Search

A 3-D, fully vectorial optical numerical model is used to design a high contrast grating for use as the top mirror of a 980-nm arsenide-based vertical-cavity surface-emitting laser. We study the parameters of two high contrast gratings made from GaAs/AlOx and Si/SiO x, respectively. Parameters providing high degrees of reflectivity, high levels of polarization discrimination, and fine tuning of the reflectivity of the high contrast grating are determined. The results demonstrate that both configurations if carefully designed by advanced numerical models can offer better performance in comparison to conventional distributed Bragg reflectors. [ABSTRACT FROM PUBLISHER]

We show the increase of the photoluminescence intensity ratio (PLR) and the emission rate enhancement of perovskite cesium lead bromide (CsPbBr3) and formamidinium lead bromide (FAPbBr3) nanocrystals (NCs) in the presence of single and double gold layer cavities, which we refer to as Metal-Emitter (ME) and Metal-Emitter-Metal (MEM) nanostructures. Up to 1.9-fold PLRs and up to 5.4-fold emission rate enhancements were obtained for FAPbBr3 NCs confined by double gold layers, which are attributed to plasmonic confinement from the gold layers. The experimentally obtained values are validated by analytical calculations and electromagnetic simulations. Such an effective method of manipulation of the spontaneous emission by simple plasmonic nanostructures can be utilized in sensing and detection applications. [ABSTRACT FROM AUTHOR]

Strong plasmonic resonance in the visible spectrum requires high aspect ratio metallic resonators with deep subwavelength dimensions, which find applications as part of a cost‐effective and practical optics‐based sensing platform. Electrodeposition is a highly suitable method for fabricating such structures as it allows deposition of metals with much larger thickness and better morphology than that achieved by physical deposition. Herein are presented an in‐depth study of pulsed electrodeposition of a gold film directly onto a transparent substrate without a seed layer and the development of a reliable and efficient fabrication method for high aspect ratio metallic nanostructures with sub‐10 nm features. Based on this approach, a low‐cost fabrication of sub‐100 nm metallic nanostructures is demonstrated with a very high deposition rate (up to 7 nm per pulse), yet with good surface morphology. Specifically, high aspect ratio rotationally symmetric plasmonic nanostructures suitable for a practical sensing platform are realized, exhibiting strong resonances in the visible spectrum with Q factors as high as 10 under unpolarized excitation. Pulsed electrodeposition is used to grow gold films directly onto indium tin oxide‐coated glass using various pulse parameters, and the results are compared using spectroscopy and electron microscopy. A suitable set of pulse parameters is then used to vertically grow gold nanostructures through a template, showing superior spectral characteristics to their planar conventionally deposited counterparts. [ABSTRACT FROM AUTHOR]

The article titled "Non-Invasive Super-Resolution Speckle Fluctuation Imaging" discusses a technique called non-invasive super-resolution speckle fluctuation imaging (NISSFI) that allows for the visualization of objects behind scattering media with sub-diffraction-limit resolution. By analyzing multiple speckle patterns from a fluctuating object within the optical memory effect region, high order cumulants are computed to reconstruct an image with reduced noise and improved resolution. The authors suggest that NISSFI has the potential for various applications, including nanometer-level resolution imaging of biological samples, tissues, bacteria, or viruses under the skin. [Extracted from the article]

Charge transfer plasmons (CTPs) in coupled plasmonic cavities have gained attention for their interesting resonance mechanisms and potential applications in sensing. The authors present the first investigation of the CTP mode in top‐down fabricated tall plasmonic nanostructures with deep nanogaps, whose excitation becomes possible by the interaction of transversal and longitudinal plasmonic modes. Hybridization of dipole and CTP modes at different parts of the plasmonic nanostructures, for both capacitively coupled dimer of sub‐5 nm gap and conductively coupled dimer with junction bridge is extensively studied. Importantly, the authors demonstrate the conditional emergence of a hybrid dimer‐CTP mode based on the cladding refractive index and analyte thickness, which can present an opportunity for highly specific surface sensing applications. The sensing performances of these modes are evaluated, showing a figure‐of‐merit of ≈18.4 and Q≈ 44 for the hybrid dimer‐CTP mode in the visible spectrum. Surface sensing based on alkanethiol adsorption shows surface sensitivity as high as ≈3.2 nm/carbon‐chain for this mode, which is higher than the typical values obtained by LSP structures. [ABSTRACT FROM AUTHOR]

We report a detailed comparative investigation of resonance behaviors and sensing capability of gold U-shape spilt-ring resonator (U-SRR) and fourfold rotated SRR (U4-SRR) metasurfaces in near- and middle-infrared (IR) range. All the resonant modes of the U4-SRR metasurfaces occur at longer wavelengths compared to the U-SRR metasurfaces with the same U size. Stronger field intensities are observed in all the three resonance modes of the U4-SRR metasurfaces and the intensity in the fundamental magnetic (m0) mode is almost three times of that of U-SRR metasurface under unpolarized incidence. All the three peak resonance wavelengths shift to longer wavelengths and the sensitivity increases with the increase of U size. A sensitivity of 642 nm RIU−1 is obtained in the U4-SRR metasurface for unpolarized incidence. This provides an excellent candidate for high performance sensing in the near- and mid-IR regions without polarization concern. [ABSTRACT FROM AUTHOR]

The nanoscale confinement of plasmonic fields, coupled with their high susceptibility to refractive index changes, makes localized surface plasmons (LSPs) an excellent platform for rapid and label‐free sensing. However, the small spatial overlap of the LSP fields with the adsorbed analyte dictates the sensitivity and figure of merit (FOM) of LSP‐based sensing. The linear dependence of sensitivity on resonance wavelength, coupled with the dependence of FOM on the achievable resonance Q factor, leads to a sensitivity of ≈100–300 nm per RIU and FOM < 5 for gold‐based LSP resonance in the visible range. This presents a dilemma for the realization of a practical sensing platform that requires high sensitivity and high FOM in the visible spectrum. Higher sensitivity and resonance Q factor can be achieved with a larger interaction volume between the plasmonic field and the analyte. This work explores a hybrid mode resulting from an interaction between transverse LSP and longitudinal Fabry–Perot (FP) modes, capable of improving the sensitivity and FOM simultaneously. This hybrid mode is demonstrated in tall v‐shaped split ring resonator structures, fabricated via seedless pulsed gold electrodeposition, with FOM of ≈24 in the visible range. [ABSTRACT FROM AUTHOR]