The diffraction limit is a fundamental barrier in optical microscopy, restricting the smallest resolvable feature size of a microscopic imaging system. Microsphere-assisted super-resolution microscopy has emerged as a promising approach for overcoming this limit. This technique offers several advantages, including no need of fluorescent dyes, easy operation under white light illumination, and good compatibility with commercial optical microscopes. Various strategies have been proposed to enhance the imaging performance of microspheres. Recently, patchy microspheres were found to exhibit super-resolution capabilities in air with an enhanced imaging contrast. In this work, we studied the super-resolution imaging performance of patchy microspheres fully immersed in liquid. Furthermore, we demonstrated the formation of photonic hooks from patchy microspheres within a liquid environment. The findings of this study will extent the application of patchy microspheres from air to liquid immersion mode, opening up new possibilities for super-resolution imaging in liquid environment with patchy microspheres.
Plasmonic nanoparticles are desirable for a wide range of applications and act as the base nano-building blocks for thin film optics and optical metamaterials. The properties and applicability of plamsonic materials are considerably influenced by their size, shape, charge, and agglomeration, all of which contribute to their optical properties. There is a range of top-down and bottom-up engineering processes now available for synthesizing these nanomaterials. However, the majority of current fabrication methods are thermally based which give rise to broad particle polydispersity and require strong reducing agents. Our research has developed a new nanoengineering instrument that is capable of synthesizing plasmonic nanoparticles to a desired optical specification. This novel synthesizing method provides excellent spatial and temporal control, avoids harmful strong reducing agents, and can be synthesis at room temperature. The underlying technology functionalizes seed nanoparticles and utilizes a photochemical reaction to activate the higher order plasmon modes from a seed nanoparticle solution to finely tailor the morphology of the nanoparticles in order to provide a desired optical response. This is achieved through intramolecular α-hydrogen abstraction of arylcycloalkyl ketones through the Norrish type II reaction. The end product yields a colloidal solution with optical properties that have been tuned and tailored by pure spectral radiation. Utilizing this technology could enable a manufacturing route for optical metamaterial building blocks in a repeatable and reliable fashion that assist hierarchical assembly techniques.
The development of shift-free fixed-line filters is a key technology for advancing the next generation of laser protection and is greatly desired due to the increased threat of laser attacks. Thin-film interference coatings have remained the key technology for achieving narrow bandstop filters for protection against laser light since the late 1970s. This paper presents the latest developments in fixed-line laser technology and introduces a metamaterial solution to mitigate the angular shift found in thin-film interference coatings. The metamaterial coating consists of metallic nano-particles periodically distributed within a non-absorbing dielectric material with a specific refractive index that enables the desired plasmonic resonance to exist at wavelengths that match that of the lasers. Due to the nano-particle size, the metamaterial layer can be treated as an individual homogeneous layer with properties described by an effective Drude-Lorentz approximation model. Unlike standard interference coatings where the effective index of the stack decreases with larger angles of incidence, the metamaterial’s effective index remains relatively fixed with increasing angles resulting in the narrow bandstop function remaining shift-free.
During last several years it was shown, that an electromagnetic field can be made to curve after propagation through a simple dielectric mesoscale Janus particle of special shape, which adds a newfound degree of simplicity. This effect was discovered by I.V.Minin and O.V.Minin and termed ‘photonic hooks’– it is an unique electromagnetic self-bending subwavelength structured light beams configuration behind a mesoscale particle with a broken symmetry and differ from Airy-family beams. PH features the radius of curvature, which is about 2 times smaller than the electromagnetic wavelength - this is the smallest curvature radius of electromagnetic waves ever reported. The nature of a photonic hook is in dispersion of the phase velocity of the waves inside of particle, resulting in interference. Here, we report an experimental verification of the photonic hook effect in terahertz waveband.
KEYWORDS: Particles, Nanoparticles, Laser ablation, Gold, Plasmonics, Near field optics, Near field scanning optical microscopy, Nanostructures, Scanning electron microscopy, Plasmons
Ablation with nanoscale spatial resolution needs special tools to overcome conventional diffraction limit. A few methods
have been successfully applied for this purpose. These include: surface nanostructuring by laser illuminated tip; Near-field
Scanning Optical Microscopy (NSOM) nano-patterning; Surface nano-processing based on optical resonances and
near-field effects with transparent particles as well as the field enhancement by plasmonic nanoparticles. All these
methods permit localized laser ablation on the scale beyond 100 nm. In this paper we report our recent work related to
field enhancement by laser illuminated tip, near-field laser ablation with transparent particles and field enhancement by
plasmonic effects.
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