Optically induced hyperthermia is an actively developing approach to treating cancer. All-dielectric nanoparticles have established themselves in different biomedical applications, including optical heating and nanothermometry. However, this type of nanoparticles (NPs) do not provide sufficient heating due to the necessity for a narrow size distribution. Thus, size-separation is required. Other method of negating disadvantages of all-dielectric NPs is incorporating plasmonic nanoparticles to create hybrid nanostructure, which would be less sensitive to size distribution, making it great nanoheater and nanothermometer. In this work, we propose a simple way of fabricating hybrid silicon-gold (Si-Au) NPs. We compare hybrid nanoparticles with pristine monodisperse Si NPs. In addition, we perform optical heating and simultaneous nanothermometry inside and outside living B16-F10 melanoma cells. Results reveal, that the hybrid NPs are more efficient in biological environments, since inhomogeneous medium can make it difficult to fulfill the critical coupling conditions.
Bound states in the continuum (BICs) represent dark modes trapped in the radiation continuum. BICs received significant attention in optics and photonics as a simple tool to achieve giant quality factors by transforming them into quasi-BICs. Here, we report the observation of high-harmonic generation in dielectric metasurfaces hosting BICs. The metasurface is composed of a square lattice with parallel Si bars of a slightly different width placed on a transparent substrate. The structure is engineered to support a quasi-BIC in the mid-IR with a high quality factor. We tune the metasurface asymmetry to enable the optimal coupling condition that provide the highest high-harmonic generation efficiency. In the experiment, we demonstrate the generation of odd optical harmonics from the 3rd to the 11th order in the BIC regime and study their polarization dependence. We measure the dependence of the high-harmonic signal on the input intensity. The concept of metasurfaces with highly localized light boosted by BIC resonances provides a new degree of freedom to control experimentally strong nonlinear optical response.
Meta-optics based on optically resonant all-dielectric structures is a rapidly developing research area driven by its potential applications for low-loss efficient metadevices. Halide perovskite metasurfaces are of particular interest for meta-optics, as they offer unique opportunities for the light control at subwavelength scale in real optoelectronic devices. In this report, we demonstrate suppression of reflection from MAPbBr3 perovskite layer from 25% down to a few percent level by it nanostructuring and, thus, optimization of its optical response. To achieve the strongest reflectivity suppression, we employ the so-called Kerker regime when electric and magnetic Mie resonances in each meta-atom are matched properly in a broad spectral range. Our results have a high potential for application in thin-film photovoltaics where reflection reduction plays a key role in device performance.
The resonant high-index nanostructures open opportunities for control many optical effects via optically-induced electric and magnetic Mie resonances, mostly localized inside the structures. Especial interest such nanostructures represent for quantum emitters placed inside, that makes possible enhancement of quantum source emission through resonant coupling to localized modes. We have proposed the concept of active dielectric nanoantennas based on nanodiamonds with embedded NV-centers. The study of theoretically dependence of optical properties of this system on the spectral position of the resonant modes has demonstrated that that at some sizes of the diamond spherical particles and certain position of the dipole in the sphere the Purcell factor can achieve the value of 30. We have demonstrated experimentally that the photoluminescence properties of the NV-centers can be controlled via scattering resonances and observed a decrease of the NV-centers lifetime in the studied diamond particles, as compared to nonresonant nanodiamonds. These results are in a good agreement with our theoretical calculations for the average Purcell factor for multiple NV-centers within a nanoparticle. The simplicity of the proposed concept compared to existing photonic cavity systems and applicability for a wide range of color centers in diamond make active diamond nanoantenna an effective tool for creating controllable emitting elements in the visible range for future nanophotonic devices.
We demonstrate that a hybrid c-Si/Au nanocavity can serve as a multifunctional sensing platform for nanoscale (about 100 nm) thermometry with high accuracy (>0.4 K) and fast response (<0.1 second), controlled local optical heating up to 1200 K and also provide Raman scattering enhancement (>10^4 fold). The system has been tested in the experiment on thermally induced unfolding of BSA molecules, plased inside the hybrid nanocavity. Moreover, numerical modeling reveal, that two possible operation modes of the system: with and without considerable optical heating at the nanometer scale, while other functionalities (nanothermometry, RS enhancement, and tracing the events) are preserved. These regimes make the hybrid nanocavity more versatile sensing system than fully plasmonic counterparts. The simplicity and multifunctionality of the hybrid nanocavity make it a promising platform for photochemistry and photophysics applications.
Here we report theoretical and experimental results for a high-Q cavity based on nanoimprinted perovskite film. We reveal that bound state in the continuum transformed into a resonant state due to leakage into substrate leads to significant enhancement of the photoluminescence signal of the perovskite cavity.
We review a new, rapidly developing field of all-dielectric nanophotonics which allows to control both magnetic and electric response of structured matter by engineering the Mie resonances in high-index dielectric nanoparticles. We discuss optical properties of such dielectric nanoparticles, methods of their fabrication, and also recent advances in all-dielectric metadevices including couple-resonator dielectric waveguides, nanoantennas, and metasurfaces.
Gradual evolution of silicon surface topology from one-dimensional to two-dimensional nanogratings and then to isotropic sets of nanospikes was observed by increasing IR and UV femtosecond laser irradiation dose (the variable number of incident laser pulses at the constant laser fluence). The fundamental mechanisms of these topological transformations are discussed.
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