily adaptive to many existing microscope systems and appealing for commercialization.

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“…A factor of 20-30 intensity enhancement due to the strong nanofocusing effect can be attained off-resonance; however, even stronger enhancements of both the electric and magnetic field are expected for resonant conditions. [36,48] For even larger ratios q ≫ 1, the nanofocusing effect can still be present but is size-independent with a maximum at the focal point approaching…”

Section: Energetic Considerationsmentioning

confidence: 99%

“…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%

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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High order Fano resonances and giant magnetic fields in dielectric microspheres

Cited by 57 publications

References 37 publications

Super‐Enhancement Focusing of Teflon Spheres

Super‐Enhancement Focusing of Teflon Spheres

Unibody microscope objective tipped with a microsphere: design, fabrication, and application in subwavelength 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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